GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: rsterne on June 15, 2016, 06:21:52 PM
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Yesterday I received my mould for my new Bob's Boattail Airgun Bullets from NOE.... It is a 2-cavity aluminum mould with a Lyman style HollowPoint pin in one cavity.... I am absolutely delighted with the quality of the mould, and the bullets it produces.... First, some pics of the mould....
(http://i378.photobucket.com/albums/oo221/rsterne/Bullet%20Casting/NOE%2025%20cal%20Mould_zpsrxqltcto.jpg) (http://s378.photobucket.com/user/rsterne/media/Bullet%20Casting/NOE%2025%20cal%20Mould_zpsrxqltcto.jpg.html)
(http://i378.photobucket.com/albums/oo221/rsterne/Bullet%20Casting/NOE%2025%20cal%20HP%20Mould_zpsjyg7zdqk.jpg) (http://s378.photobucket.com/user/rsterne/media/Bullet%20Casting/NOE%2025%20cal%20HP%20Mould_zpsjyg7zdqk.jpg.html)
I conditioned it according to the enclosed instructions, used a film of Sprue lube, preheated it to about 400*F, and with my lead at just over 720*F I started casting.... I was using pure lead with about a 1.5% tin content (I had mixed roughly equal parts of 1% and 2% that I had lying around).... I discarded the first 10 bullets, and once the quality settled down I cast about 20 more.... The HPs were not filling out well, with a few wrinkles and rounded edges on the base, but the FN bullets were good for the most part, just a few with rounded corners on the base.... I dropped those bullets back into the pot, and increased the temperature to just over 760*F, and the FN bullets were then perfect, but about half of the HP still had rounded corners on the base.... You could observe this after cutting the sprue and before you opened the mould, as a slight line between the bullet and mould.... By this time I had found a tempo and method that was working well, but I still needed more heat.... I gradually increased the temperature until every bullet showed a completely filled base with a square corner, and found that required just over 800*F for the HP bullets.... The FN bullets were still casting perfectly, so that is what I found works for me.... The temperature was measured with an Infrared Digital thermometer, my dial thermometer, which I know to be out by 100*F, said just over 900*F.... I did find that overfilling the sprue on the HP moulds was necessary to get perfect corners every time.... I ended up with a sprue puddle nearly dime-sized on the HP side, but just larger than the sprue countersink on the FN worked fine....
When I sorted and examined the bullets, I ended up discarding about 30 of HP bullets, presumably the ones first cast where the temperature was not high enough.... I ended up with 115 FN and about 90 HP bullets that are virtually perfect in every way.... I then weighed and measured them and got the following results....
The FN bullets weighed an average of 50.8 gr., varying over 20 bullets from 50.6 to 51.1 gr.... The nose diameter was 0.2515", the midbody was 0.2415", and the driving band was 0.2535", with all bullets being within 0.0005" of those dimensions.... This places them 0.0015" over the design size, just about perfect to allow for sizing, IMO....
The HP bullets weighed an average of 47.8 gr., varying over 20 bullets from 47.7 to 48.1 gr.... The diameters averaged 0.0002" less than the FN bullets, so still 0.0012" over design.... I am delighted with these results.... Here is a photo of the bullets....
(http://i378.photobucket.com/albums/oo221/rsterne/Bullet%20Casting/NOE%2025%20cal%20FN%20and%20HP_zpsfb94uqbh.jpg) (http://s378.photobucket.com/user/rsterne/media/Bullet%20Casting/NOE%2025%20cal%20FN%20and%20HP_zpsfb94uqbh.jpg.html)
I am very pleased with the results of this casting session.... and look forward to seeing how they fit the magazines and barrels, and whether they need sizing.... and of course how they shoot....
Bob
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Excellent write up and guide. I look forward to reading how they shoot.
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I checked these new NOE BBTs in both my Hatsan AT-44 and my Disco Double (with .25 cal MRod magazine).... They fit both magazines fine and function perfectly.... That, of course was one of the design parameters, that the overall length fit the Hatsan mags.... and they are spot on .... Remember that I got the smaller NOE mould for these bullets, with a 0.250" nose and 0.252" driving band, but I don't think the larger ones will have any problem fitting the mags....
In the Hatsan I can feel a slight resistance on closing the lever, but they will feed fine into a stock Hatsan chamber without sizing.... I chambered one bullet and then pushed it back out, and the rifling marks are clear, and appear the same depth all the way to the rear of the driving band, so I would say the chamber has little or no tapered leade.... There were absolutely no marks on the 0.2535" driving band between the rifling marks, indicating the groove diameter of the Hatsan barrel is larger than that.... It is possible that for the best accuracy in a Hatsan, the larger (0.253/0.255") NOE mould may be the better choice, but could require cutting a longer, tapered chamber to reduce chambering force.... If you don't want to do any barrel work, the smaller (0.250/0.252") NOE mould, like I got, may be the better choice....The Hatsan was tuned for 70 FPE with JSB King 34.2 gr. Heavies, and shot 75 FPE with the 50.8 gr. FN BBTs (815 fps).... I did not try increasing the hammer spring preload as that is not the gun I bought them for.... I have the 41 gr. BBT mould with the larger 0.253" nose / 0.255" driving band coming for the Hatsan.... and I now know I will likely have to cut a tapered leade for them....
In the .25 ACP liner by TJ's in my Disco Double, there was a fair amount of resistance closing the bolt, indicating they are slightly large for the chamber I have.... Once sized, they fed easier than the unsized ones in the Hatsan, basically no more resistance than chambering a JSB King Mk2 Heavy, and easier than the original King Heavy pellets with the oversize skirts.... I maxed out the hammer spring preload in the Disco Double, and tethered at 2900 psi they screamed over the Chrony at 1007 fps (114 FPE).... I backed the preload out 2.5 turns, and got the following average velocities for 5 shots....
50.8 gr. FN BBT unsized - 940 fps (100 FPE)
50.8 gr. FN BBT sized - 960 fps (104 FPE)
47.8 gr. HP BBT unsized - 965 fps (99 FPE)
47.8 gr. HP BBT sized - 985 fps (103 FPE)
Note that the velocity increased 20 fps with sizing the bullets, a good indication they are a bit tight as cast.... All four 5-shot groups that I fired through the Chrony were ragged holes in the backstop at 20 feet.... They all shot tighter during Chrony testing than the .25 cal 51 gr. BBTs I cast from my LBT mould, and a lot tighter than the 52.7 gr. RN Lyman 57902, or its HP version which was 46.4 gr.... I never found a setup that grouped with the Lymans.... It may be some time before I can get to try the new NOEs at long range, unfortunately....
When I size these bullets, there is just a hint of contact with the sizing die on the nose, enough to polish it all the way around, and the driving band is definitely smaller (now the same size as the nose, of course), but slides easily through my 0.250" sizing die.... When chambered in my Disco Double, which has a tapered leade of 2* per side, the nose is evenly, but not deeply marked by the rifling, as is the driving band.... I would say that sizing to 0.250" is just about perfect in the TJ's barrel.... I plan to size all my bullets prior to any further testing....
One other thing, I tried chambering these bullets in a .25 cal Lothar Walther barrel I bought many years ago from Mountain Air.... This barrel was chambered for pellets, and I am sure could benefit from having a longer chamber and tapered leade cut for use with bullets.... I could barely chamber an unsized bullet, but sized to 0.250" it chambered smoothly until it came up against the rifling (obviously no, or very little, taper in the leade), and the last 1/8" you had to give the bolt a firm shove to chamber it.... I understand the earlier LW barrels (which mine is) are smaller than the current production, which is listed on the LW website as 0.248" land and 0.254" groove.... If the specs on the website are correct, I think the larger size NOE mould (0.253" nose / 0.255" driving band) would be the better choice....
Now what we need are more readily available sizing dies in airgun calibers.... Al, are you listening?.... ???
Bob
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That is an excellent report Bob, and nice work on the first run. I'll have my mood once I get home and can't wait to run a batch. I did get the .253/.255 for my BT65 with the choke removed . Will post once I figure out the casting process ( complete newbie ) . By the way thanks for the tip on temps , that should give me a good starting point.
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I think you will have to do some work on the chamber to make the (larger size) bullets chamber properly.... I would imagine just tapering the front of the chamber to form a proper leade is all that will be needed.... There is no reason that with care this should hamper the loading and use of pellets.... You may (or may not) need a short parallel section where the skirt of a pellet will sit when chambered.... That is what I do when I am chambering a barrel for both pellets and bullets.... The head of the pellet (and nose of the bullet) engages in the tapered leade when chambered....
Bob
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I have also received this mold. The bullets cast with it look great. In my Condor SS with the TT heavy hammer and adjustable top hat, at a 3000 psi fill, at any spring power setting, they shoot 865-ish fps on the first shot, steadily decreasing to about 805 on shot 10. I have not done any comprehensive accuracy test yet, but they seem to go exactly where I aim them, and aluminum cans at 50 yards are hit every time. The hollow points will nearly go through 3 gallon jugs filled with water. They crack the back wall on the last jug, but do not make it through. They expand to just over .30". The solid nose bullets go through three jugs. These are the heavy plastic windshield washer fluid jugs, not the thin plastic milk jugs if that really makes a difference. The mold I have is for .253/.255 diameter, the bullets fit tight enough in the chamber that I have to use a flat tool to push them all the way in to the rifling.
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Bob, is there any chance you are able to draw up a 50 gr version BBT in .257 and add it to the NOE list? Or would the .253 version be big enough for a .257 barrel? I just put my name in for a 65gr .257 at NOE. Hopefully a few more get on board the BBT train.
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I did some penetration testing today in my standard media, which is clear "Melt and Pour" Soap, cast into blocks.... This material will stop a HV .22LR RN bullet in less than 11", and shows expansion of HollowPoint bullets well enough to photograph the cavity, and allow the bullet to be recovered.... It is harder than Ballistics Gel, but the wound cavity retains its shape after impact, and it's nowhere near as hard as Paraffin Wax or Phonebooks.... Here is the comparision between the 50.8 gr. FN and the 47.8 gr. HP, both shot at 100 FPE....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/25%20cal%2051%20gr%20NOE%20BBTs_zpsazje5llc.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/25%20cal%2051%20gr%20NOE%20BBTs_zpsazje5llc.jpg.html)
The FN bullet penetrated 155 mm (6.1") and the HP penetrated only 85 mm (3.3") but created a much wider wound channel.... Here is the cavity created by the HP bullet, which broke into 6 pieces....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/HP%20Cavity_zpscloonc0j.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/HP%20Cavity_zpscloonc0j.jpg.html)
and here are the recovered bullets.... The FN expanded to larger than bore size.... The HP expanded well, with the nose portion coming apart....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Side%20and%20Front_zpsejc5kmlc.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Side%20and%20Front_zpsejc5kmlc.jpg.html)
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Front%20and%20Back_zpsi21tephi.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Front%20and%20Back_zpsi21tephi.jpg.html)
Although the HP cavity is only 1/8" in diameter and about 3/16" deep, it certainly does its job.... I am very pleased with how these bullets performed....
Bob
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deadguy.... if you push a bullet back out after chambering, what does it look like?.... If there are no marks on the driving band between the rifling, the bullet is the right size, you just need a bit of work on the chamber....
tnt76.... I can draw up a 50ish gr. version in .257, but I don't think you would have much luck getting a Group Buy going on one.... Most .257 shooters seem to start at about 65 gr. and go up from there.... The larger version of the 50 gr., at 0.255" on the driving band, and assuming they are about 0.0015" over like the smaller one, might just work OK in a .257.... The other alternative is to ask Al to make you a mould of the existing design at 0.257/0.259".... They have the ability to make moulds larger than the pattern, the problem is finding the time to run a single order.... In other words it CAN be done, but you might have to wait for it.... I would PM Al Nelson at NOE (SwedeNelson) and tell him what you want.... you never know, it can't hurt....
Bob
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I have not tried hammering one back out after chambering it, but I did recover one that was fired into a row of water jugs. The rifling marks were deep, but they were only on the front and rear driving bands, not on the central body. I have heard that the chamber on the AirForce barrels is a little short for these types of rounds, but it seems to work. It just takes a little bit longer to load.
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I have not tried hammering one back out after chambering it, but I did recover one that was fired into a row of water jugs. The rifling marks were deep, but they were only on the front and rear driving bands, not on the central body. I have heard that the chamber on the AirForce barrels is a little short for these types of rounds, but it seems to work. It just takes a little bit longer to load.
It almost looks just long enough to use a bore riding nose..? would ease chambering a bit if you size the nose... should be just as accurate if you have the right size bushing...
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What you are looking for is a mark on the driving band BETWEEN the rifling marks, to see if the driving band is larger than the groove diameter of the barrel.... If that area is clearly smaller than before chambering, then basically the barrel is sizing the bullet, which is not great.... It would be better to size the bullet before using it.... If there are no marks on the drive band between the rifling marks, then the bullet, as cast, is not too large, and the reason for the difficulty chambering is not that the bullet is too large, it is that the chamber is too short, or there isn't enough angle on the leade between the chamber and rifling.... Since your barrel was intended for pellets (at least I assume that), it may have little to no chamber, and little to no leade.... That is OK for pellets, but makes bullets hard to load.... A good chamber will work with both....
K.O.... I would not size the nose all the way down to the land diameter, as a bore rider, as then you would only have the full support in the very short driving band.... these BBTs are intended to work somewhat like a pellet.... The back of the nose, and the driving band, should have good rifling marks.... but the midbody between them should clear the lands (barely) to reduce drag....
Bob
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So how can the chamber be fixed? Do I need to live with using a tool to load, or consider getting a new barrel?
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Not a true bore rider; size just a bit loose with just a thin small band of groove contact... it would take some in between sizes like say .248 / .248+ / . 249 and so on...of course the rear band still needs be just past groove size...
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The best way is to find someone with a chambering reamer.... You can likely work it over yourself with some 400 grit wet-or-dry on a split dowel mandrel.... less work deeper and more towards the back.... to create a bit of a taper in the rifling.... W.A.R. could likely do the job for you....
Bob
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oops meant groove size edited my above post
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I've never bought a mold before, but would like to buy this one.I would want both HP and FN in one mold. Is everything needed (as in the photo above) included, or are those parts extra? Why choose brass over aluminum or vice versa? Why two cavity over four?How would I describe what I want, when ordering? I would be thankful for all help anyone can give me on this.
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You don't get the handles included in the Mould price.... NOE sell handles for their moulds, or you can use the less expensive Lee 6-cavity handles.... However, you may find they are slightly tight in the grooves in the side of the mould (mine were), and have to grind them just slightly thinner.... You don't want them to bind in the mould, loose is better than tight.... The NOE moulds come with the Sprue Plate and all the mounting hardware.... Get the Sprue Plate Lube and wrenches (cheap) when you buy the mould....
The mould is available with the Lyman style HollowPoint pin (as shown) at extra cost.... It will only be in ONE cavity, regardless of how many cavities the mould has (2 to 5).... I have always used aluminum moulds, but I understand brass holds the heat better, but is much heavier, particularly in the bigger moulds.... NOTE there are two sizes available in this mould.... 0.250" nose with 0.252" driving band.... OR 0.253" nose with 0.255" driving band.... If you have the .25ACP liner from TJ's, you want the smaller size.... I THINK for the Hatsans and LW barrels you will want the larger size, but they may vary.... I have been told that an MRod barrel is 0.254" groove, and if that is the case, you would want the larger size.... Bullets can always be sized smaller, you can't make them bigger....
If you end up having to size your bullets (lets face it, eventually you will want to at least try that), all you need is an inexpensive Lee press.... Lee make dies, and you can order custom sizes, but if you want a custom size, I would have used Doughty, but they have discontinued dies.... I am working with Al Nelson at NOE to get him to make sizing bushings for his die for airgun sizes.... No idea when that will happen yet....
The NOE Store is pretty easy to follow along.... Start here to choose which mould you want, and then it should be a typical online shopping experience....
http://noebulletmolds.com/NV/index.php?cPath=374_376 (http://noebulletmolds.com/NV/index.php?cPath=374_376)
If you have any questions, just ask, or PM me on either this Forum or the NOE Forum....
Bob
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Thank you Bob, The options: what is drill for probe? My hand loading press is a Dillon, so I would want the Lyman/ RCBS top punch? I'm assuming the Top Punch is used for pushing this bullet through a sizing die, that I would get some place else?
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Hi Bob, I just looked over on Cast Boolets and your links answered my drill for probe question. I think I will end up needing both mold sizes, as I have .25cal barrels from different makers and they do seem to vary in bore size. Very interested in what you come up with for sizing dies for airgun bullets. Thank you Sir,
Terry
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Bob, i am up in colorado with tofazfou and Monkeydad but we shot the bbt mold in fp and hp. My Cricket drilled hole in hole at 50 yards. My talon p ss did not due so well but the escape did ok with them .
In my Cricket the HP were good but not as good as the fp. I going to do some testing but preliminary results look promising.
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well me in the end to get cast running their best off air I will be doing some knurling of the rear band and maybe noses contact point after sizing...
I will probably see first with the redneck two file method and I think I can develop the touch...maybe make a plexi uchannel and bolt the top file to it for more consistency adjust to final size with washers/shims...
could just buy the Corbin knurling fixture... but I am to redneck to always/some times ;) do it right...
I really do think if done right it will help the rounds in the choked barrels... may do well in the unchoked barrels also...
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25ACP - I am pretty sure the "drill for probe" is for a temperature probe to measure mould temperature, just a guess, really.... A top punch allows you to size a bullet base first, it fits the nose of the bullet to not damage it.... I think with the rebated boattail design you can size just as well pushing it through nose first, and because my BBTs from NOE have a 0.002" smaller nose than drive band, they should push through straight.... I size using a Lee press, nose first.... seems to work great!....
Nick that is great news on the groups.... If you think of it, please take a photo of the groups from the Cricket, I would like to post them on the NOE Forum....
Bob
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Bob, i did not take a picture this was just a preliminary while we were hunting. I will take pics when I do real testing.
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Thanks Bob for posting this. Looks like exactly what I need for my ace. The eujins shoot well but have a bit of quality control issue as well as the hunter supply 49 grain. Inconsistent base on those and have to really pick through them for consistent accuracy. I have some bt for my .35 and they are stellar. I don't have casting equipment but as soon as someone has them for sale, I'm definitely a buyer. Not a lot available in the 252-253.
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I got a chance to do some velocity testing at 50 yards today, so I was able to calculate the Ballistics Coefficient for the new NOE Bob's Boattails.... I tested five bullets, the RN and HP version of the Lyman 57902 bullet for .25 ACPs, the BBT I designed for LBT Moulds, and the new BBT I designed for NOE.... I also tested the JSB King pellets.... I used two (calibrated) chronographs, at 1 yard and 51 yards from the muzzle, and then calculated the BC, corrected for the pressure, temperature, and altitude of the tests, to NPT conditions.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/25%20cal%20BCs_zps5koha48k.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/25%20cal%20BCs_zps5koha48k.jpg.html)
The difference in the BC with the boattail bullets is significant.... about 30-33% improvement compared to the flat based .25 ACP bullet from the Lyman mould.... The new NOE bullets had an 11% better BC than the almost identical BBT I cast using the LBT moulds, which have a smaller Meplat.... This confirms that there is no disadvantage to having a Meplat as large as 70% on relative short bullets, as proven many years ago by Elmer Keith.... It is interesting what happened with the 25 gr. JSB King pellets.... The way my Disco Double was tuned for the testing today, it blasted the Kings out at over 1200 fps.... What was astounding is that they arrived at 50 yards going only a bit faster than the bullets.... This confirms two things.... 1. That pellets have a poor BC.... and 2. that Supersonic velocities cause pellets to slow down at an extreme rate.... At 50 yards, the Bob's Boattails still had about 78 FPE of energy, but the Kings were down to just 43 FPE....
I then proceeded out to the ranch where I do my Varmint hunting.... I wanted to see how the 47.8 gr. NOE HP Bob's Boattail performed.... All I can say is, that headshots are no longer required, in fact the recovery rate is greater with a shot to the chest.... Not only do you have a much bigger target, but the bullet does a huge amount of damage as it passed through the quarry.... accompanied by a large spray of blood, clearly visible in the scope, and a loud WHACK! as the bullet hits.... Photos of the exit wounds on a Marmot and a Ground Squirrel, both taken at about 50 yards, will be in the hunting gate....
Bob
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I got a chance to do some velocity testing at 50 yards today, so I was able to calculate the Ballistics Coefficient for the new NOE Bob's Boattails.... I tested five bullets, the RN and HP version of the Lyman 57902 bullet for .25 ACPs, the BBT I designed for LBT Moulds, and the new BBT I designed for NOE.... I also tested the JSB King pellets.... I used two (calibrated) chronographs, at 1 yard and 51 yards from the muzzle, and then calculated the BC, corrected for the pressure, temperature, and altitude of the tests, to NPT conditions.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/25%20cal%20BCs_zps5koha48k.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/25%20cal%20BCs_zps5koha48k.jpg.html)
The difference in the BC with the boattail bullets is significant.... about 30-33% improvement compared to the flat based .25 ACP bullet from the Lyman mould.... The new NOE bullets had an 11% better BC than the almost identical BBT I cast using the LBT moulds, which have a smaller Meplat.... This confirms that there is no disadvantage to having a Meplat as large as 70% on relative short bullets, as proven many years ago by Elmer Keith.... It is interesting what happened with the 25 gr. JSB King pellets.... The way my Disco Double was tuned for the testing today, it blasted the Kings out at over 1200 fps.... What was astounding is that they arrived at 50 yards going only a bit faster than the bullets.... This confirms two things.... 1. That pellets have a poor BC.... and 2. that Supersonic velocities cause pellets to slow down at an extreme rate.... At 50 yards, the Bob's Boattails still had about 78 FPE of energy, but the Kings were down to just 43 FPE....
I then proceeded out to the ranch where I do my Varmint hunting.... I wanted to see how the 47.8 gr. NOE HP Bob's Boattail performed.... All I can say is, that headshots are no longer required, in fact the recovery rate is greater with a shot to the chest.... Not only do you have a much bigger target, but the bullet does a huge amount of damage as it passed through the quarry.... accompanied by a large spray of blood, clearly visible in the scope, and a loud WHACK! as the bullet hits.... Photos of the exit wounds on a Marmot and a Ground Squirrel, both taken at about 50 yards, will be in the hunting gate....
Bob
BoB,
Had a chance to see the 250 BBT's while out with Joe in Colorado this past week. They are very nice looking bullets and when i took a look at them, it made me want to get my 25 cal gun up and running even more than i already do now (if there is such a thing). Nick Nielsens Casting and your design for sure make for a nice looking projectile and the HP mouths are HUGE to say the least. Joe is having good luck with them.
Also, i like the numbers im seeing from your testing. The FN versions have a BC not too far off from the 70 gr Lyman .257420 at .129 and that is AWESOME news for the guys with 250 airguns that might not want or need a 257.
That is some significant drop from the hypersonic JSB but not surprising at all. Those are good numbers for all to see as a constant reminder that diabolo pellets do have a PARACHUTE attached to the back of them..........;)
GREAT STUFF BOB! 8)
Tofazfou
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I'm glad guys are having success with the new NOE BBTs.... Any time you change a design, or redesign, there is always a risk.... Using that larger Meplat, to shorten the bullet so that it will fit a Hatsan magazine as well as the MRod mags.... and having the BC actually improve over the previous bullet from LBT was a bonus....
I don't think there is much question that boattails really help reduce the drag and improve the BC to a greater degree Subsonic and Transonic than they do Supersonic.... Most guys told me I was nuts a couple of years ago when I suggested it.... but a BT only reduces the drag at Mach 3 by 10-15% at most.... At airgun velocities we are seeing improvements of about 25-35%, with BCs often improving by a third.... These latest NOE BBTs end up with a Form Factor of just over 1.... For the HP it is 0.109 / 0.101, and for the FN it is 0.116 / 0.107, which in both cases works out to 1.08.... The LBT was only 0.116 / 0.096 = 1.20.... and the .25 ACP RN flat base bullet was only 0.120 / 0.083 = 1.45.... That is a 34% advantage for my NOE boattails.... For the Lyman 257420, using your BC, it works out to 0.151 / 0.129 = 1.17.... I'm really looking forward to finding out what the BC of the boattail version of that a bullet I designed works out to.... You have some, don't you?.... *poke*....
BTW, when I get some time I plan to take some BC measurements of the King and King Heavy pellets in smaller increments, to show what happens in the Supersonic and Transonic regions, compared to below 900 fps.... I think it will open a lot of eyes....
Bob
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I'm glad guys are having success with the new NOE BBTs.... Any time you change a design, or redesign, there is always a risk.... Using that larger Meplat, to shorten the bullet so that it will fit a Hatsan magazine as well as the MRod mags.... and having the BC actually improve over the previous bullet from LBT was a bonus....
I don't think there is much question that boattails really help reduce the drag and improve the BC to a greater degree Subsonic and Transonic than they do Supersonic.... Most guys told me I was nuts a couple of years ago when I suggested it.... but a BT only reduces the drag at Mach 3 by 10-15% at most.... At airgun velocities we are seeing improvements of about 25-35%, with BCs often improving by a third.... These latest NOE BBTs end up with a Form Factor of just over 1.... For the HP it is 0.109 / 0.101, and for the FN it is 0.116 / 0.107, which in both cases works out to 1.08.... The LBT was only 0.116 / 0.096 = 1.20.... and the .25 ACP RN flat base bullet was only 0.120 / 0.083 = 1.45.... That is a 34% advantage for my NOE boattails.... For the Lyman 257420, using your BC, it works out to 0.151 / 0.129 = 1.17.... I'm really looking forward to finding out what the BC of the boattail version of that a bullet I designed works out to.... You have some, don't you?.... *poke*....
BTW, when I get some time I plan to take some BC measurements of the King and King Heavy pellets in smaller increments, to show what happens in the Supersonic and Transonic regions, compared to below 900 fps.... I think it will open a lot of eyes....
Bob
I have been using King heavies and I'm happy with them ...... but I'm waiting to see your test ... I think I may change my hunting pellets to your design as it will GREATLY turn my already very powerful Condor .25 into a Raving Monster of a varmint gun for sure ... this I think could be a real game changer !!! nice going Bob !
wll2506
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I'm glad guys are having success with the new NOE BBTs.... Any time you change a design, or redesign, there is always a risk.... Using that larger Meplat, to shorten the bullet so that it will fit a Hatsan magazine as well as the MRod mags.... and having the BC actually improve over the previous bullet from LBT was a bonus....
I don't think there is much question that boattails really help reduce the drag and improve the BC to a greater degree Subsonic and Transonic than they do Supersonic.... Most guys told me I was nuts a couple of years ago when I suggested it.... but a BT only reduces the drag at Mach 3 by 10-15% at most.... At airgun velocities we are seeing improvements of about 25-35%, with BCs often improving by a third.... These latest NOE BBTs end up with a Form Factor of just over 1.... For the HP it is 0.109 / 0.101, and for the FN it is 0.116 / 0.107, which in both cases works out to 1.08.... The LBT was only 0.116 / 0.096 = 1.20.... and the .25 ACP RN flat base bullet was only 0.120 / 0.083 = 1.45.... That is a 34% advantage for my NOE boattails.... For the Lyman 257420, using your BC, it works out to 0.151 / 0.129 = 1.17.... I'm really looking forward to finding out what the BC of the boattail version of that a bullet I designed works out to.... You have some, don't you?.... *poke*....
BTW, when I get some time I plan to take some BC measurements of the King and King Heavy pellets in smaller increments, to show what happens in the Supersonic and Transonic regions, compared to below 900 fps.... I think it will open a lot of eyes....
Bob
I have been using King heavies and I'm happy with them ...... but I waiting to see your test ... I think I may change my hunting pellets to your design as it will GREATLY turn my already very powerful Condor .25 into a Raving Monster of a varmint gun for sure ... this I think could be a real game changer !!! nice going Bob !
wll2506
I will testify to it making the Condor .25 into a monster of a varmint gun! I took a starling with this bullet in my Condor SS, and the impact of the bullet hitting the starling in the center of the chest sounded like a .22lr rifle being shot. It dropped then and there, it did not feel a thing. This bullet is a very humane pest getter!
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I'm glad guys are having success with the new NOE BBTs.... Any time you change a design, or redesign, there is always a risk.... Using that larger Meplat, to shorten the bullet so that it will fit a Hatsan magazine as well as the MRod mags.... and having the BC actually improve over the previous bullet from LBT was a bonus....
I don't think there is much question that boattails really help reduce the drag and improve the BC to a greater degree Subsonic and Transonic than they do Supersonic.... Most guys told me I was nuts a couple of years ago when I suggested it.... but a BT only reduces the drag at Mach 3 by 10-15% at most.... At airgun velocities we are seeing improvements of about 25-35%, with BCs often improving by a third.... These latest NOE BBTs end up with a Form Factor of just over 1.... For the HP it is 0.109 / 0.101, and for the FN it is 0.116 / 0.107, which in both cases works out to 1.08.... The LBT was only 0.116 / 0.096 = 1.20.... and the .25 ACP RN flat base bullet was only 0.120 / 0.083 = 1.45.... That is a 34% advantage for my NOE boattails.... For the Lyman 257420, using your BC, it works out to 0.151 / 0.129 = 1.17.... I'm really looking forward to finding out what the BC of the boattail version of that a bullet I designed works out to.... You have some, don't you?.... *poke*....
BTW, when I get some time I plan to take some BC measurements of the King and King Heavy pellets in smaller increments, to show what happens in the Supersonic and Transonic regions, compared to below 900 fps.... I think it will open a lot of eyes....
Bob
I have been using King heavies and I'm happy with them ...... but I'm waiting to see your test ... I think I may change my hunting pellets to your design as it will GREATLY turn my already very powerful Condor .25 into a Raving Monster of a varmint gun for sure ... this I think could be a real game changer !!! nice going Bob !
wll2506
I will testify to it making the Condor .25 into a monster of a varmint gun! I took a starling with this bullet in my Condor SS, and the impact of the bullet hitting the starling in the center of the chest sounded like a .22lr rifle being shot. It dropped then and there, it did not feel a thing. This bullet is a very humane pest getter!
Did you make your own Bob's slugs or did you buy them ? And if you bought them, from who ;- )
wll2506
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I have been using King heavies and I'm happy with them ...... but I'm waiting to see your test ... I think I may change my hunting pellets to your design as it will GREATLY turn my already very powerful Condor .25 into a Raving Monster of a varmint gun for sure ... this I think could be a real game changer !!! nice going Bob !
wll2506
I will testify to it making the Condor .25 into a monster of a varmint gun! I took a starling with this bullet in my Condor SS, and the impact of the bullet hitting the starling in the center of the chest sounded like a .22lr rifle being shot. It dropped then and there, it did not feel a thing. This bullet is a very humane pest getter!
Did you make your own Bob's slugs or did you buy them ? And if you bought them, from who ;- )
wll2506
I made mine. I bought the mold when it was offered as a group buy on the NOE forums.
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Man guys I am a bit of a pain but would love to hear barrel/fpe info... I know the Dor SS stock is a L.W. barrel (is it really 1:16 like PAs info and not 17.7) I know also it came in different lengths... are they choked? # lands/grooves are Probably same as the L.W. specs... as well as would be width and height... Barrel Diameter?
But I know nothing of the Cricket other than I think the barrel are made by CZ which means hammer forged...the CZ American .22 lr barrel is tight and seems choked... the one that an acquaintance has... I forgot how many lands and grooves and thier specs... besides this is a different barrel air and .25
I know Bob published the specs on his TJ liner some where so I will look...
The Hatsans are stock L.W. ..? Diameter?
Me I am going with the 40g BBT to try in a stock .25 mrod with maybe a heavier spring... Not sure the Mrod breech is solid enough for more than 60-80 fpe... would like to see 6 bolts rather than 4..? besides I want to stick with hand pumping... can deal with only getting 3-5 shots per fill...before pumping back to 3000 psi... Hoping it works out not having to do a bunch of mods will allow many more to enjoy the benefits of higher BCs...
I would like to lobby for a Wildcatters Lodge/Corner/Lounge Gate with small and large bore sections... what is being done is pretty new and having the info gained on what works and does not and possible fixxes in one place would help move things forwards...
Bob I do have some questions about design trade offs and such... and thanks for drawing up the lights also...
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knowing if you are sizing and how or able to run as cast would be nice.. ;)
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As cast, from the 0.250" nose / 0.252" drive band (smaller) NOE mould, which drops 0.0015" oversize, they are a bit tight in a TJ's barrel.... slightly hard to chamber in a 2* leade, where the rifling is partially engraved on the drive band.... When I sized them, I picked up nearly 20 fps, and they chamber like a pellet, so IMO that means they need sizing.... My die is 0.250".... made by grinding out a Lee .243 die....
Bob
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I decided to try the o-ring trick on my Condor SS with these bullets, and here are the results, with a #36 o-ring under the top hat. My Condor SS is also equipped with the TT Quick Change top hat with no insert, and the TT heavy hammer with slap mod.
Shot# Velocity Power level
1. 742.5. Full
2. 718.2. Full
3. 710.3. Full
4. 724.7. Full
5. 716.6. Full
6. 737.7. Full
7. Error. Full
8. 720.4. Full
9. 718.4. Full
10. 719.2. Full
11. 721.9. Full
12. 733.3. Full
13. 723.6. Full
14. 725.5. Full
15. 714.7. Full
16. 735.7. Full
17. 710.0. Full
18. 732.9. Full
19. 701.5. Full
20. 710.9. Full
21. 719.6. Full
22. 715.1. Full
23. 720.3. Full
24. 730.2. Full
25. 732.9. Full
26. 730.7. Full
27. 709.2. Full
28. 734.4. Full
29. 753.6. Full
30. 751.2. Full
31. 703.4. 6-0
32. 697.7. 6-0
33. 697.0. 9-0
34. 694.8. 9-0
35. 686.0 Full
36. 700.0. Full
37. 696.4. Full
38. 689.9. Full
39. 700.1. Full
40. 701.7. Full
I stopped at 40 shots because that was how many of these 51 grain flat nose BBTs I had ready, and because my Condor was down to 2000 psi. But it is looking like this tune setup plus these cast bullets make a powerful and economical plinker and hunter! 40 shots around 60 ft-lbs each is not bad at all.
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Really it become a small cannon. Congratulations.
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I have high hopes for this bullet because my Cricket really liked them on my original test at 50 yards.
To each his own on how they test and evaluate but there is a lot of testing on ES and fps over the chrony, etc. I do not bother with any of that until I find out if the bullet is accurate or not. I would take an accurate bullet over one with twice the BC or better ES all day long. Who care what any of that is if you can't hit *hit with it.
I am trying to get out and shoot tomorrow but I got lots going on this week since I was gone last week hunting and Burrow Canyon Shooting Range where I shoot has been closed due to the forest fires here in Los Angeles. We need to shoot groups at 50 and 100 yards out of multiple guns and barrels to see if this bullet is any good.
I just installed a scope on my Sumatra and I will bring my Cricket as well. I am hoping others will get groups shot and post results. I will take pics of the groups I shoot when I get them done.
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I got my 4 cavity BT W/HP today. This is my first mold , but it looks perfectly machined. I have 50 pounds of pure lead coming and I have to make a decision on a lead pot. I love the "pro" model RCBS, but that's a lot of cash. I'm probably going to start out with the Lee 20#, unless someone here can give me a better alternative? Beautiful little bullets Bob!
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Let me start by saying I was excited to shoot this bullet today hoping it was going to go on my casting machine. I did shoot a really nice 5 shot group with it last week out of the same gun. I was very disappointed after shooting today.
I took the BBT out today sized .250 and .252. I shot the .250 and the .252 out of my Sumatra and I shot the .250 out of my Cricket.
I started with the Sumatra. The groups were horrible at 50 yards and I missed target completely on some of the shots. I shot both the .252 sized and the .250 sized bullets. I did not even bother with 100 yards. Some of the bullets were key holing as well. The first picture shows the Sumatra at 50 yards. Left target was .252 FP and the right was .252 HP. The .250 was just as bad but no pic. Also keep in mind I shot more bullets than what the target shows but they missed the target.
I then set up the Cricket at 50 yards. No where near the results I got the other day which I was very happy with at 50 yards. These were not horrible but not good either. It was windy which plays into the accuracy but a good slug can buck wind much better than a pellet and the target was only 50 yards away. In the 2nd picture the left is the FP and the right is the HP bullets. The FP shot better for sure out of my Cricket.
** Wind was left to right and not terrible wind but was not calm for sure and got worse the later it got **
At 100 yards this bullet was shooting all over. The target was not always shot so the groups are hard to tell since it missed the target in some cases. Some of the bullets were key holed and some looked straight (most). Left top is the FP and bottom left are the HP at 100 yards in the 3rd pic. It really shot all over the place and the bullet does not seem to be stable in either gun.
For reference I also shot JSB Diabolo to get an idea of the wind as well as my 34 grain swaged slug. The last picture (4th) shows top left with JSB which this rifle can shoot much much better but the later it got the worse the wind was. The last bullet I shot was my 34 grain swaged slug on top right. This was minutes after shooting the pellets so the wind was about the same and you can see what a slug can do to buck the wind vs a pellet. The one bullet at the bottom (5o'clock) of the top right target was a sight in shot. This slug can do moa with no wind in the Cricket but not possible today.
As for BC I did use my Labradar to get an idea of that as well.
Sumatra with BBT 51 gr: 0.0998
Cricket with BBT 51 gr: 0.113
Cricket with JSB 25.39 gr: 0.034
Cricket with NSA 34 gr: 0.083
Here is muzzle velocity of the BBT 51 out of my Cricket:
755
786
781
788
782
778
777
768
790
764
*** ES 34.04 fps
*** Std Dev 11.14 fps
Here was muzzle out of same gun with my 34 grain swaged:
878
876
876
875
875
873
874
877
877
875
878
873
876
873
877
875
875
876
874
876
877
*** ES 4.59 fps
*** Std Dev 1.39 fps
Although the 34 grain slug had a lower BC it very much out performed this bullet in wind deflection and overall accuracy. I thought I would be making a much different post here but the results are what they are. I hope others can get fantastic results out of their guns so we know which guns like this bullet likes and which ones is does not. I am still on the hunt for a .250/.252 bullet in this weight range.
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Like you say, Nick, it is what it is.... Have you any idea what the twist rates are in the Sumatra and Cricket?.... When you shot the good groups the other day from the Cricket, were they "as cast" or sized?.... I didn't try at 100 yards, but the results from my TJ's 14" twist barrel during Chrony testing (and I was not shooting for groups) were better than what your Cricket was shooting at 50 yards on the above target.... The BC in your Cricket was similar to what I found, a bit better, probably from the lower velocity.... The fact it was lower in the Sumatra is likely because it was wobbling....
Bob
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The Cricket was 1:17.7 and the Sumatra is 1:20
Those groups would be better if the wind was not so blowing so much but that is why I also shot a diabolo pellet and one my proven slugs for comparison which neither shot as well as they can either because of the wind.
I went home deflated. I really thought I was going to come home and order that mold for the casting machine.
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This is the reason I don't have a huge selection of bullets for sale. If I shoot them and they don't shoot well for me I don't sell them. I have countless designs I have swaged or bought molds for that did not work. This is just one of hundreds that did not work so for me this is just part of the daily grind trying to find ammo that works in our airguns.
Honestly Bob, my opinion for what it is worth (very little I know) I think the BBT design only works in long, heavy bullets. I bet if this same design was 70 grains and the gun had enough power to fire it, it would be an accurate round.
I know when the .357 BBT were tested by the guys I shoot with here in So Cal the 90's grain did not shoot well, the 110 grain was OK and 126 grain was much better. I am not talking about BC or SD or any theory but actual testing on paper.
It is just my guess that small stubby BBT do not shoot well in air guns but the longer and heavier ones show promise. I think I will focus more on those in the future because I believe in the boattail designs but they don't seem to work in the short bullets. I get the same results in the swaged bullets I make. That is why I make with a short boattail with good results when I swage them.
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I am not at all surprised that the bullet did not stabilize in a 20" twist.... Even 17.7" is on the slow side.... I am recommending a 14", although it should do just fine in anything 16" or faster.... Here are the Stability Curves, from the Kolbe Twist Calculator
(http://i378.photobucket.com/albums/oo221/rsterne/Bullet%20Casting/25%20cal%2051%20gr%20NOE%20BBT%20Twist_zpskp6iixln.jpg) (http://s378.photobucket.com/user/rsterne/media/Bullet%20Casting/25%20cal%2051%20gr%20NOE%20BBT%20Twist_zpskp6iixln.jpg.html)
The chart above shows twist for a Stability Factor of 1.5 (ideal).... As you can see, even at low velocities, the slowest twist is about 18"....
(http://i378.photobucket.com/albums/oo221/rsterne/Bullet%20Casting/25%20cal%2051%20gr%20NOE%20BBT%20SF16_zpsvbjs3d59.jpg) (http://s378.photobucket.com/user/rsterne/media/Bullet%20Casting/25%20cal%2051%20gr%20NOE%20BBT%20SF16_zpsvbjs3d59.jpg.html)
The second chart shows the Stabilty Factor in a 16" twist barrel.... optimum at about 1000 fps or below....
You may be entirely correct about BTs not working well in short stubby bullets, or it may well be that the theory is correct, and you need faster twists with boattails.... I guess time, and more experience and testing, will tell.... I certainly value your opinion.... and the coolest thing is that you won't make and well bullets you aren't happy with.... I admire you for that, 100%.... 8)
The MRods should be a good test, with their 15.5" twist barrels.... BTW, this .25 cal in 51 gr. is 1.67 cals long, the .357 cal 127 gr. is only 1.5 cals.... and I agree, the 90 gr. and 110 gr. .357 cals were simply made to fit magazines and are extremely short.... I think that 1.5 cals long may be about the minimum to make sense in a BBT, but again, time will tell....
Bob
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Bob -
The smaller 41gr .25 cal BBT should stabilize in up to a 1:22 - correct?
Nick -
Why don't you try that one?
Bob -
I think there may be a market for a .25 cal bbt @~47gr (1.5 cals) for the 1:17 to 1:20 twist bbls
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Match
Based on my testing so far with hundreds of designs of bullets I start to get a feel of what works and what does not. Of course, mainly influenced by the guns I own or have access to. I believe these boattail designs only work when the bullet is long and heavy. The bullet you want me to try is even shorter than the one I already tried.
It is not just the BBT. Same thing when I swage a full length boattail - they are not stable. Bob could be right and you need a very fast twist rate to stabilize it. Problem with that is most guns do not have that and I make ammo for "most" guns not for a few custom guns. So if you need a 14 twist or faster to do so, I do not know of any barrels on production guns for .250-.252 with 10-14 twist rates so only a few guys who rebarrel or have customs guns could potentially buy it from me.
I hope I am wrong because no one wants this to work more than me, except maybe Bob :).
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or me...
It looks like we both want something that works with slow twists....
I want to use both pellets and slugs in the same bbl.
Both the GM bbl and TJ's .25ACP liner are 1:14.
I may wind up staying 1:14 but I think this over-stabilizes the pellets beyond 75 or 100 yrds making it very hard to have a low cost long range (100+yrds) target practice gun - which is my primary goal in .25 cal.
I did not have good grouping with Kings or other pellets beyond 75yrds but I have not had the chance to test the JSB heavies out to 100yrds yet - so I don't know... it could also be my bbl or the idiot behind the trigger...
Casting 51gr BBTs is not that costly but they are much more costly than buying a few tins of JSB heavies...
I would only use the BBTs for 200 yrds targets or when hunting.
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It may very well be that in order to get heavy enough bullets to work in the more commonly available slower twists we may not be able to take advantage of the boattail.... That would be a shame, but it could, unfortunately, be reality.... We may be locked into draggy, flat-base bullets by the barrels that manufacturers choose to use.... Boatails may become toys for those few who can afford to replace barrels, or build PCPs, to match their capability.... :-\
It goes deeper than twist rate, of course.... The lack of standardization of bore diameter in airguns is atrocious.... PB's don't have a problem coming up with a standard, why should it be so difficult for airguns?.... The only reason I can think of is that the skirted diabolo pellet has made it so easy to get acceptable, close range accuracy with nearly any barrel.... The airgun manufacturers have become complacent, or is it the other way around?.... There were never consistent standards, so the pellet manufacturers have found a way to make (inflatable) pellet skirts that for the most part don't care what the bore diameter is.... A perfect example is how well the .300 cal JSB Exacts work in a .308 cal PB barrel, even though the head is nearly bore riding.... The skirt is large enough, and expands to seal, so all is good.... in a barrel that is 0.008" oversize.... ::)
It would be a shame if what could be a huge step forward in airgunning.... the ability to have a much lower drag projectile.... is passed over because the projectile has outstripped the barrels.... but I can see it happening.... It would be ironic that my attempt to modernize airgun projectiles, to keep up to the wonderful and powerful new PCPs we have, is defeated by their very inconsistency of design.... :(
match.... yes, the 41 gr. should be fine in all known airgun barrels for stability.... I think the GM barrel used in the MRods is 15.5" twist.... but I also think it is 0.254" groove.... like the LW.... BTW, a BBT in .25 cal at 1.5 cals. long, FN would be 46 gr.... It would be fine in an 18" twist, maybe still marginal in a 20"....
Bob
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I just recently upgraded the power of my .25 cal. Airforce airgun to where the 51 grain BBT will work. It has a 1-16" twist LW bbl. with .254" groove dia. Both bullet's driving band sizes fall outside of my needs of .253". If I can help it I do not want the additional step of resizing the .255's. Ideally the bullets would drop out at .2535", according to what I've read. Would it even be possible for me to resize the driving band of the .252" mould? And even if I could, would that work well, or not, in a .254" bbl.?
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My 0.250/0.252" 51 gr. BBTs drop at 0.2515" nose and 0.2535" driving band (+- 0.0002").... so I think they would be too small for a 0.254" groove.... The larger 0.253/0.255" will likely need sizing to work, but is probably the better choice.... NOE now have sizing bushings in airgun sizes (in 0.001" increments) so at least you don't need to order custom dies....
Bob
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Bob, thanks for reply. Ok, so I guess that I don't understand things as well as I thought that I did. I only ever cast bullets for a single action revolver, about 20 years ago. That was a 220 gr. Lee mould and all worked out perfectly, then. I read some posts of a semi-famous long-range airgunner, who cast 90 gr. bullets, in .257 cal, and it was he that suggested .001" less than groove diameter. I believe that he also said that .0005" under groove diameter was even better. The .25 cal. LW airgun dimensions, on the Georgia, USA manufacturers site, state .254" groove and .248" land diameter. I believe that Airforce uses German made LW barrels, I could be wrong. So your .250"/.252" mould is dropping .215" nose and .2535" driving band. What final dimensions should I be looking for for my own barrel?
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Most airgun guys that shoot bullets recommend 0.0005-0.001" over groove diameter for the best accuracy.... However, some like that much under.... others up to 0.002" over.... It ultimately will depend on your own barrel, and only trying it will confirm.... There is no point in trying to force a barrel to digest what it doesn't like.... You 0.254" groove barrel may like anything from 0.253-0.256"....
Bob
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I just recently upgraded the power of my .25 cal. Airforce airgun to where the 51 grain BBT will work. It has a 1-16" twist LW bbl. with .254" groove dia. Both bullet's driving band sizes fall outside of my needs of .253". If I can help it I do not want the additional step of resizing the .255's. Ideally the bullets would drop out at .2535", according to what I've read. Would it even be possible for me to resize the driving band of the .252" mould? And even if I could, would that work well, or not, in a .254" bbl.?
for now you might try knurling.. ;) choked L.W. down to ..? so running loose might help.. ;) alloy a touch hard and let the lands and grooves work... what is the land /groove bearing surface ratio and rifling depth...
I think that each barrel is a law unto itself you have to listen to it... the round as it is is not sacrosanct especially if you are trying to run a hybrid barrel...
I will be trying many experiments in trying to mill rounds with a Herters/Forster case trimmer/hand lathe... worked very well to hollowpoint 38/357...
heck to get thru the choke on an old 22lr barrel I am thinking may try paper patched... Beretta(I think strongly Hammer forged)
if I was to try the 50g in my stock .25 mrod...
would hollow the boat tail on some... hollow point and tail some... size under and knurl to help get it thru the choke... would getting cg forward help it pull itself thru the choke..?
may have to mill the tail some/off unless I up fpe...
point is you may have to really work at it to get it to work and still may get beat...
even if it its only accurate to 60 yards with less drift than a pellet you are still ahead...
the fpe/barrel mix is complex and a bunch of small changes can help suit the round to the barrel...
our forefathers used freshening sticks on their barrels... re-cut 25-20 to 32-20 with a cutter imbedded in a barrel lap of Nickel Babbit...
wildcatters developed rounds...
That's how you need to think to have a good chance of success...
But
you may get lucky and it is plug N play...
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Bob, thanks, again. Ok, I'll go with the .253"/.255" and see what happens.
K.O., what exactly does knurling accomplish? I've already removed the choke from this barrel.
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http://www.huntingnet.com/forum/black-powder/400904-knurling-bullets.html (http://www.huntingnet.com/forum/black-powder/400904-knurling-bullets.html)
https://www.google.com/search?q=knurling+cast+bullets+with+a+file&rlz=1C1GNAM_enUS688US688&oq=knurling+cast+bullets+with+a+file&aqs=chrome..69i57.29724j0j7&sourceid=chrome&ie=UTF-8#q=knurling+lead+bullets (https://www.google.com/search?q=knurling+cast+bullets+with+a+file&rlz=1C1GNAM_enUS688US688&oq=knurling+cast+bullets+with+a+file&aqs=chrome..69i57.29724j0j7&sourceid=chrome&ie=UTF-8#q=knurling+lead+bullets)
Basically
find bore and groove dimensions just past the leade and for muzzle if choked... try to size just below groove and knurl back to size for sealing and some of the lead will be smaller than the choke and some will be chamber sized... gives the lead somewhere to go and there is less friction...
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K.O., thanks a lot. Very interesting and that's something that I'll look into further.
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I'm sorry to bother, again, but I forgot to ask something. What bullet lube is best in this situation? Will Lee Liquid Alox work... or a special mixture of some sort?
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I don't use any lube....
Bob
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Thanks, Bob. Ok, I found the thread that I referred to in a post above, the semi-famous long range airgunner. I reread what he said about bullet/bore-size and I remembered it all wrong. Post #17 of that thread, after saying .001" over bore he uses the word "less." Maybe that's why I remembered it wrong or maybe I just remembered it wrong, I read it 7-months ago. Anyway, a 53/55 mould and accessories were shipped out to me, today. I'm looking forward to whole process and I hope that I can get this air rifle dialed in with that bullet. This evening I shot a 62.04 gr bullet over the chronograph and got 896.5 fps avg. for just over 110 fpe avg.
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Match
Based on my testing so far with hundreds of designs of bullets I start to get a feel of what works and what does not. Of course, mainly influenced by the guns I own or have access to. I believe these boattail designs only work when the bullet is long and heavy. The bullet you want me to try is even shorter than the one I already tried.
It is not just the BBT. Same thing when I swage a full length boattail - they are not stable. Bob could be right and you need a very fast twist rate to stabilize it. Problem with that is most guns do not have that and I make ammo for "most" guns not for a few custom guns. So if you need a 14 twist or faster to do so, I do not know of any barrels on production guns for .250-.252 with 10-14 twist rates so only a few guys who rebarrel or have customs guns could potentially buy it from me.
I hope I am wrong because no one wants this to work more than me, except maybe Bob :).
I never thought that I would be part of such a small subset. I chose the Warp so that I would be able to someday shoot these BBT in .25. I failed to anticipate that I would be a part of a minority of air gunners using TJ's liners. I would definitely buy from you. But I understand you are looking at not being able to get a return on your investment tooling up for this round.
What if we did a trial of these rounds in some of the Warps and Flexes in .25? My thinking being that there are a number of owners of these guns and that list is growing, the round was designed to function in those barrels and this micro niche of consumers might provide the demand necessary to get this round off of the ground. If the trial proves as effective as intended then you could do a survey here and possibly through the WAR website/ survey monkey and get a commitment from guys like me to purchase enough of the rounds to make it worthwhile.
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Scotty do you know the twist rate of the barrel? I have tried to find it but I can not seem to locate it. I have shot these out of 1:17.7 twist and close in were fine but at range were unstable. I did shoot one small group that looked good but could not repeat it, not even close.
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Checking...
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The TJ's .25 ACP liner is 14" twist.... Both the NOE and LBT 51 gr. BBTs are stable in it.... What I would really like to know is how they work in a GM barrel in an MRod, they are 15.5" twist....
Bob
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Naturally, Bob beat me to the punch before I could find my link to quote the man himself. But here is the link anyway.
http://www.gatewaytoairguns.org/GTA/index.php?topic=58933.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=58933.0)
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That is the link to the previous LBT design, the NOE one is slightly different.... It has a larger Meplat at 70%, and the mid body is just under land diameter instead of a classic lube groove.... and it will fit in a Hatsan magazine, the LBT bullet was too long.... They seem to shoot about the same, from my limited experience....
Bob
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Absolutely. I also really like the appearance or shape of the revised round. I find it more appealing, not that that makes any difference. For some reason I find this round and the .257 BBT to be more astheticly pleasing than other rounds. I dunno, guess I have issues :o
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Bob - does somebody have groups posted with this bullet?
Does anyone know if any other manufacture uses this barrel or at least this twist rate. I know 1:17.7 is very common, note sure about 1:14.
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Shot group: http://www.gatewaytoairguns.org/GTA/index.php?topic=69114.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=69114.0)
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That's an older version, not the new and improved but I suspect that it will be very suggestive of the rounds capability.
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I won't be able to shoot for 3 maybe four weeks, WAR permitting, but I'd be happy to pay for some test rounds to try in my Warp and post results. Anything I can do, let me know.
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Strangely no, I haven't seen any groups posted.... I was shooting (the only time I got out) to measure the BC, and was getting about an inch at 50 yards, with no tuning or fiddling with velocity, just sized to 0.250".... LW barrels are 17.7" twist, and the GM barrel is 15.5".... I don't know of any production airguns that use anything faster than that....
I was trying to optimize the ballistics, and have it fit the Hatsan and MRod magazines, and work in a GM (MRod) barrel.... In hindsight, shortening the boattail (so it has a larger base), which would also shorten the overall length slightly (and the weight, of course) might have made it work better in the LW twist.... It is possible that machining a small amount off the base of the mould to do that could make a huge difference.... My calculations show that removing 0.040" from the back of the bullet would easily allow it to work in an 18" twist.... creating a bullet in between this 51 gr. and the 41 gr. BBT soon to be made by NOE.... Even removing 0.020-0.030" from the back may be enough....
Bob
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Scotty do you know the twist rate of the barrel? I have tried to find it but I can not seem to locate it. I have shot these out of 1:17.7 twist and close in were fine but at range were unstable. I did shoot one small group that looked good but could not repeat it, not even close.
Hi Nick First Very RESPECT-fully I disagree about the 41g round it is not a boat tail it to me... is functionally very closely related to a rebated Kieth semi-wadcutter and its performance characteristics/envelope will be very close... guess what in my 38/357 that sort of round did very well at lower velocity...JMHO...
and they worked very well with small hand cut hollow points too... rested Ruger Blackhawk 6" barrel stock sights 1.5"-2" groups normal at 50 yards... I think a better shot could have done better... but yep do not try and +P them.. ;)
http://www.midwayusa.com/product/214652/oregon-trail-laser-cast-bullets-38-caliber-358-diameter-158-grain-lead-semi-wadcutter-box-of-500 (http://www.midwayusa.com/product/214652/oregon-trail-laser-cast-bullets-38-caliber-358-diameter-158-grain-lead-semi-wadcutter-box-of-500)
http://www.midwayusa.com/product/150058/oregon-trail-laser-cast-bullets-44-caliber-431-diameter-240-grain-lead-semi-wadcutter-box-of-500 (http://www.midwayusa.com/product/150058/oregon-trail-laser-cast-bullets-44-caliber-431-diameter-240-grain-lead-semi-wadcutter-box-of-500)
I am a touch worried about the bearing length and maybe a 44g-45g with a longer body would be better but I think keeping it short may just help get it thru the choke...(By the way I am tired of hearing you can't shoot cast in a choked barrel... can, been done a lot in small bore just some may not work)...
so yep all the above is just my opinion... but why I chose the 41g to start from... not to mention I want to keep fpe down to 70 and below... would really have to mod the 51g for 50-60 fpe... and while it would be fun to try... the 40g was it for me...
I would love to have bought some of your swaged bullets and the 50g BBT .250 from you (to try and carve into what my barrel likes) but alas was not able with my budget... And the budget just got set back my faithful old Bud Pugsly (large grey Manx) needed put down... and the faithful old wash machine passed away (it was comical how it happend tho)... but about 600 in emergency expense...
I was looking at the Kalbre site and it says the .25 barrel is L.W. ..? I thought they where Hammer forged CZ...? if L.W.(softer barrel) with heavy slow sounds like a harmonic prob waiting to happen... so shortening the nose( to a ~ .75 meplat (~.1875))) or tail or both might help for that barrel... by getting velocity up and lessening spin needed... ?
I think there are a lot of things that can be thought about and tried for the many barrel types and will require a good amount of flexibility to solve issues that arise when shooting cast with air through those barrels...
One such thought is that with some rifling types the mid and long BBT may need to be just a touch hard cast because of the small bearing area...
This is a separate from business because as a business yep it is important to sell round proven to work in the more common barrels...but at least you can deduct development expenses(I think)...
I am going to enjoy the processes of trying to develop the rounds for different barrels... just two .25 for me (for now) choked Benji and non choked Crosman...
Now in the .22-.224 range well I have lots of challenges planned I figure about 3-5 years worth of experiments to test my theories and what I think I know about matching fpe/rifling type/barrel type/twist to each round and type of round...
we are the modern wildcatters and that is why I want to go small bore cast with air... for the challenge of it...
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I am sorry I don't understand what you disagree about. You quoted me asking about a twist rate and a statement of me shooting a bullet. What exactly do you disagree about.
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Sorry
concentration probs wrong quote... :-[
it was about the 41g BBT
" I believe these boattail designs only work when the bullet is long and heavy. The bullet you want me to try is even shorter than the one I already tried."
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oh those where not the exact rounds used what my bud loaded for me was a Bevel base Semi-wadcutter just about like it...I do not remember the alloy but here are some that I think were about what I was sending down range(alloy wise)...
http://www.midwayusa.com/product/174065/meister-hard-cast-bullets-38-caliber-357-diameter-158-grain-lead-semi-wadcutter-box-of-500 (http://www.midwayusa.com/product/174065/meister-hard-cast-bullets-38-caliber-357-diameter-158-grain-lead-semi-wadcutter-box-of-500)
http://www.midwayusa.com/product/2046539567/hunters-supply-hard-cast-bullets-38-caliber-357-diameter-158-grain-lead-semi-wadcutter (http://www.midwayusa.com/product/2046539567/hunters-supply-hard-cast-bullets-38-caliber-357-diameter-158-grain-lead-semi-wadcutter)
point is that in the old days they would argue over which had better accuracy the bevel base or flat base SWC... well mine preferred bevel for some reason...
But in most guns I think they are pretty equal... below is a good read for those thinking of getting into cast and it states in the wadcutter section testing said about the same... just can not load the bevels hot...
I really do see the 41g BBT almost as a new type of SWC more than a boat tail... and I do think that the rebate is a slight improvement over the bevel base...
my personal opinion is the rounder nose will self correct slightly better than the SWC conical nose and the rebated base will have some drag benefit but mainly give a clean base.... the rebate can help stability(less tail wag) out of the barrel...over both flat and bevel base...
so yes I tend to have a bit of faith in the design... and know it is not a long range design... but am hoping for 75 yard+ moa on a good day as my goal at 55-65 fpe...
http://www.lasc.us/Fryxell_Book_Contents.htm (http://www.lasc.us/Fryxell_Book_Contents.htm)
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Send me some bob I'll try em out in my Mrod. ;D
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I think you would need the larger diameter.... 0.253/0.255".... pretty sure the GM barrel is 0.254" groove.... I only have the 0.250/0.252" 51 gr. at the moment....
Bob
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Bob I checked my digital caliper against a 3/16 drill bit and got .1875... but do not have a pin gauge to check...
any ways using Benji 27g I keep getting .2525 groove and .2505-.251 bore at the breech and 2495 groove at muzzle...
need some #3 buck to do it better not to mention maybe a good blade mic... but I do not think I am much off... multiple 1/4 drill bits nor the part of my 30 cal jag that measured exactly .250 will enter the muzzle...
I have not tried to measure the new Synrod .25 barrel yet(will soon)... wish other could check theirs... so I ordered the 41g .252 mold hope it drops a touch large like most molds.. ;)
just a small chance it could do well unsized...
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WOW, only 0.001" deep rifling?.... I'm shocked.... :o
Bob
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WOW, only 0.001" deep rifling?.... I'm shocked.... :o
Bob
well Bob honestly I am not these are pellet barrels... ;) if you look at a (button rifling) Remington 513 Targetmaster they are only about .0015 tall...the(cut rifling) Shultz & Larson M30 target barrel I just bought is about .0013... The (hammer forged) Beretta Hakim is a strong .0015 all with the same narrow .03 land width and six lands and grooves...
what they have in common is they are all meant for target... Pope style thinkin don't mess up the round any more than you have to...
When my Dad let me start shooting his Remmy 512 without supervision first thing he told me was if I used any High velocity rounds it would be the last time...
Point is they are not meant for high velocity/fpe... accuracy usually would not so good anyways...~ 80 fpe very good- about 120 fpe nope
I really wish people would look at their barrels rifling before sending lead down range... just looking at the rifle well this guy should have know to stick to TARGET ammo... >:(
https://www.youtube.com/watch?v=dF5x6JUCrZM (https://www.youtube.com/watch?v=dF5x6JUCrZM)
(an aside in the below link are the machines that made that barrel... ;) and mine) mechanically Lapped with a Tin lapp.. 8)turn cc on and skip to about about 50 second in...
https://www.youtube.com/watch?v=Hecf_z0lFWQ (https://www.youtube.com/watch?v=Hecf_z0lFWQ)
well anyways back on topic...if you are designing for low fpe 2260/Disco .22 you can get away with almost GHOST rifling and it can be a good thing... if you have the land/groove bearing surface ratio about right...
as you go up in fpe the more "grip" needed to keep it from stripping... but surprisingly little is needed at 80 or so fpe... the Mrod is designed for about 50 fpe Max...
A bunch of folk put down the Crosman barrels but if you look there is method to their madness...
And with all that said it is why I think for the Mrod .25 Barrel Carefully milling the 51g BBT down to about 44g with a cupped/hollow base and hollow point might be the ticket... or just trim the nose and tail but I want to keep the round as cast length myself...just think it would be better...
point is just how far can you push the Mrod Barrel 80-100-120 fpe? will casting slighty harder help as fpe goes up..? but then you have a slight choke..? Knurling..? sizing will be very important for the higher fpe...
All just my thoughts... cause in the end air power is not powder there is stuff to discover... ;)...
I know I have posted rifling picks(Hakim 22lr ,2260 ,L.W. .22 pellet ,Marlin MG .22 wmr) in other threads here are the Mrod .25 NPXL 725 and S&L .22lr
... ??? ::)
Thoughts..?
Look in a 2260/Disco barrel and heck I am not even sure they know if its at .0005 or .00075 or.0009 ... I will as one of my experiment sleeve one to .5 and see if I can mod a .217 BBT to about 24g-26g to see how fast it will handle with its very light rifling...Betting it will be about like a CB cap... ;)
8/14 *added L.W barrel muzzle pics...
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the reason I keep talking about lightening the rounds is because for the most part no matter the weight/lenth of the round I want my velocity to be in the 800-950 fps range... and a longer light round is one of the things I want to explore
along with weight forward hollow base and how they react to being under/over-spun in terms of accuracy at different ranges.. such so forth and on...
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If anyone gets these sized right for the GM Mrod barrel I would REALY like to try them out. I'll pay for em just let me know. Thanks!
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If anyone gets these sized right for the GM Mrod barrel I would REALY like to try them out. I'll pay for em just let me know. Thanks!
Have you tuned your Mrod up in fpe any... Mine is at 50 fpe stock, 1% es for 9 shots... point is with a 50g projectile in the short 19" barrel, velocity will likely be down in the low 600s or so...
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It's getting up to 820fps with 43.2 EJ's. Flush hammer striker, Hogged valve light poppit spring and .187 ports. Hopefully more with the bolt mod on its way. I'm thinking about some rat snipers to test also.
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well that is about 65 fpe and about the bare min needed...it would not show of the best side of the round but could work... about 750 fps or so...
just the barrel being .5" could cause harmonic probs with no further velocity to try and catch a sweet spot with..?
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That's what barrel tuners are for.... tuning the barrel for your velocity instead of vice-versa....
Bob
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That's what barrel tuners are for.... tuning the barrel for your velocity instead of vice-versa....
Bob
Well Sensei yes and no... imo... with the thinner barrels it just sometimes does not work... me I honestly feel they are better at fine tuning the sweet spot than gross corrections of not being close to one...
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I received my FN mould today. I only cast 8 bullets, was trying to hurry so I could chronograph them in the failing light. Only 4 filled perfectly. I shot 3 over chronograph, but the valve stem broke on the first shot. I shot this gun every evening for the last week or so. I even killed a 15 lb. woodchuck last evening with it, but when I put one of Rsterne's creations in my gun it broke it. What kind of omen is that?... LOL. Anyway, the driving band measures .2571", so I'm going to have to buy the universal die and sizing stuff, from NOE. The one bullet that I weighed is 51.52 grains. I'm going to modify the mould to have two HP pins. I wanted full control of pin diameter and shape, that's why I went with the FN. I'll update as I proceed.
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Thanks for the update. :D sorry about the stem.. :(
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OWEN?.... OMEN?.... am I the only one who noticed that all you need to do is flip the W over to get an M ?
Sorry, I couldn't resist.... *grin*....
Bob
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The TJ's .25 ACP liner is 14" twist.... Both the NOE and LBT 51 gr. BBTs are stable in it.... What I would really like to know is how they work in a GM barrel in an MRod, they are 15.5" twist....
Bob
Dairyboy who has a .25 WAR emailed Jim about the barrel. It is a TJ liner with 1:22, .250/.243. I believe that was Mike's barrel he had them make.
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You are correct, Mike (CarsonRatSniper) had TJ's make a 22" twist barrel, primarily for pellets.... Until that was made, the only .250 cal barrel available from TJ's was the .25 ACP barrel, which is 0.250/0.243 with a 14" twist.... Those are the only ones I have used.... I don't know what W.A.R. uses for their .25 cal barrel....
Bob
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According to WAR (from Dairyboy), Jim Gaska emailed him that the barrel they are using a 1:22 twist rate from TJ .250/.243.
Based on what I read this bullet will not work in this barrel.
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That is likely correct.... The 41 gr. should be fine, although it is designed for a 20" twist.... It is at Last Call at the present time, and is available in either 0.250/0.252" or 0.253/0.255"....
http://noebulletmolds.com/smf/index.php/topic,1319.0.html (http://noebulletmolds.com/smf/index.php/topic,1319.0.html)
Bob
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well that is about 65 fpe and about the bare min needed...it would not show of the best side of the round but could work... about 750 fps or so...
just the barrel being .5" could cause harmonic probs with no further velocity to try and catch a sweet spot with..?
With the modified bolt it is now getting 885fps avg up to 75ft lbs is that better? ;)
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well that is about 65 fpe and about the bare min needed...it would not show of the best side of the round but could work... about 750 fps or so...
just the barrel being .5" could cause harmonic probs with no further velocity to try and catch a sweet spot with..?
With the modified bolt it is now getting 885fps avg up to 75ft lbs is that better? ;)
It certainly buys you a little bit of flexibility fps wise... For me reaching about 800-850 fps with this round would get me to buy the mold... and will probably happen in a while... You need to slug your barrel to find out what you have for bore and groove...
But you are still probably best served by the 40g .25 BBT ...
the 40g .25 BBT well fpe wise in my mind will allow turning up and down to see about finding a sweet spot... hopefully would work great from 800 fps on up to 950 or so... then you could turn down fpe for jus' plinkin'...
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I cast 528 of the 51 FNs. I don't have the resizing stuff yet, but now I'm ready for when it arrives. I modified a stock valve stem and could only get it to shoot 31.02 gr H&N Grizzly pellets to 1089 fps. The homemade valve stem, which broke, was propelling these 31.02 gr pellets to 1123 fps, and it wasn't nearly turned up all the way. The gun is now turned up all the way and is only getting 1089 fps. So I'll have to make another like the one that broke, but not drilled as deeply, etc. So anyway, I put one of these 51 gr FNs (51.52 gr) over the chronograph and got 965.6 fps for 106.69 fpe. If I get the same improvement as Bob did, from resizing, then that could add 20 fps. And an improved valve stem might add another 20 fps, so it's possible that I'll get these to shoot around 1000 fps or so before I'm through. By the way, my barrel length is presently 16.25", 18" Airforce barrel with 1.75" removed (chokeless, now.) So far I haven't shot these at a target. I don't really see the point until they're sized, but I may try it anyway, just to see what happens.
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Before shooting at the 50 yard target, I took an empty screw on top pellet tin, wiped it out, added 2-drops of Motorcraft 5W-20 synthetic motor oil, then added approx. 50 of the 51 FNs, closed the lid and spent 3-4 minutes swirling this around until a very thin even coating was achieved. The first 3-shot group was a perfect triangle with 3/4" between each hole. That group shot 2.5" low, 1.25" left of where the gun was sighted in for H&N Grizzlies at 1100 fps avg. I made the turret corrections and shot another 3/4" group that covered the center dot of the target, but was .25" too far right. Amazing! I didn't even want to shoot these unsized as Bob had stated earlier in this thread that his resized bullet groups were "about 1"." He was probably shooting 5-shot groups though. I shoot 3-shot groups because yesterday I chronographed 3 Grizzly pellets in a row which gave 1085, 1089, 1085 fps. I've not changed any power setting since then. I haven't chronographed 3 of the 51 FNs in a row, yet, but I believe that they're very close also, based on the group size. For now, I can continue my war with the woodchucks just fine with this kind of accuracy, 1.363 moa. I'm really hoping that resizing will get me into sub moa territory though.
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Sounds like you've already got a great combination....
Bob
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Well it seems Owens Omen turned out to be that your rifle was "Owen" you some good groups in return for you attentions.. ;)
sorry could not resist.. ::)
1.3 moa first groups at 50 yards... That is very encouraging...sub moa at 50 seems very possible and it seems 1:16 is enough twist with a L.W. barrel...
Hey did you chuck the cut off part of the Barrel... I could send a few bucks to mail it...want to take some pics to compare to the MRod and Trail XL rifling (and any other I can get hold of also)... according to specs it is way taller... also I want to measure/aproximate land width I have .22 and .177 L.W. ...
Like I was talking about early in the thread it just may work to semi/bore ride the nose if there is enough land width to let it ride the "rails"... just might be worth trying imo...
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seems 1:16 is enough twist with a L.W. barrel
Sorry, where did I miss that the LW barrel Owen has is a 16" twist?.... LW barrels are usually 17.7" twist.... Not saying it isn't 16", just I've never heard of one....
Bob
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I just recently upgraded the power of my .25 cal. Airforce airgun to where the 51 grain BBT will work. It has a 1-16" twist LW bbl. with .254" groove dia. Both bullet's driving band sizes fall outside of my needs of .253". If I can help it I do not want the additional step of resizing the .255's. Ideally the bullets would drop out at .2535", according to what I've read. Would it even be possible for me to resize the driving band of the .252" mould? And even if I could, would that work well, or not, in a .254" bbl.?
and at pyramyd
https://www.pyramydair.com/product/airforce-condor-ss-pcp-air-rifle-spin-loc-tank?m=3063 (https://www.pyramydair.com/product/airforce-condor-ss-pcp-air-rifle-spin-loc-tank?m=3063)
I wish that all descriptions included twist rates... I think my trail XL 725 barrel is around 1:18.5 but that was a very rough measurement...
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Interesting, AirForce must be getting a custom barrel made for them by LW.... Thanks for that information.... With the success of the 51 gr. BBT in the 16" twist, and the marginal performance that Nick found in the 17.7" at just under 800 fps, I guess we pretty much have an answer for "how fast do you need to spin 'em?".... It will depend on the muzzle velocity, and the 17.7" may well work if you keep that lower (in the mid 700s or below?).... but for high powered PCPs the 16" twist appears to be the minimum.... at least based on current data....
Bob
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Bob if I get a chance to shoot with someone with a different gun/barrel I will try to see how they do. I wish they worked in the 17.7 but they are not far from working in that barrel, I did get one good group but could not repeat.
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By any chance, Nick, was the one group that was good, shot at a slightly lower velocity?.... Stability in the subsonic region decreases as velocity increases, that could explain your results with the 17.7" twist barrel.... Even if the velocity was the same, even just a change in air density might tip it one way or the other, if it was right on the edge.... I can remember stories of benchrest guys having problems at high altitude, or different atmospheric conditions, in the days where they were pushing the stability factors down to 1.1 or 1.2.... Current thinking is to stay as close as possible to SF = 1.5.... Just a thought....
If they are THAT close to working in a 17.7" twist, just a few thou off the base of the mould blocks to shorten the bullet and enlarge the base diameter (both of which increase stability) would do the trick.... Here is a drawing of the NOE 51 gr. that has been shortened 0.027" at the back....
(http://i378.photobucket.com/albums/oo221/rsterne/NOE%20Bobs%20Boattails/NOE%20250%20cal%2048%20gr_zps4xl5luqz.jpg) (http://s378.photobucket.com/user/rsterne/media/NOE%20Bobs%20Boattails/NOE%20250%20cal%2048%20gr_zps4xl5luqz.jpg.html)
The boattail and base diameter are the same as the 41 gr. BBT.... The change, at least in theory, make the 48 gr. bullet shown above as stable in an 18" twist as the 51 gr. is in a 16" twist.... It should be a simple thing to mill of the base of an existing 51 gr. mould to make this change so that it would work in an 18" twist.... You may not even need to go this far, just 0.010-0.015" might do the trick.... but only testing would tell you for sure....
Bob
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Well elevation could be a factor I shot a group in Colorado that was great at 50 yards, elevation 5k feet I think.
The second attempt that was not good was around 2500 feet but out of same gun which was a regulated cricket. Cricket shoots jsb 25 grain around 975 or so.
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well Bob he also cut off the choke which probably made it a bit easier...
Also I know it goes against the math but I feel each different round design there is a minimum rpm it likes... so getting the fps up a bit to 805+ fps MIGHT help in the 17.7 twist...
Deadguy is not reporting any keyholing at about 725 fps in a 1:16 L.W. (choked?) that gives about 32,600 rpm...
1:17.7 at 780 fps is about 1000 rpm slower (31,700)... but add about 30 fps (810) and that gives about 32,900 rpm...
this is just the sort of situation I want to experiment with moving the CoG forwards by hollowing the base as much as the psi will allow... dished ,cupped and maybe drilled about .1 about .3 deep after cupping... would also allow maybe just enough weight loss to hit closer to 800 fps...
But yep just chopping the tail a bit would be much easier.. ;)
Chokes well depends on harmonics because if it allready is having that sort of trouble 50g slamming into the choke adds a whole magnatude to the unpredictability... that a larger/stiffer/shorter... less active choked barrel will not face...
Then also probably have to watch for leading at the choke...
?
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Running the dimensions of the 51 gr. BBT through the Kolbe Twist Calculator, using a 17.7" twist, at 800 fps at 5000 ft. the Stability Factor is about 1.7.... while at 2500 ft. it drops to about 1.55.... and at sea level it drops further to about 1.45 (all at 59*F, normal barometric pressure).... These are extrapolated (guessed) numbers, because I have to estimate where 800 fps is, between the lines on the chart at 500 and 1000.... Regardless of the actual numbers, the bullet is about 10% more stable at 5000' than at 2500'.... That could explain your results.... FYI, in a 20" twist, at sea level, at 800 fps the SF is only about 1.1....
Bob
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Kirby, rpm isn't everything, because a bullet is the least stable right at Mach 1, by a huge margin.... Look at the charts on page 3, in post #43 and you will see what I mean.... The rpm increases with velocity, but the stability still drops in the subsonic region....
Bob
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Bob of course it is not everything but in some cases the added rpm from the added velocity may let you run bit a slower twist especially if it is right on the edge like this situation...
yes that 30 fps may change the drag profile on the nose to much for it to matter... but I have a bit of faith in the round flat nose up to the mid trans sonic region not changing much with that 30 fps change... and the bit of boost to the gyroscopic stability just may be enough.. ::)
Probably in the higher trans sonic the less likely it is to help...
Bunch of maybes I know but this subsonic boolit stuff out of air rifles is breaking new ground...
I did look to see if I could find a link that refers to this and though it is at very high velocity it is alluded to in this link...
scroll down to
"Implications for Gun Builders and Reloaders"
http://bulletin.accurateshooter.com/2008/06/calculating-bullet-rpm-spin-rates-and-stability/ (http://bulletin.accurateshooter.com/2008/06/calculating-bullet-rpm-spin-rates-and-stability/)
I know in years past I have talked with others that have the same thought but it was a good while ago...
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Kirby, I'm sure that I have that piece in the scrap bucket. When/if I find it then I'll PM you. I already believe that when sized these bullets will shoot 1 moa or better, but I'll have to wait and see.
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If you look at those graphs in the post I mentioned, you will note that when Supersonic, you can use a slower twist the faster you go, because increasing the velocity increases the rpm and stability.... This is the region where what you are talking about (increasing the rpm) works.... However, when Subsonic, the reverse occurs.... as you increase the velocity, the stability decreases, even though you are increasing the rpm.... The overturning forces increase faster than the rpm when you are below Mach 1.... hence trying to get more stabillty by increasing the velocity is the wrong way to go when Subsonic....
Bob
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Here are a pair of 51 gr. BBTs recovered from soap after impacting at 100 FPE.... The upper bullet is a FN, and the lower one is a HP....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Front%20and%20Back_zpsi21tephi.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Front%20and%20Back_zpsi21tephi.jpg.html)
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Side%20and%20Front_zpsejc5kmlc.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Side%20and%20Front_zpsejc5kmlc.jpg.html)
It is quite obvious that the boattail portion never contacted the rifling, it looks like it did when it came out of the mould.... Those are from a TJ's 14" twist barrel....
Bob
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What rifle are you hiding thats pushing 100fpe? :o
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My Disco Double.... I have three 25" barrels for it, .250 cal 14" twist, .300 cal 26" twist, and .357 cal 26" twist....
(http://i378.photobucket.com/albums/oo221/rsterne/30%20cal%20Disco%20Double/IMG_3527_zpsc4058736.jpg) (http://s378.photobucket.com/user/rsterne/media/30%20cal%20Disco%20Double/IMG_3527_zpsc4058736.jpg.html)
Here are the best tunes with pellets and bullets in each caliber.... 4% ES strings from a 3000 psi fill....
(http://i378.photobucket.com/albums/oo221/rsterne/30%20cal%20Disco%20Double/DiscoDoubleTunes_zpsef65df88.jpg) (http://s378.photobucket.com/user/rsterne/media/30%20cal%20Disco%20Double/DiscoDoubleTunes_zpsef65df88.jpg.html)
If I crank it up in .25 cal, tethered at 2900 psi, here is what it is capable of....
(http://i378.photobucket.com/albums/oo221/rsterne/30%20cal%20Disco%20Double/Disco%20Double%2025%20cal%20Preloads_zps2zka51dp.jpg) (http://s378.photobucket.com/user/rsterne/media/30%20cal%20Disco%20Double/Disco%20Double%2025%20cal%20Preloads_zps2zka51dp.jpg.html)
The highest I have obtained with it, in .357 cal, is 192 FPE with 132 gr. bullets....
Bob
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That thing is sexy! Got to get me one of them CF shrouds on my Mrod.
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It's actually not a functional shroud.... It is in compression, and the barrel is in tension to stiffen it.... LDCs are illegal in Canada....
Bob
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If you look at those graphs in the post I mentioned, you will note that when Supersonic, you can use a slower twist the faster you go, because increasing the velocity increases the rpm and stability.... This is the region where what you are talking about (increasing the rpm) works.... However, when Subsonic, the reverse occurs.... as you increase the velocity, the stability decreases, even though you are increasing the rpm.... The overturning forces increase faster than the rpm when you are below Mach 1.... hence trying to get more stabillty by increasing the velocity is the wrong way to go when Subsonic....
Bob
Bob if it did not have a relatively short nose and a 70% meplat it would be very true... My thinking is that the shorter the lever(CoG/CoP) the less that is true... the longer and the pointier the more twitchy...
also I think on the pointy bullet the faster you push in subsonic into trans sonic the further forward the CoP moves... with a 70% meplat not so much until higher into the trans sonic...
Point is I do think it can gain a bit of stability because the CoP is more static as it punches thru the air rather than cutting thru with a Knife edge...
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Believe what you want.... I'll follow the advice of Robert McCoy.... Those graphs are specifically for the 51 gr. BBT, calculated using his program, developed at the Aberdeen Proving Grounds.... If he says the stability when Subsonic decreases with increasing velocity, I believe him as to the trend.... How the actual SF number relates to the twist required may be up for debate, but IMO not the general principles.... You will find that general shape of graph for every projectile, complete with the discontinuity at Mach 1....
Bob
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Bob, What shell holder will I need to get in order to use NOE's ram, for the sizing operation? This is for a Lee Hand Press.
Here's an image of the first three shots, with the NOE/Rsterne 51 FN bullets, at my 121 yard target:
(http://i38.photobucket.com/albums/e127/kameradrei/_1020813_zpsffg1mxnl.jpg)
I then decided to clean the barrel and shot another three shot group at the 50 yard target. It measured approx. .593"
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Believe what you want.... I'll follow the advice of Robert McCoy.... Those graphs are specifically for the 51 gr. BBT, calculated using his program, developed at the Aberdeen Proving Grounds.... If he says the stability when Subsonic decreases with increasing velocity, I believe him as to the trend.... How the actual SF number relates to the twist required may be up for debate, but IMO not the general principles.... You will find that general shape of graph for every projectile, complete with the discontinuity at Mach 1....
Bob
Bob with respect I will use your own words against you... but I had come to the conclusion on my own a while back after seeing the shadowgraphs in Mr Mccoys paper on .22lr ( BLR-MR-3877 ) and reading Robt Rinker, 'Understanding Firearm Ballistics, Basic To Advanced Ballistics Simplified & Explained,' wish I still had it can only hold on to general ideas now (brain probs)
anyways with humility cause it is easy to be wrong but I do think this design accomplishes exactly what you describe... how is up for debate...
"As an airgunner, I deal in subsonic flight almost exclusively.... I think you will find that for most bullet shapes the minimum stability occurs at a couple of fps under the speed of sound.... The exception is a cylinder (flying ashcan) where the stability continues to drop as the velocity decreases.... Bullets with a very short nose and wide meplat can have a nearly constant stability at nearly all speeds subsonic, but you virtually have to design a bullet to act that way...."
from http://castboolits.gunloads.com/archive/index.php/t-209192.html (http://castboolits.gunloads.com/archive/index.php/t-209192.html)
remember our discussion of true hemi spherical vs flat nose or semi hemi pellets and that about 600 fps is the place where the wadcutters flow changes... sort of the same deal...
but way more complicated...
I really wish my brain worked better than it does now so I could present my thoughts in this discussion better... ;)
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Owen "Hot Dog" pretty much MOA at 50 and not so bad at at 121 unsized...
It is hard to tell but it does look like just a bit of yaw at 120... might go away (if it is even there pics can deceive) when the barrel is not doing the sizing...
Makes me want to steroid my Mrod now instead of later.. ;)
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Kirby, yep, the part you put in bold pretty much sums it up.... but that doesn't describe the 51 gr. BBT.... One look at the stability curves shows you that.... Did you by any chance look at the date of that post?.... I hope I have learned a little in the last 3 years.... I only started on the BBT quest a couple of years ago.... it just seems longer.... ::)
Until I find a better tool, I will continue to use Kolbe's Twist Calculator, which uses Robert McCoy's program to do the calculations.... All my BBTs, including the really short ones, show less stability as you increase the velocity in the subsonic range, according to those calculations.... I will continue to believe that is correct until somebody proves otherwise, it just seems the prudent thing to do....
Owen, there is no separate shell holder in my Lee press, the NOE rams fit right into the Lee holder.... I am still using my Lee rams.... I use a Lee bench press, but it should be the same?....
Bob
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Thank you, Bob. I haven't had it out it's box since 1998. I'll look into it, now.
Kirby, thank you for your input about the yaw. I don't know, yet. That target is a used UnitedStates Priority Postal mailing box that has sat at 121 yards for the last couple of months. The wind blows it over often. It rained on it the night before I shot that 3-shot, 2.196" group. The box wasn't perfectly square with my shooting position either. That 2-shots landed in the 1.375" circle was quite pleasing as I had only zeroed the gun at 50 yards. My phone app., Strelok Pro, told me where to hold at 121 yrds. and these are the very first 3-shots that I took at that target. I could be wrong, but I'm expecting great things after sizing.
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"it just seems the prudent thing to do...." I tend to agree that any thing about how it builds the stagnation zone thru what speeds is conjecture and also tend agree about the general trend;
but can there be a period where the round sort of goes to sleep..? ::)
with today's tech I wonder if we could observe the building /shape of the stagnation zone at differing fps... and actually see physical drag profile that would tell a lot...
How did you jigger the program for the rebated boat tail..? just use a steeper angle??? or just go by length and base diam... neither seems quite right..?
oh and in my defense Eley Tenex is sold as the nose being the reason for extra stability and I drank the cool-aid...
here are the clean versions of some of the pics in memo BRL-MR-3877
http://www.network54.com/Forum/79537/thread/1268775273/Changes+in+BC+with+velocity%85%85.continued (http://www.network54.com/Forum/79537/thread/1268775273/Changes+in+BC+with+velocity%85%85.continued)
"
The iconic flat nose projectile of ELEY tenex is one of many innovations pioneered by ELEY engineers. As it cuts through the air its revolutionary design pulls the centre of pressure forwards, aerodynamically stabilizing the projectile and increasing accuracy at the target.
"
from
http://www.eley.co.uk/eley-tenex (http://www.eley.co.uk/eley-tenex)
??? ::) ? ;)
Owen did you polish the barrel or does it just have some rounds thru it...
I need to take some measurement but it looks like the rifling is just a bit taller than the Benji rifling...other than that I think I get about .2495 groove for the choke... looks a lot like the Benji/ Green mountain and NPXL rifling.... will ad muzzle pic of the cut off you sent to post #79
I was thinking about fpe and such being close to .22 target and thought...
in very good indoor conditions .22lr and a high bar but should be... so yep pulling off sub moa does look very possible...
http://www.accurateshooter.com/guns-of-week/22lr-rimfire-ammo-comparison-test/ (http://www.accurateshooter.com/guns-of-week/22lr-rimfire-ammo-comparison-test/)
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"Owen did you polish the barrel or does it just have some rounds thru it..."
If you're asking about the choke... neither. I cut the choke off before I ever fired a single shot through the brand-new barrel. I have polished the bore of the remaining 16.25" of barrel, though.
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I found a post a few pages back interesting concerning the AirForce .25 barrel as the following quote is direct from Rachel Gonzales at AirForce when I ask if the LW barrel listed on LW's site is the same as the Airforce LW barrel. AirForce's replied specs do not agree with the specifications posted a few pages back:
"Hi Mr. Moore,
Our .25cal barrel measures .248 land and .255 groove. Just about the same.
Twist rate 1:17.22. Have a good day!"
The reply from AF was on 25 March 2016
Thurmond
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well I wish she would post that here and explain how a major re-seller post incorrect specs without them correcting the twist rate?
as for the bore /groove specs that might be just past chamber groove and bore at the choke the lands are not that tall .007... looks more like .0025+ to me... but hard to tell without a good blade mic.. maybe .004
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Well Owen just trying to figure out these things even to the naked eye the rifling seems sharper and the barrel smoother on the L.W. and it makes me wonder about the machinability of the alloy of each...the L.W. could be smoother because it is a touch softer(sulfer?)... at the price point of each I wonder how long each button is considered to be in spec...
wish that some reliable test would let us know more about the alloys of each...
can pretty much tell the L.W. is a swaged choke...
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"Our .25cal barrel measures .248 land and .255 groove. Just about the same.
Twist rate 1:17.22. Have a good day!"
Ok, I'll go slug my barrel and let you know what I find. I hope that this is a newly implemented specification and that my barrel is not like this, though.
Kirby, yes the LW barrel is softer than some others that I've lapped. I had one chinese, Crosman barrel that was softer, but another Chinese, Crosman barrel that was harder. A Turkish, Hatsan, barrel was the hardest that I've seen, so far. If what "Tritium" is saying is true then I'll probably be looking into buying the 1-16" Green Mountain barrel, so that I can use this mould and all of the resizing components that I purchased. We'll see soon.
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Unfortunately what "Tritium" has shown us about the Airforce barrel's ROT and bore dia. is true. My barrel mics exactly .255" dia. and the ROT is really close, if not exactly, 1 turn in 17.22 inches. I have never once doubted the advertised 1-16" ROT of twist that Pyramyd-Air, and others, have touted the Airforce gun's barrels to have. Now. I wish that I'd have gone with the 41 gr NOE BBT's, when they finally appear, for this barrel. No use crying over spilled milk though, I'll immediately start looking into the GM barrel, which Rsterne, Bob, says has a 1-16" rate of twist. I want sub-moa accuracy with these bullets. By the way my gun, when shooting between 1008 fps and 1026 fps, shot the H&N Grizzly bullets, pellets into 3-shot, 3/8" groups at 50 yards, consistantly. At 1039 fps the group size was 1/2"-5/8", at 50 yards. 1100 fps would open group size to 1 1/8" and at 1123 fps group size grew to 3 1/2".
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Kirby, those photos are great. Thanks for posting them.
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I have never measured the MRod .25 cal GM barrel, but the specs I have seen, confirmed by some on this forum, is a 15.5" twist rate....
Bob
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If your looking to change the barrel why not go to the 25 auto TJ barrel. 1:14 .250"
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"If your looking to change the barrel why not go to the 25 auto TJ barrel. 1:14 .250"
Maybe that's where I'll end up, but I want to try the GM barrel first.
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The NOE sizing stuff showed up yesterday, but I had other commitments and didn't get to the shooting bench until this evening. I had prepared about 450 bullets for sizing, over the weekend. These were tumble lubed with straight Johnson Paste Wax and then dried. I resized about 100 bullets through the .256" bushing. I then put them all back in the glass mason jar and tumble lubed them again with the residue of wax still left in the jar from the first lube. I then let these dry, on waxed paper, again. This evening there was still enough light left to chronograph some 3-shot strings. I adjusted the power setting until I was satisfied with the output curve. I ended up with a 3-shot average of 951.3333333 fps. 9 of these bullets weigh an average of 52.77777778 gr apiece. Average energy for 3-shots, with the guns present settings, is 106.1 fpe. I had company show up and after they left it was really too dark to start shooting groups, but I did shoot one group, at 50 yards. I didn't get the caliper out, but I could see it was right at 5/8", for 3-shots. That's actually quite encouraging as even when I had this gun, with another projectile, shooting 3/8" 50 yard groups, in this same lowlight I'd usually get 3/4-1" groups.
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Not sure about lubing your bullets. I use imperial sizing wax and only put a little on my finger to rub on a bullet. I do that about every 10 bullets to make sizing easy.
Also what size is your barrel? .256" seems awful large for a .25
I found your barrel size. Try shooting smaller. .001" in my opinion is to much. I don't shoot more then .0002".
Did you check the bullets after sized?
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Not sure about lubing your bullets. I use imperial sizing wax and only put a little on my finger to rub on a bullet. I do that about every 10 bullets to make sizing easy.
Also what size is your barrel? .256" seems awful large for a .25
I found your barrel size. Try shooting smaller. .001" in my opinion is to much. I don't shoot more then .0002".
Did you check the bullets after sized?
Basically, I got into this NOE 51 gr BBT bullet casting thing pretty much not knowing anything about bullet-size/bore-size relationships. Thankfully, Bob steered me right, or I'd have bought the wrong mould size. At the time that I ordered the sizing components, last week, I was believing that my barrel bore was .254" and that it had a 1-16" twist. So I ordered 3-sizing bushings, along with the universal die, from NOE. The sizes that I ordered are .254", .255" and .256". After placing my order, I also spent a whole lot of time reading various forum threads on both the subject of bullet-lubrication and bullet-size/bore-size choices. One thing that really stood out was that it was stated that undersized projectiles is the no. 1 cause for barrel-leading. Also an oldtimer, that has been lubing his rifle bullets with Johnson Paste Wax, for over 30 years, then in 2013, went on to say that most people feel safe from barrel-leading by shooting .001" over bore-size bullets However, he said that because of manufacturing inconsistancies in the length of a bore that he believes that .002" over bore-size is better choice. With all of this information I had already determined that I was only going to use the .256" sizing bushing. Then I found out that by bore is not even .254", but rather .255" and I have been agonizing over that ever since. And now you're suggesting that under .001" is better still. So, I have no idea who is right or wrong or why exactly.
No, didn't measure the bullets after sizing. I'll need to push a bullet through the sizer and measure it before I add wax. If I remember then I'll do that tomorrow, LW, and I'll let you know what I find.
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I have been thinking that If I want to use a lube I thought I gotta eat what I lube with... so I am thinkin bees wax and canola or olive oil or even tallow.. ;)
good enough for Eley.
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Who says barrel leading is from under size bullets?
30 years must be PB. What works for PB is not the same for air.
We are dealing with 3000 psi and not 50,000 psi. Shooting that much over size is just wasting fps. I know shooting a .0005" larger then needed is about 5' at 400 yds lower.
When getting groups the size of a asprin or barely larger at 100 yds using bore sized slugs or .0002 " under is not proof enough to what works then I don't know.
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Also I have a LW 24" unchoke barrel here. When I slugged it the first time the bullet came out larger then it was when I put it in by about .0005". There is a lot lead to move because there is 10 grooves.
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I decided to listen to what you were telling me, Doug. If anybody knows this stuff, it's probably going to be you. So early this morning I sized several of these bullets to .255". By the way, the .256" sized bullets measure .25607". I was also displeased with the Johnson Paste Wax as yesterday group size began expanding until I pulled a very tight, brushless, bore-snake through the barrel. Since these .255" sized bullets already had wax on them, I dropped a small drop of Lee Liquid Alox into the bottom of the mason jar that I use to tumble lube with. I also added a very small drop of mineral spirits, put the bullets in the jar, screwed down the lid tightly and began tumbling these under the kitchen faucet while hot water was running. The hot water melted the wax on the bullets and allowed this wax to mix with the LLA and mineral spirits. This lube is known as 45-45-10 lube. After tumbling about 5-mins. I dumped these out on waxed paper to dry. They dried all day and in the afternoon I collected these bullets up and went out to the bench. Here's a picture of the first, and only, 50-yard group that I shot:
(http://i38.photobucket.com/albums/e127/kameradrei/_1020827_zps9m77shr6.jpg)
The small red dot, by the two holes, is the first shot. Since it wasn't on the big red dot and since the shot was a bad one, in that I closed my eye and couldn't call that shot. I thought that I pulled the shot off course and so I covered it with a piece of tape and marked it with a small red dot for reference and I went back to the bench to start the group over. You can see where the next two shots landed. After shooting this I had to go somewhere and I didn't return until after dark, but this is most certainly encouraging and it appears to be a step in the right direction. Thank you for taking the time to correct some of my misconceptions, sir. I really do appreciate that!
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If you want to try something else get some imperial sizing wax. Comes in a pellet tin type container. Trying sizing with that only. Then shoot them. I only lube to size and that's it.
If you have the ability to open up a sizer then you can buy a under sized one and open it up to just under bore size.
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It is looking very promising... sub moa at 75 looks very likely to me... 121 a challenge but doable... .
Thanks for sharing the challenge...it looks like killing the Choke paid off well... the barrel being short probably took away enough lever to handle well harmonically at ~100 fpe... that is a feat...for a .5" O.D. barrel...
When you lapped I get the impression it might have been a poured lead lap used?
It may be a while still but when the 41g mold is done and I get the hang of casting I will send you a few of them so you can check out how they do.
right now I just have recovered pellets to melt... but will get some 99% lead soon...
I have a bunch of rosin core 60/40 solder I wonder if that will work for the tin content...
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hey Bob check it out, not the only persons that thinks a rebated tail is a good idea ...1992 filing check out image #3
https://www.google.com/patents/US5275108 (https://www.google.com/patents/US5275108)
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Interesting use in a subsonic .22LR rimfire cartridge.... Corbin have lots of information on rebated boattails on their website which I found very helpful.... and of course the Lapua subsonic bullet for the Whisper (AAC Blackout) as well.... The only thing I did was to apply it to airguns....
Bob
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Here's my story. I decided that the wax lubrication was a terrible idea, so last night I boiled all of the bullets that I lubed, about 375 which I hadn't shot, in a pot of boiling water. The wax, and Lee Liquid Alox, floated to the surface. I poured off the wax and water and dumped the bullets out on a towel to dry. I then relubed about 80 of them with Krytox GPL201. A single tiny drop in the bottom of a screw lid pellet tin was more than enough for 80 of them. After swirling these around in the tin for several mins, I then sized these to .255", put them back in the tin and swirled the tin around for about 5-mins to get the newly exposed surfaces, from sizing, lubed as well.
Today the gun shot several .25" groups, at 50 yards. And this it did at an average power of 110.86 fpe. This is far better than I had ever hoped to see from these bullets, in this gun. I'm now looking forward to see what happens at 121 yards (the extent of my range.)
So thank you, very much Bob, for designing this mould for NOE. I'm extremely happy with this mould, now. I thought for certain that I was going to be changing barrels soon, after finding out about the 1-17.22" twist. I'm very glad that I don't have to, now. And a very big thank you to you Doug. If you hadn't stepped up and steered me in the right direction I probably would have never got this gun/bullet combination dialed in.
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Excellent news. I'm using the same 1:17.22 twist barrel in my BT65. Can't wait to start casting and shooting these new BBTs .
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The lowest tin/lead alloy I could find at Roto was 2.5 percent, but I also have pure lead. Should I try alloying the 2.5 percent to 1.5 using the pure lead, or just use it like it is?
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Buy some of the pure tin pellets they sell. They are .6 ounce ea so it's easy to add to your lead. I mix my lead at 1% and that's what I use.
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I buy the "popcorn tin" from Rotometals, it's easy to weigh and you don't have to cut it, just break off what you need.... I have been using 1% tin, in their pure lead, but seem to be gradually increasing my tin content.... I think next time I will buy the 40:1 (2.5% tin) and try that....
Bob
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I buy 40 to 1 just the simplicity and it flows well.
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On Monday afternoon, early this week, I sized some of these bullets with the .254" die. These measured .25385", approximately. I didn't expect much from these "undersize" projectiles, because the bore diameter of the gun's Lothar Walther barrel measures .255". I only shoot 3-shot groups, so many won't find my findings very useful. The very first group that I shot with these .25385" dia. bullets landed in the middle of the 50 yard target's 5/8" dot and ctc the variation was about 1/8"... a ragged single hole. Thinking that this just had to be a fluke, I shot several more groups, but they were all very tight like the first with the largest about 3/8". I was/am, extremely pleased with the way these bullets were/are shooting, now. So Tuesday and Wednesday evenings were dedicated to sitting on a hillside, overlooking the garden, waiting for woodchucks to appear. I killed two woodchucks. This evening, Friday, I decided to shoot at the 50 yard target. I shot 3-shots and walked out to the target. A single hole the diameter of a single bullet is what I was looking at. Sub 1/16" ctc, probably. I have no idea how to actually measure something like this. Again, Doug wrote recently that he slugged his LW barrel and that the 10 lands and grooves resized the bullet's diameter into a larger diameter than it was originally. This must be the reason why this is working so well with these .25385" sized bullets. I still haven't had a chance to shoot these at my 121 yard target. I'm hoping to get to this weekend, though.
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Glad to see you are getting good results.
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These are great results, and certainly show the merit to at least trying bullets that are slightly undersize.... I would like to thank Doug for letting us in on this little secret, and to Owen for proving it can work.... You can bet I will be trying this in my guns as well, particularly those where I am having trouble getting good groups....
Bob
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Looks like I'll have to get myself a sizing die or two from NOE. Great results .any idea how fast you're pushing the slugs . Sorry if I missed it .
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Looks like I'll have to get myself a sizing die or two from NOE. Great results .any idea how fast you're pushing the slugs . Sorry if I missed it .
972.5 fps. 9 of these bullets averaged 52.77777778 grains each. Average energy was 110.86 fpe. However, over the weekend I made a new valve-stem. I chronographed these BBT 51gr bullets, using the same settings as the previous valve-stem, but the new one only achieved 959.9 fps average. Because this is basically the same output as what the previous valve-stem gave, I bored the old valve-stem out to a .234" bore (it was .221".) Since it was dark when I did this, I put the chronograph under an incandescent light bulb, as a light source, and the first shot gave a reading of 1027fps. I'll have to wait until I shoot across the cronograph in sunlight to be certain that this is correct though.
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Well 1027 fps over the chronograph under an incandescent light bulb equals 960.3 fps in daylight. I knew that there was a reason that I didn't use the chronograph indoors, but I couldn't remember why. I do remember that a 100 watt LED bulb gives the same type of error, too. Maybe fluorescent bulbs work?
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If you are using lights indoors, you need two, one over each diffuser.... A single light source, centered over the Chrony, will give a high velocity reading, and the lower the light, or the higher above the Chrony the pellet path, the greater the error.... This is because the light travels in a straight line from bulb to sensor, and from a single source, those lines are converging towards the light bulb.... reducing the distance the velocity of the pellet is measured over....
You want two incandescent bulbs, one above each diffuser.... Do NOT use fluorescent, the flickering messes with the readings as well.... Battery powered LEDs are OK, some AC powered units also flicker (but some don't)....
Bob
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Thanks a whole lot, Bob. I'll try to rig something like that up. It would be great to have it work indoors.
I am wondering now if I've reached the power limit (approx. 110 fpe) with the 16.25" barrel length. I hardly think that it's worth buying a 24" LW barrel to turn down and cut the muzzle end back to 19.25" (the maximum barrel length that I would put in this particular airgun.)
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If you plot velocity vs. power setting, you will eventually find a plateau for any given pressure and barrel length.... Trying to get more (what I call operating on the plateau) only wastes air, basically because you still have the valve open after the bullet has left the muzzle.... If you back off only a few percent on velocity from that plateau, you can literally save half the air without any significant drop in performance.... When the valve closes with the bullet only half way down the barrel, velocity has usually only dropped by about 3%.... while shot count has doubled....
Bob
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Excellent news. I'm using the same 1:17.22 twist barrel in my BT65. Can't wait to start casting and shooting these new BBTs .
Does this mean that the "stock" barrel on the BT65 .25 cal is a 1:17.22 twist? Is it the same bore as Owen's barrel? Mine is a QE model, so I'm assuming it's a choked barrel. What does that do to the accuracy/energy? How many shots would the BT65 get when tuned to approx 100fpe? Very interested in this mold.
thanks,
Ken
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The Hatsans BT65 and AT44 use the same twist as the Lothar Walter barrels . I have a LW barrel on my BT65 that I have confirmed to be 17.2:1 twist with the choke removed . As far as shot count goes a full mag of 9 shots should be possible . Of course it depends on how you've tuned the rifle . I've found the BT to be more efficient than the AT at stock power levels , I believe that is due to the hammer rebound device design.
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Using 34 gr. JSB Heavies in my AT44 Long, which has a 230 cc reservoir, I get 12 shots within 4% ES, with the best 9 within 2% ES, and that is at 70 FPE, at an efficiency of 1.15 FPE/CI.... The BT65 has a 280 cc reservoir, but I think you might be hard pressed to keep that efficiency at 100 FPE.... With the larger reservoir, you should be able to get about the same shot count I did at about 85 FPE (with 43 gr. Eunjins, for example).... At 100 FPE with a 51 gr. bullet, I think 9 shots might be difficult, but not impossible.... The ES would be the question over that long a string....
Bob
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Bob,
There is another thread where someone asked about .25 cal guns able to produce 100fpe+. You had commented in that thread on the bore in my BT65, but have removed the comments. Do you know the diameter of the Hatsan .25 cal barrels bore? Just trying to figure out which mold I need if I decide to go in this direction. I have 100+ lbs of lead and some casting equipment, just never done any real casting yet.
thanks,
Ken
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I think you will find that the Hatsan barrel is about 0.254" groove, like the LW barrels.... I know that my as cast 51 gr. BBTs, which measures 0.2535" at the drive band, did not get any marks on the drive band from the groove portion of the rifling, although the lands were deeply engraved on a bullet chambered and then pushed back out the breech.... There was "some" resistance to closing the side lever, which led me to believe that if you bought the larger size mould (0.253/0.255") you might have to massage the chamber by tapering the leade or they would be difficult to chamber.... Which size would shoot more accurately, and at what precise diameter, I do not know.... My .25 cal Long isn't tuned for a 51 gr. bullet.... I do have the 41 gr. BBT mould on order, though, in .253/.255 and I hope it will be just the ticket in that gun....
Bob
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Yes, I saw the mold for the 41gr boolits, but I haven't seen any groups that anyone is shooting with it. I also saw in a thread where you had mentioned milling a few thousandths off of the back of the 51 grain, so that it would throw a 45-48gr boolit. That may be an option for me as well. I don't know if I want to try making a D-reamer to make my own mold. I did make one for casting .22 50gr. slugs for swaging .223 bullets.
thanks,
Ken
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A few days ago my airgun's grouping at 50 yards, shooting the 51 FNs sized with the .254" bushing, they measure .25385" approx., opened up to 1.5". I spent the last few evenings trying to get to the bottom of the problem. This evening I used a bronze brush to clear the bore, sized a bunch of bullets with the .255" bushing and the gun now is shooting 1/4" to 3/8" groups, 3-shots at 50 yards, again. All of the bullets that I sized with the .254" bushing were dumped into a can of scrap lead, to be recast at a later time. It did work for a while, but now that is over. As Doug suggested, I may also resize the .254" bushing to size a couple of ten thousands under bore diameter. Also, I worked on my new valve stem some more and with it in the gun the .255" sized, 52.77777778gr 51FN BBTs are now averaging 978fps for an average of 112.12fpe.
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I've got the same barrel measurements as Bob if not slightly over. This is a BT65 stock barrel.
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Dang Owen that thing is hitting hard!
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Owen, did you by any chance try the .254's after cleaning the barrel?
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The 41 gr. molds are not made yet, so it would be difficult to see any shooting results.... I understand the Last Call on that Group Buy is about to end and the are going to go on the Mill....
Bob
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That would definitely explain why not shooting results. LOL! Looking forward to great results!
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I finally got around to measuring the .255" sized bullet's drive band. It measures .25480", which is exactly .0002" under my bore diameter and is also what Doug says that he sizes his bullets to. I tried to shoot a 5-shot, 50-yard group, today. The first 4-shots went into a single hole, probably 3/16" ctc as the hole was about 3/8" diameter. The center of the 5th shot's hole was 1/2" to the right of the edge of the first 4-shots. I took a 6th shot and it landed about 3/8" to the left of the first 4-shots and about 1/8" high. So I called it a day. This evening I removed the tank and moderator and thoroughly cleaned the barrel with a bronze bore brush, loaded with Hoppes no.9, then another bronze bore brush loaded with JB compound. Wiped out the JB compound, then bronze brushed with Hoppes no.9, again. Pulled patches until they came out clean, then finally I pulled the brushless bore snake through the bore. Hopefully this restores the accuracy that I enjoyed, before I, probably, leaded up the bore shooting such undersize (.25385") bullets through for a short while.
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Bob, I had to rezero with a new set of rings, I broke the rear ring of my other set, so here's an image of the last 3-shots that I shot at the 50 yard target, this evening, not zeroed yet:
(http://i38.photobucket.com/albums/e127/kameradrei/_1020832_zpsx2ps3kyg.jpg)
This is typical of how the NOE 51-FN BBT's are shooting from this LW 1-17.22" twist barrel, at 965-980 fps. Is it possible that the 1-14" TJ's .25-Auto liner could stabilize a heavier 63-67 grain bullet well, at airgun velocities of 1000-1050 fps? If so, is it possible that you'll design something like that in the future?
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Does anyone have any 100 yard groups with these bullets? 50 yards is OK but many bullets are accurate at 50 but are not at 100. I would really like to see these at 100 yards. I will offer this bullet if it can shown to accurate at longer ranges.
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Bob, I had to rezero with a new set of rings, I broke the rear ring of my other set, so here's an image of the last 3-shots that I shot at the 50 yard target, this evening, not zeroed yet:
(http://i38.photobucket.com/albums/e127/kameradrei/_1020832_zpsx2ps3kyg.jpg)
This is typical of how the NOE 51-FN BBT's are shooting from this LW 1-17.22" twist barrel, at 965-980 fps. Is it possible that the 1-14" TJ's .25-Auto liner could stabilize a heavier 63-67 grain bullet well, at airgun velocities of 1000-1050 fps? If so, is it possible that you'll design something like that in the future?
Correct me if I am wrong but wouldn't you have to be pushing 140-150fpe to push a cast boolit of that weight at that speed???
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Bob, I had to rezero with a new set of rings, I broke the rear ring of my other set, so here's an image of the last 3-shots that I shot at the 50 yard target, this evening, not zeroed yet:
(http://i38.photobucket.com/albums/e127/kameradrei/_1020832_zpsx2ps3kyg.jpg)
This is typical of how the NOE 51-FN BBT's are shooting from this LW 1-17.22" twist barrel, at 965-980 fps. Is it possible that the 1-14" TJ's .25-Auto liner could stabilize a heavier 63-67 grain bullet well, at airgun velocities of 1000-1050 fps? If so, is it possible that you'll design something like that in the future?
Bloody fantastic shooting. i can't shoot JSB's that tight at fifty even on a good day . I should probably lay off the coffee .
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I have designed several heavier BBTs, but they are designed for .257 cal barrels, not airgun barrels.... Once you cross the 100 FPE area, and are looking at 65 gr. and heavier bullets, everyone seems to want to go for the .257 cal.... There is a TJ's .257 barrel available with a 14" twist (for the 25-20) and the most popular bullet for it is the Lyman 257420, which drops at about 73 gr. in pure lead.... It is also available from Arsenal Molds as a boattail version at a couple of grains less.... I have several BBT designs at NOE, the 65 gr. and 78 gr. are both in Group Buys at present.... http://noebulletmolds.com/smf/index.php/board,26.0.html (http://noebulletmolds.com/smf/index.php/board,26.0.html) .... The 65 gr. is intended for the 14" twist.... My suggestion is that if you are contemplating a heavier bullet and higher FPE that you go for a .257 cal barrel, because of the much wider range of bullets available....
Bob
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@customcutter Yes and I figured up to 165 fpe. The Airforce platform, which is what I'm using, has been taken up to, at least, 500 fpe.
@Hobbyman2007 I usually take a cup of coffee with me to the bench, to drink before I begin shooting.
@rsterne Thank you, very much, for taking the time to let me know all of that information. That's probably the way to go, for sure.
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I finally got my airgun zeroed at 50 yards, so I decided to shoot a 3-shot group at 121 yards (the extent of my shooting range.) All 3-shots landed in the 1 3/8" red circle and formed a 3/4"-7/8" group. This confirmed at least two things for me. One being that the NOE 51 gr BBT bullets are shooting great through the Airforce Lothar Walther barrel, at the 111-112 fpe level. And two is that my scope's reticle is not tilted (I had to remount the scope with different rings, as I broke the rear ring of my first set.) Again, I'm exceedingly pleased with how well these bullets are shooting for me. Thank you, again, for all those that helped me to get these bullets to shoot like this.
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WOW !!!.... Sub MOA at 121 yards is GREAT !!!.... Thanks for keeping us updated with your success....
Bob
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This is getting rather interesting. Could we see some 5 or 10 shot groups at long distance Owen? Is that LW barrel of your's choked?
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unless he changed barrels he sent me the choked part and the length is 16.25" L.W. 1:17.2 twist...
I wanted to be able to post pics of the Trail .25, Mrod .25, And L.W.(Air force) .25 rifling for this thread... so thanks again Owen. :D
so here is a quote of where Owens is barrels at...
"
my barrel length is presently 16.25", 18" Airforce barrel with 1.75" removed (chokeless, now.)
"
wish I was rich I would pick up a .25 BSA hammer forged barrel to see if I could make it work... But honestly I would want a CZ ultra lux .22lr barrel to try first...
Me I am pretty happy to see that if you have the fpe and get it out of the barrel right, even with a slower twist they fly very strait... it bodes well for the 30g .22 BBT as they are very similar... and both evoke Eley Tenex to me...
would love to see some 43g and 46g or even just a 45g .250 BBT as time goes on
not to mention more .22 BBT on up to about 45 gr... ;)
I really like it down at .22... because just by putting a 24"-28" barrel on the .25 Mrod platform ( probably have to semi float it) you should have the fpe needed up to about 40-45 grain projectiles...
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I have one friend who tested that bullet on two LW's barrel. One was 12" twist and he didn't get any good results and other was LW's airgun barrel at 16" twist no choked and no good results. But not sure how encompassing test was. I mean did he tested several different shooting pressures etc..
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Things have been crazy busy here for a while, with moving and such, but I was finally able to launch this bullet at s target. The gun is a Condor SS with the 18" .257 barrel from R&L and Talon Tunes heavy spring and Quick Change Top Hat with no insert. The tank was filled to 3000 psi, and the power wheel set to 2-7. I have not yet found my chrony in the moving chaos, so I dialed in the power level to where it just penetrates a steel barrel. I sighted in the scope with a few shots, and the final three are the actual targeted hits. I was shooting standing with the gun semi-supported (muzzle resting on s trash can) at about 60 yards. All three shots are inside and inch with two touching! I can't wait to see what it will do off a bench with a little more practice.
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Wow that is amazing a 253/255 round doing that well out of a 250 bore/257 groove barrel..! 1:14 twist I think
I notice on the R&L site they also state that it is good with 25g JSB Kings..? :o
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Yes, I did get the .255" diameter mold, but I think the bullets may be dropping from the mold a little bigger than that, as they were impossible to load into the AirForce barrel without using a substantial steel tool, and even in this barrel they still offer some resistance to load, but they will load with finger pressure.
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well the nose being around .253+ gives .0015+ engagment with the lands and the drive band about .0025 engagement... so it is basically bore riding...
But sealing..? it still leaves about .001 till groove contact... now if barrel groove is actually tighter at about .251-252 and the rounds drop a bit big..?
Bob stated that his .250/252 were droping about .0015 large so maybe just enough for the drive band to swage out a bit because of the tall lands...
about how wide are the lands bearing surface..?
The L.W. and Benji .250 barrels are about .03 wide with ten lands and grooves which gives about a 60/40 groove/land ratio which can help give an idea of how much they will swage the round with their lands (along with their height of course)....
I think that The T.J. barrels are six land/groove so if they are ~.3 wide that gives groove/land ratio of ~ 75/25...
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unless he changed barrels he sent me the choked part and the length is 16.25" L.W. 1:17.2 twist...
I wanted to be able to post pics of the Trail .25, Mrod .25, And L.W.(Air force) .25 rifling for this thread... so thanks again Owen. :D
so here is a quote of where Owens is barrels at...
"
my barrel length is presently 16.25", 18" Airforce barrel with 1.75" removed (chokeless, now.)
"
wish I was rich I would pick up a .25 BSA hammer forged barrel to see if I could make it work... But honestly I would want a CZ ultra lux .22lr barrel to try first...
Me I am pretty happy to see that if you have the fpe and get it out of the barrel right, even with a slower twist they fly very strait... it bodes well for the 30g .22 BBT as they are very similar... and both evoke Eley Tenex to me...
would love to see some 43g and 46g or even just a 45g .250 BBT as time goes on
not to mention more .22 BBT on up to about 45 gr... ;)
I really like it down at .22... because just by putting a 24"-28" barrel on the .25 Mrod platform ( probably have to semi float it) you should have the fpe needed up to about 40-45 grain projectiles...
I could give them a go in my BSA barrel as Teemu has the mold, although I'm not going to remove the choke. With a choked barrel, how should the bullet be sized? I tapped a pellet to widen it a bit, pushed it through and measured 0.2545. Should I try 0.254 bullets then?
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well I think we need to know more... the barrel is it the ~19" long barrel... and is it about 1:19 twist( it is my impression that is the twist on all the BSA barrels?) # or lands, height and width and aprox fpe you can muster up with Jsb heavy or 40 grain Eun Jin...
will not have to worry as much about harmonics as they are pretty stiff but is the receiver and all up to the fpe..?
I do think these 50 grainers should be launched with at least 75-80 fpe is the main prob... at 50 fpe that is only about 670 fps...
It would be like trying to run .22 subsonic in a CZ barrel with its tight bore (about .212) but magnified... they recommend against it... but up around 100 fpe it works...
Scroll down to the question “I’ve heard you use tight bores in your .22s, is that right? What does that mean?”
http://cz-usa.com/support/faq/ (http://cz-usa.com/support/faq/)
Point is you are probably better off with the 40g .250 BBT...
but
hey ya never know it might work...
in theory I would try to bore ride it as much as it will take and size as little over groove size at the choke as possible...
and then if that did not work I would size a bit smaller and knurl back up to size... to make it as easy as possible to get thru the choke and it still might not work... even with the 40g .25 BBT...we are in uncharted waters...
scroll down to reply #12,
http://castboolits.gunloads.com/showthread.php?111103-Cast-bullets-for-the-22-Hornet (http://castboolits.gunloads.com/showthread.php?111103-Cast-bullets-for-the-22-Hornet)
I will even try paper patching to help get it thru the Mrods choke when I finally get going if I can not make it work any other way...
My back up plan is also ~ 1:19 twist (but unchoked) which suits the 40g .25 BBT better than the 50 grain...
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well I think we need to know more... the barrel is it the ~19" long barrel... and is it about 1:19 twist( it is my impression that is the twist on all the BSA barrels?) # or lands, height and width and aprox fpe you can muster up with Jsb heavy or 40 grain Eun Jin...
will not have to worry as much about harmonics as they are pretty stiff but is the receiver and all up to the fpe..?
I do think these 50 grainers should be launched with at least 75-80 fpe is the main prob... at 50 fpe that is only about 670 fps...
It would be like trying to run .22 subsonic in a CZ barrel with its tight bore (about .212) but magnified... they recommend against it... but up around 100 fpe it works...
Scroll down to the question “I’ve heard you use tight bores in your .22s, is that right? What does that mean?”
http://cz-usa.com/support/faq/ (http://cz-usa.com/support/faq/)
Point is you are probably better off with the 40g .250 BBT...
but
hey ya never know it might work...
in theory I would try to bore ride it as much as it will take and size as little over groove size at the choke as possible...
and then if that did not work I would size a bit smaller and knurl back up to size... to make it as easy as possible to get thru the choke and it still might not work... even with the 40g .25 BBT...we are in uncharted waters...
scroll down to reply #12,
http://castboolits.gunloads.com/showthread.php?111103-Cast-bullets-for-the-22-Hornet (http://castboolits.gunloads.com/showthread.php?111103-Cast-bullets-for-the-22-Hornet)
I will even try paper patching to help get it thru the Mrods choke when I finally get going if I can not make it work any other way...
My back up plan is also ~ 1:19 twist (but unchoked) which suits the 40g .25 BBT better than the 50 grain...
18.5" barrel. Twist rate about 17-18:1 (measured half turn), 6.46mm bore at choke and I'd guess around 6.35mm (0.1mm accuracy, could be 6.30 just as well) lands. I'm throwing 34 grainers at 890 fps so I hope these 51 grainers would fly around 750 fps as the barrel length is limiting power. If they are accurate with the barrel I could do some mods later and probably reach around 800 fps.
The barrel is pretty loose with JSBs up to choke so I'd guess bullets could be bore riding up until then. However, what happens at the choke is then another matter. There's bound to be some lead expanding to the grooves so as 6.46mm = 0.2543" I'd be tempted to try 0.254 die for perfect sizing. Of course I could try 0.255 as well but that would then be 6.477mm which seems a bit too tight.
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I cast my first batch of two hundred yesterday , unfortunately they won't chamber. They drop as cast at .256 to .257 according to my cheap mic. These were for the .254 /.255 mold. Guess I'll have to wait for my sizer to come in . They look great for first time casting , was a lot easier than I originally thought.
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looks like they will hit hard! I always into heavy pellets. what will you use these pellets for like for hunting small games?
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Well I forgot , I had bought a couple dies and a lee press a while back. Sized to .254 and they are chambering just fine . Here's a quick string through the Hatsan BT65.
893
895
893
897
897
895
883
879
Start fill at 2900 , end at 2250 . That's averaging 90 fpe for 9 shots . Now for accuracy testing .
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Here are my findings . I sized the solids to .254" and the hollow points to .2545 " . The solids shot a lot better 1" at 50 yards vs 3" at the same distance both at 900 fps .When I cast these ( first timer ) I used a 25:1 ratio of lead tin mix . I think they may be a bit too hard . The good news is that they are shooting pretty well . I'll keep working at it hopefully post some pics of my groups next time out .
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I got to thinking about when Owen ran these loose and was getting good accuracy but they leaded up quickly.
Nick initially got good accuracy even at lower velocity/slower twist and then they lost accuracy pretty quickly(probably leaded up the choke?)
and then they show signs of doin' well in Tom's .257 barrel and have to be a bit loose in it...
and I am worried about leading the choke on my Mrod when the 40g molds get made...
So I got to thinking I just may copper plate them to see if that will help prevent it... all you need is some root killer(copper sulfate) from the hardware store, copper wire, water and some d batteries... Heck been thinking of trying it on some pellets for a while since even Crosman is putting some out now...
so my point is if they star tout well in your barrel and then loose accuracy and you find leading... the prob might be fixed with copper plating...
Somewhere in my junk I have a low amp power supply and a collection of wall warts...
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Here are a couple pics of shooting at 80 yards. The first two are with the solids ,and the third is with the HP's. Not my best shooting but acceptable for hand cast bullets . None of which were perfect I might add , I'm still learning how to cast right now .
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can not see well enough are those rips or yawing bullets in the pics?
I for practice, have been pouring some Bator 225-55-rf and the new 225-55-rf... the big sprue hole(~.140) is causing some slight base distortion... I think about .125 would be about right... I have been slow and opening with an old hammer handle... next session will try right after flash and shrink... with a gloved hand... I wonder if lee sells blank sprue plates. They do sell blank Molds guess I will have to contact them and find out...
being sloppy with big sprue puddles on the plate seems to help fill out. No probs with sicking until the Bator mold got real hot I slowed a bit and they stopped sticking...had to tap the handles with the hammer handle till it cooled just a touch...
lots of little thing to figure out... I see it as a fun challenge in problem solving for each round/barrel/powerplant and that is after getting the mold/pour right...
I am hoping in the long term to use the Lee molds to make a few (8) different .22 rounds by decking them (pics below).
So the Bator full size @ ~50g...
Decked to the back of the rear band removing the gas check comes out a flat base about @ ~44g...
decked to the front of the rear band comes out to a heeled round about ~36g...
and decked to the back of the front band comes out a flat base about ~31g (if it can be decked that far)
then with the new 225-55-rf
Full size is About 55g
decked to the back of the rear band gives a flat base round ~48g...
decked to the front of the rear band gives a heeled round ~41g...
decked to the rear of the front band gives a flat base and ~35g... once again if it can be decked that far...
I was a bit lazy with how measuring much solder(60/40) with the melt I think its about 4-5%Sn and .5 sb (from the crosman pells) because it was recycled pellets of many makers...still have more did not even have to add the bit of plumbers lead I found in my neighbors yard.
have a couple sizing die ~.2238 and ~.2244 so sized a couple and then did push thru thru a old seasoned model 60 .22 lr barrel and and new unfired 883n .22 WMR barrel...
at .22 the base distortion just might be sized out to a great extent... the .224 (WMR)barrel does not engage the gas check so it still matters with it for sure...
Along with the 40g .25 BBT and the 30g .217 and .220 BBT to figure out and experiment with... it looks like a couple years of fun learning and hopefully mastering small bore cast with air power...
So yep I am casting for a rifle I do not have yet.. ;) But the first step is making the best cast possible and I need to practice and develop a routine techniques and such so I am remelting about twice a week... with the tiny lee pot and a Lyman ladle.. ;)...
I have cast Aluminum as a job and watched boolit casting and have the eye net to help so have a good bit of confidence I will get there...
well any ways if the pics were a bit better might be able to read the targets a bit... distorted bases and other casting flaws can show up as yaw even lead to instability... So yep good fill out on the bands/base no voids and wrinkles etc...
I was pretty amazed that towards the end of the first casting session they were dropping very well... I figured it might take some cycles to heat and cool before that would happen...
all I did for mold prep was to wash with dawn and let dry and then some sprue lube...
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If you still have the full size pics if you want email them to me and I can crop and size with windows paint to maybe get better detail...
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I grabbed an image and rotated it and enlarged a bit... what the rips might be hinting at by all being towards the same-ish angle is poss0ibly a very slight yaw..? hard to tell... could just be the way the paper hangs...
edit added image*
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earlier i spoke about CZ 22lr barrels at about 100 fpe...went looking and found this... I think it shows a bit of how picky barrels can be...in real world conditions
https://www.youtube.com/watch?v=cR7b3fx8kVk (https://www.youtube.com/watch?v=cR7b3fx8kVk)
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I don't think the bullets were keyholing, the back board I stapled the paper to was on a pretty good angle . I did notice after the first 20 or so that I cast that they were not filling very well , unless I got sloppy and had a big puddle on the sprue plate and letting them cool for a five count before cutting.
I should also mention I'm a horrible shot . Lol
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I recommend use thick welders glove or piece of thick leather to open sprue plates. If You knocked mallet or something else Your mold may get some damages. I never use anything else but glove. Just my 2c..
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No pics this time . Shot out at 110 and 170 yards today. This time with a 40:1 mix and the results were much better. 2 " to 2.5 " groups at 110 yards and 4" to 4.25" at 170 yards. I should mention the 10mph cross winds . I'm completely impressed with these bullets , as I don't think I could have done any better with my magic pellet ( jsb heavy mk1 ) for this rifle at that range . Good job again Bob , loving the heavy ammo in the BT65 . Now to get my hands on the .22 version of the mold. I've got a disco bottle gun waiting for them. ;)
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It may very well be that in order to get heavy enough bullets to work in the more commonly available slower twists we may not be able to take advantage of the boattail.... That would be a shame, but it could, unfortunately, be reality.... We may be locked into draggy, flat-base bullets by the barrels that manufacturers choose to use.... Boatails may become toys for those few who can afford to replace barrels, or build PCPs, to match their capability.... :-\
It goes deeper than twist rate, of course.... The lack of standardization of bore diameter in airguns is atrocious.... PB's don't have a problem coming up with a standard, why should it be so difficult for airguns?.... The only reason I can think of is that the skirted diabolo pellet has made it so easy to get acceptable, close range accuracy with nearly any barrel.... The airgun manufacturers have become complacent, or is it the other way around?.... There were never consistent standards, so the pellet manufacturers have found a way to make (inflatable) pellet skirts that for the most part don't care what the bore diameter is.... A perfect example is how well the .300 cal JSB Exacts work in a .308 cal PB barrel, even though the head is nearly bore riding.... The skirt is large enough, and expands to seal, so all is good.... in a barrel that is 0.008" oversize.... ::)
It would be a shame if what could be a huge step forward in airgunning.... the ability to have a much lower drag projectile.... is passed over because the projectile has outstripped the barrels.... but I can see it happening.... It would be ironic that my attempt to modernize airgun projectiles, to keep up to the wonderful and powerful new PCPs we have, is defeated by their very inconsistency of design.... :(
Bob
I couldn't agree more. A stable lower drag projectile would mean a new level of range and accuracy to airgunners.
So why not a Diablo-Boattail that would satisfy everyone. The design in the attachment could be tested on one of Bob's longer heavier Boattails.
By just drilling the back of the projectile in a similar fashion to the attachment it would seal more barrel sizes, make it less heavy at the back for better stability and still have the drag reducing benefit of the boattail.
I don't see the attachment in the preview. If it doesn't show up I'll keep trying.
Ed.
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The hollow base is going to slow down the pellet. You need a solid base or boattail to have good BC.
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The BC would be better than a regular diablo.
Ed.
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I think you need to see the reasons the boattail works, it's not a magical shape. It disrupts the airflow behind the bullets because the bullet have a negative pull, an eddie behind it. That's why the longer the boattail you will have better BC. I believe the hollow base will still create that eddie.
The best way to test your theory is to have a mold made and test it.
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I think once you start controlling the air flow in the right direction (inward) after the rear seal of the pellet it goes a long ways to stabilize that flow. I've also recently seen transport trailers with flaps at the rear that although square represent the same principle as shown in the attachment.
I only predict a better BC than a regular diablo and that seems worth it to me.
It's a simple matter for someone with a drill press and machining skill to drill into the back of a boattail projectile like the pellet in the attachment I sent to test it out.
Ed.
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Won't work on bullets. You would bring the CG to close to center. That is why a lot of bullets don't work good because there isn't enough weight behind the CG.
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Here are a couple of groups at 103 yards lazered. These bullets were no where near perfect as I am still learning the finer details , but am getting closer . I think with a bit more practise pouring and getting the size and temp right I'll have a sub MOA setup in 95 fpe. I should mention I don't think I could do any better with the jsb pellets . Don't mind the flyers they are only proof of my casting skills .
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Got a chance to shoot some of the 51 gr .253 rounds this eve!Shot the HP version which I'm getting 48.9 gr dropping at .2551.Boy was I smiling.I didn't get a chance to sling but a few rounds cause light was fading fast but I got 1 hole 4 shot groups at 50 yards threw my AF escape.Its a stock gun,just bought it last week and I'm getting mid 900's on a power setting of 6.This gun is awesome.Will play with it more fri when I'm off..find the best power settings and shoot some groups.Upload some photos too.Seems the L.W. barrels love these bullets!!!
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Got a chance to shoot some of the 51 gr .253 rounds this eve!Shot the HP version which I'm getting 48.9 gr dropping at .2551.Boy was I smiling.I didn't get a chance to sling but a few rounds cause light was fading fast but I got 1 hole 4 shot groups at 50 yards threw my AF escape.Its a stock gun,just bought it last week and I'm getting mid 900's on a power setting of 6.This gun is awesome.Will play with it more fri when I'm off..find the best power settings and shoot some groups.Upload some photos too.Seems the L.W. barrels love these bullets!!!
Great news!!! Cant wait to see some 100 yard groups. Nice job.
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Me too! ;DI bought the AF Escape for accuracy!Period.I have several big bores that I have accurate rounds for as well but they are strictly hunting guns.If I get a 2 inch group at 55 yards...I can live with that.most of mine will do that a 80 yards but saying for the sake of my point :DI bought the escape to play with and shoot distance.This gun has exceeded my expectation so far.Wish the 357 Texan was even close.Id have bought that but....
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GTA Nation,
I've been working over the last few months on trying to perfect casting 51gr and 41gr BBTs. I've come a long way, but still have some work to do. So far everything seems far from the advice on forums I've read. I run my melt at 780-790 degrees (PID regulated) and preheat the mold to 380. Working a fast pace the mold settles to 360 or above. 360 is the temp I've found works best to keep creasing to a minimum. When recycling the sprue I have to sprinkle in some tin chips to compensate for any that oxidized off (from a base of about 1.5% Sn). The attached last attempt shows a dramatic improvement from the first! I'll eventually be shooting these from a TJ .25 ACP barrel, once I get the confidence up to machine and fit it onto a .25 Gladius.
Anyhow, this weekend the question popped into my head, "How good is good enough?". How much does a casting defect affect accuracy? This last casting session I saved what are my most common seen defects. Can folks who have more experience in casting and shooting their own boolits share some thoughts?
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Any wrinkling usually indicates you need to work at a higher temperature.... On small bullets like that I usually have to run over 800*F on the melt to maintain mold temperature....
Bob
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I would try to preheat the mold with a hot plate or other technique. Also keep your casting speed up. If you have an aluminum block they heat fast but loose heat fast too. If you have a steel or brass they take a lot longer to heat up but maintain the heat better. Those molds look cold.
Also if you are using pure lead you can try using an alloy with tin. You can find 40:1 pretty easy and ready to go or you can add tin by weight to come up with a tin alloy. I use 40:1, it cast good, can be bought ready to cast - just melt and pour and is still soft, around 8 BHN. You will find it much easier to cast with lead and tin because the tin makes the bullets fill in much better and will pour at a lower temp.
Also, preheat does mean leave a torch on them and burn them up it means to get them hot enough to get good bullets. A hot plate is a good way to let the mold heat up with out getting it too hot.
If you preheat your mold and use an alloy like 40:1 or less like 80:1 you should have much better and more consistent bullets.
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Thanks Nick/Bob,
I've noticed the high mold temperatures as well. One test this weekend, I heated the mold to 400 on the hot plate and cast with the melt at 720 degrees. The first handful of drops went well, but the mold temperature quickly fell off. With the melt at 780-790 I can keep the mold at 360, with descent results, but only if I go like a bat out of *(&^. Next time I'll try Bob's advice and go around 810-820 and see if my discard percentage gets better. Right now, about 30% of the drops go back into the pot.
I was more curious on advice on how small defects can affect accuracy. Take the 'Example 3' picture for instance. Is that amount of texturing on the cast something to consider as a defect or would it likely shoot okay?
Bob, on another note. I saw a tumbler the other day while at Harbor Freight (think those rock tumblers for kids). The thought crossed my mind of tumbling boolits in silica sand. Do you think there would be any merit in such an approach?
Thanks for designing these, I hope to be shooting them soon!
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I have tumbled bullets with no media, and it leaves them with a dull surface, with the base corners rounded.... I would be concerned with getting anything abrasive imbedded in the bullet and damaging the barrel.... I did not notice any difference in the way they shot.... I don't think your example 2 or 3 are an issue, the large wrinkles in #1, yes, I would discard them....
Bob
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We did one test last summer with TPL. We both own Corsair .308 and that was test gun. Both shot own guns. I shoot perfectly casted and weighted bullets and TPL shoot same bullets but not weighted and so horrible looking. Wrinkles allover and holes,grease gooves was malformed... But there was no significant difference those 10 shot groups which we shot. Distance was 100M.So I don't anymore check bullets before silhouette competitions etc. Bench rest is different thing..
http://www.sihry.fi/keskustelu/viewtopic.php?f=24&t=364&start=1270 (http://www.sihry.fi/keskustelu/viewtopic.php?f=24&t=364&start=1270)
Scroll down 9th post on top of page. There is pictures of bullets and those groups. Click pictures for bigger.. I lost one and win one 10 shot groups... We didn't shoot those groups like competition just for testing purpose,so we shot quite fast and that was results
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just my opinion... I feel if you are getting a nice sharp base on your rounds it is better than tumbling them and getting rounded corners... no proof just a gut level feeling...
Harry Pope in the old Days made a fixture to muzzle load his rounds... why..? to keep the base of the round as clean as possible... I drink that cool-aid and believe that it is among the most important aspects of the round...
this round is very similar to the .22lr in fpe and exterior ballistics... here is a vid of some deliberately badly out of balance and aerodynamically unsound .22 lr rounds at 50 yards...
https://www.youtube.com/watch?v=C9Dylxy3zJc (https://www.youtube.com/watch?v=C9Dylxy3zJc)
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Sure this test was just prove that some guns aren't so picky when it comes bullets. Of course when I cast bullets I throw wrinkeled and malformed back in pan
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Many cast bullets are NOT perfect at the corners of the base, because of the pressure of cutting the sprue.... This is worse with small calibers and large holes in the sprue plate.... with the base ending up rounded on one side, and super sharp on the other.... I agree that is once of the problems that destroys accuracy, and the bullets I tumbled were to even out the base.... One of the reasons I used a rebated boattail in my BBTs is to move the release point where the bullet leaves the barrel crown forward to the driving band.... and away from any base distortion due to casting and uneven sprue cutoff.... That's the theory, anyway, and the reasoning behind it....
Bob
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Does anyone know where a person could buy some of these Bullets? I have a .257 that I want to sell, and Bob recommends that I try these 65 grain Bullets. Just looking for 50 to get started, or finished.
Thanks!
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If i could find a type of slug like this, that would work in a .25 cal Condor barrel at .250 or so, i would buy the lee melting pot, and all the lead, to cast my own.... but i'm affraid to get into this....
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454,
Is your barrel choked? Have you slugged it to see what the exact bore diameter is? I would be willing to part ways with a few if you agree to post the results (you're not far from me as far as the USPS flies).
Regards
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you may have better luck but my LW 25 barrel did not like them.close range I got so so results...after 50 yards it looked like bird shot.I begal my mold to get a 257 dia and my T J barrel loves them.
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I'm in the process of fitting a TJ .25 ACP Barrel to a Hatsan Gladius, I hope my results are good as well. I have tried shooting them out of a BT65 with a stock barrel and the results were terrible. But, from prior posts in this thread, that's to be expected from a choked barrel.
If anyone has a TJ .25 ACP fitted and hasn't tried these, let me know. I can spot you some test BBTs (51gr FN, 47gr HP, and 41gr FN). I only ask that you post the results, hopefully will provide some motivation for me to finish this project and get to putting them downrange.
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I've cast almost 500 bullets from my new 253-51-HP 2-cav and fired them through my TalonP. I think I got the last 253-51 off the NOE store shelves! Pure lead FNs drop at 52.0 gr. exactly and the HPs drop at 49.1 gr. (with the pin adjusted as close to the print spec as I could get it). It's a fabulous mold. Nearly all bullets fall into adjacent 0.1 gr. sorting piles when weighed. I typically remelt only two or three bullets that don't meet +/- 0.1 gr. per casting session. That's better than +/- 0.2%, which is incredible consistency for a cast bullet!
After extensive testing in my TalonP at 50 yards, I could only achieve so-so accuracy, but so-so is all my TalonP can achieve with most pellets too. :'( The BBTs do their best from my short barrel / relatively low power TalonP at just under (FNs) to just over (HPs) 700 fps. My 5-shot groups are typically around 1-1/2 inches, which is about the same as I get with Kodiaks, Baracudas, and Benji Domes. JSB Kings, King Heavies, and King MKIIs group better at close to an inch. Predators are the very best in my TalonP, grouping under an inch and occasionally approaching 1/2 inch for 5 shots. (I prefer to shoot 10 shot groups, but not with the low capacity TalonP reservoir where accuracy can often drop a little after 5 shots.) I've tested over a dozen other pellets, and they are all less accurate than the pellets above, except my beagled-up RCBS 25 ACP slugs are also about the same accuracy as the BBTs.
After slugging my TalonP bore several times, I suspect my AirForce L-W barrel is limiting my accuracy, because the choke is very aggressive (tight). I’m beginning to wonder whether it has too much choke for optimally launching pellets too. I found that the barrel ID constricts .002″ in diameter in the last 1″ of the barrel. That seems like a awful lot of choke! (.0005 to .001 is typical, I think.) In slugging it, my TalonP barrel groove / land diameters go from .2546 / .248 down to .2525 / .246 at the choke. I measured the twist at 1:17.2, as others have reported here.
I asked Tom Gaylord about the .002" choke and he has never heard of that much choke. He said Harry Pope liked to choke a barrel a half-thousandth and one thousandth is about the most there should be.
Making the already short 12" TalonP barrel even shorter is problematic, because there is very little length extending beyond the front barrel bushing. However, I found that my choke is only .002 for the last 1/2 inch. The first part of the choke appears to have only .001" of constriction. After trying to slug short sections of barrel, I think I've determined that I can part-off the tightest section at the front of the barrel bushing (making the barrel about .56" shorter) and end up with a more reasonable .001 choke. I think it's worth a try anyway.
Given that Harry Pope's barrel were renowned for exceptional accuracy with slugs, I don't think chokes, in general, are the problem with airgun barrels. Rather, OVER-choking the barrel may be the problem!
I have a 28" TJ's 257 barrel in hand, but I need to retrieve my lathe and mill from 8 hours away before I can fit it up--hopefully before winter arrives. Reportedly the 253-51 shoots very well from that barrel and my slugs are dropping at more than 1-1/2 over the print size. Pushing a slug though my TJ's barrel shows both bands bottoming in the grooves at .257, so I'm hopeful they will work. Of course the 257-65 BBT might be better still in the TJ's barrel!
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Update: Thanks to Google, I found this German L-W page, which I've never seen before.
http://www.lothar-walther.com/163.php (http://www.lothar-walther.com/163.php)
Technical specifications:
For the highest accuracy possible, the barrel blanks come with choke, that means a narrowing of the land-groove-diameter up to 0,05 mm at the muzzle.
So my .002" choke is probably intentional and to spec (0.05mm). The German website published land and groove dimensions that match what I measured too (within my precision in measuring a slug of soft lead).
I don't think it's possible to optimally size a bullet to fit rifling that varies this much. Believe me, I've tried! I have all the NOE sizing bushings from .252 to .258 and I even used the body bushings to size the nose different from the driving band too. Driving bands of .254 or .255 and nose sizes of .252 or .253 seemed to be the best, but it doesn't make a huge difference in accuracy, which I take as evidence that no sizing combination works well with the .002" choke!
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There is one more thing you can try... Knurling from undersize for the non choked bore/groove back to non choke ~bore/ groove size
https://www.gatewaytoairguns.org/GTA/index.php?topic=119504.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=119504.0)
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Here is my "junk".
Am preverse about this...but If I'm going to buy projectiles, I'll buy pellets....if I'm going to shoot slugs, I'll cast them.
Only one ammo can of molds survived a major flood (like 12 feet of really fast moving salty water/cars/house parts. etc) 14 years ago. It got wedged under the neighbors front steps, and survived (kind of )
It happened to be my stash of "obsolete" molds....obsolete by both age and use). The mondern stuff didn't make it, being bashed-n-scattered over a long long distance.
Yeah...lemon...lemon aid...
The ammo can did leak a bit...which rusted up the outside a bit and cracked some wood handlles, but the cavities/mating faces were well greased and they survived fine (although ugly on the outside).
Saved an old Lyman electric pot too...but had to wire it all the way "on" and hook it to a "dimmer" to get it to vary temp (nd a pair of very old, EPA poison, asbestoses gloves).
(http://i157.photobucket.com/albums/t50/ribbonstone/0db755d4-87a4-48ed-ad4a-3a0b6a0f461c.jpg) (http://s157.photobucket.com/user/ribbonstone/media/0db755d4-87a4-48ed-ad4a-3a0b6a0f461c.jpg.html)
From an antique Winchester" mold, an early Hoch molds, some pretty newish T'C type molds, and some old Lyman's. BTW: that little "collor button" Lyman single cavity mold makes an excellet .45 airgun slug...and that way-old 115gr FN Winchester mold works well (once sized) for 30" / .31"s.
So fellow survivors (after all, if you are reading this, you likely survived at least one "something" that should have killed you by now), what I did was adapt my shooting to fit the ammo supply.
So...I do occasionaly clean out the pellet trips, melt the lead down (even though it's pretty soft and not all that easy to cast) and do my own "recycle". May not be airguns shooting the recycled lead all the time, but at least I deposit it off my personal property.
NOe I have a job to do...scrub 'em up (lucky the mold cavities have still survived the long storage) and grease them up once again...it's Hurricane season, and I'd like to give the suvivors a fighting chance.
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There is one more thing you can try... Knurling from undersize for the non choked bore/groove back to non choke ~bore/ groove size
https://www.gatewaytoairguns.org/GTA/index.php?topic=119504.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=119504.0)
Great suggestion, K.O.! I will certainly try it before I shorten the barrel.
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A more expensive option would be to use the TJ .25 Auto liner those BBT's were designed for. Probably not the answer you were looking for, but there have been many shooters who have had great accuracy using the TJ liner...
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I believe the barrel specification is: TJ's .25 ACP liner .250 groove, .243 land, 14" twist.
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Or try other models... Like this one ;)
http://noebulletmolds.com/smf/index.php/topic,1897.0.html (http://noebulletmolds.com/smf/index.php/topic,1897.0.html)
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A more expensive option would be to use the TJ .25 Auto liner those BBT's were designed for. Probably not the answer you were looking for, but there have been many shooters who have had great accuracy using the TJ liner...
I currently have a TJ's .257 barrel in hand, but need to fit it up. I got the TJ's 257 instead of the 25 ACP because I read so many reports of great accuracy from it--both with pellets and slugs, and even this 253-51 BBT mold that I'm using now. The reason I've tried so hard to get my 12" OEM L-W barrel to shoot accurately is I'd like to have both accurate short barrel and long 28" TJ's barrel options with the little TalonP carbine and I don't have my lathe at hand ATM to fit the TJ's barrel. The 12" OEM barrel might just have to be a Predator pellet barrel, because it's the only projectile that I've found to shoot
A more expensive option would be to use the TJ .25 Auto liner those BBT's were designed for. Probably not the answer you were looking for, but there have been many shooters who have had great accuracy using the TJ liner...
Wasn't the BBT 250-51, which reportedly drops 1-1/2 thou over print spec (driving band at .2535), made for the .25 ACP barrel? I have the slightly wider BBT 253-51 (driving band dropping at nearly .257 for me). I pushed one of my 253-51 slugs though my TJ's 257 barrel and both the lands and grooves were nicely formed or at least wiped at exactly .250 and .257, like TJ's specs it, so I have high hopes for the combination. I might still order a 257-65 BBT NOE mold for it though.
Or try other models... Like this one ;)
http://noebulletmolds.com/smf/index.php/topic,1897.0.html (http://noebulletmolds.com/smf/index.php/topic,1897.0.html)
Yes. I probably should have bought that mold instead of my RCBS 25 ACP mold, which I have to "beagle-up" with .004" of tape on both mold halves and this process I devised to eliminate finning:
http://castboolits.gunloads.com/showthread.php?336649-De-finning-A-Beagled-Mold&highlight=beagle (http://castboolits.gunloads.com/showthread.php?336649-De-finning-A-Beagled-Mold&highlight=beagle)
At the time I bought the RCBS mold, I didn't know how non-standard "25 cal." air rifle barrels could be!
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That NOE's .25 acp mold group buy is still open. It needs 10 singned before it goes to mill. So You have change to get that mold if You want.
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I have yet to see a good report with the RCBS .25 acp mold... I wonder if hogging out most of the grease groove would help...
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I have yet to see a good report with the RCBS .25 acp mold... I wonder if hogging out most of the grease groove would help...
I think for my TalonP L-W barrel the problem is the RCBS 25 ACP bullets drop at .251, which is way too small. It helped when I beagled them up, but still not great. (I'm still searching for great!)
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I have yet to see a good report with the RCBS .25 acp mold... I wonder if hogging out most of the grease groove would help...
I think for my TalonP L-W barrel the problem is the RCBS 25 ACP bullets drop at .251, which is way too small. It helped when I beagled them up, but still not great. (I'm still searching for great!)
I may have missed it, but are you sizing them to .250? Since you're using a factory barrel for now, those LW are tight! Maybe tumble lube the boolits too...
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I may have missed it, but are you sizing them to .250? Since you're using a factory barrel for now, those LW are tight! Maybe tumble lube the boolits too...
My L-W barrel slugs just about exactly as advertised on the German website (L-W's U.S. website seemingly rounds the metric dimensions to nearest thousandth of an inch.)
http://www.lothar-walther.com/163.php (http://www.lothar-walther.com/163.php)
6.29 mm lands = .2473"
6.46 mm grooves = .2543"
That's pretty big for a "25" caliber! From what I've heard, older L-W AG barrels were possibly tighter.
So sizing to .250 would, theoretically, be too small (unsized at .251 is too small from my testing and that's why I "beagled" the mold). From reading the knurling thread, .250 would be appropriate if knurling, I think, and I may try it. Sizing my BBTs down to .250 from .2565+ for knurling would be a stretch though. Maybe just a little knurling will still help with the larger diameter BBTs, however. I'd like to try to size them for the choke and then knurl them up for the larger un-choked lands and grooves.
I've been designing a simple file knurling jig in my head. I might CAD it up and 3D print it. I did some free hand file knurling and my micrometer says I'm getting mostly consistent knurls, but it could be better and I'd like to eliminate the rejects.
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Those dimensions are not at the choke, an LW barrel is about 0.002" smaller than specified at the muzzle....
Bob
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Those dimensions are not at the choke, an LW barrel is about 0.002" smaller than specified at the muzzle....
Bob
Thanks, Bob, and yes--0.002" constriction is what I too measured at my choke and what L-W publishes on their German site webpage that I linked a few posts back.
BTW, the German site does not publish the twist and the U.S. site publishes it as 1:17.7, but I measured it at 17.2, as others have also reported in these forums, FWIW.
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Those dimensions are not at the choke, an LW barrel is about 0.002" smaller than specified at the muzzle....
Bob
I reduced my TalonP bore length by 11/16". Without counter-boring the barrel, that is about all that can be removed while still using the original barrel bushing. I know I've removed the tight portion of the choke and perhaps all of it. Though it required setting-up with a 4-jaw chuck on the bore, I also cut an 11 degree crown, which reduced the bore just a smidgen more, compared to a square crown. At the short L-W barrel TalonP velocities, my 253-51-FN slugs are stable, but this barrel isn't all that accurate so I figured I had nothing to lose. Here it is before the cold blueing. Notice that the crown is recessed into the barrel bushing a bit but there's still good edge distance to the set screws.
It's supposed to snow for most of the next week and it looks like this year might be a La Nina (even worse than last year which, was near-record but was not even deemed to be a La Nina)!!! Who knows how long it will be before I can check for accuracy improvement.
I also have a 28" TJ's .257 liner in hand and a 257 65 gr. BBT mold on the way from NOE.
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I managed to find time to fire a few rounds before the snow hit. The targets were promising at 50 yards, given that I still have a few things to sort out. I think my main problem now is the BBTs are difficult to chamber. Thus, I will need a "chamber" and leade in my breech, as Bob has often advised. Even worse, the BBTs tend to cock a bit when pushing them into the breech. I loaded a few BBTs with extreme care, but a few of them still exhibited somewhat uneven rifling marks when I pushed them back out with a cleaning rod, indicating that they were slightly cocked when the first band entered the rifling. Sometimes a mark or two was even visible in the narrow area between the bands. (This is a TalonP so my finger (or a nylon push tool) was the bolt "probe.")
I think I'll clamp a diamond stone dresser in my tool post and dress a stone to the right shape with a 2 degree taper. I'll also turn a brass lap, as others have done, to finish up the "chamber" with grinding compound and polish. If this method works, I'll use it for my TJ's barrel too.
I also made some recent changes to my top hat and o-ring and I haven't set up my chronograph to find the peak of my velocity curve yet. I think the last two shots were falling off the curve here, as they went progressively higher into the 1 o'clock position. Yes--I've found that sometimes this gun shoots higher when it first starts to fall off the velocity curve, though I'm at a loss to explain the physics of it!