.25 cal 51 gr. NOE Bob's Boattails

[rsterne]

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....






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....



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

[scottyhazzard]

Excellent write up and guide. I look forward to reading how they shoot.

[rsterne]

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

[Hobbyman2007]

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.

[rsterne]

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

[deadguy]

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.

[tnt76]

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.

[rsterne]

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....



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....




and here are the recovered bullets.... The FN expanded to larger than bore size.... The HP expanded well, with the nose portion coming apart....





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

[rsterne]

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

[deadguy]

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.

[K.O.]

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...

[rsterne]

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

[deadguy]

So how can the chamber be fixed? Do I need to live with using a tool to load, or consider getting a new barrel?

[K.O.]

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...

[rsterne]

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

[K.O.]

oops meant groove size edited my above post

[25ACP]

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.

[rsterne]

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

If you have any questions, just ask, or PM me on either this Forum or the NOE Forum....

Bob

[25ACP]

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?

[25ACP]

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