GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Big Bore AirGun Gate => Topic started by: mackeral5 on December 18, 2020, 01:02:00 PM
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I've had this TJ's 25-20 barrel laying around for some time now and always wanted to try it in one of my Bulldogs. It is a .500 od, 1:14 twist, a little over 27" long. One hurdle in making this happen was the desire for a barrel mounted breech oring. I have become pretty creative in using my very limited fabrication tools and skills, however cutting an internal oring groove is an operation that my hammer and chisels just aren't quite up to task for. Recently a forum member agreed to help me out with this operation, so I am now out of excuses.
The barrel is sleeved with a 11/16 OD thimble of 4130 tubing on the breech end, which mates up to 2 layers of CF tubing--a 15x13 then a 15x17. The transition from 4130 to CF occurs under the rear shroud adapter. The 4130 and CF tubing is bonded with Loctite 680.
(https://i.imgur.com/ZXzc4Ub.jpg)
(https://i.imgur.com/UkWec44.jpg)
The .257 barrel will actually end up as a swappable complete "upper" with the barrel/shroud semi-permanently attached, there is no reason to separate the 2. Here is a picture of my .357 upper and a possible shroud length. I will be installing a 17mm slip on 1/2-20 adapter once it arrives from Poland. The shroud will end up somewhere between the 2 shown. A second rear shroud adapter will be mounted at the front of the shroud, with side screws added to make the barrel/shroud one rigid unit.
(https://i.imgur.com/xkquowm.jpg)
The bulldog's design makes caliber swaps challenging, if the caliber swap system requires interchangeable bolt probes. To remove the OEM bulldog bolt, it requires almost complete disassembly, at minimum some of the trigger sear/pins must be removed to access the cocking lug/bolt. Long term, I hope to have a bolt system made very similar to the WAR style which will allow for simple caliber swaps.
I've read a lot of posts from Marco over the years where he gives advise along the lines of "build the powerplant for a .357 and put a .257 barrel on top of it." That is what we have here. The bottom end is ported .310 with full bore porting in the .257 barrel. A bolt probe is in the way, but I have tried to minimize it's size.
I've also read where it takes a lot of plenum and pressure to get .257 bullets up to speed. This experiment has taught me that there are no exceptions to physics..... Initially I tested with a regulated tube and the Huma set around 125bar. 71 gr slugs would not break 900fps, using approximately 120cc of plenum at this reg setting. I didn't invest much time here, and I may revisit this but for now I will ditch the reg.
Next I put on an unregulated tube and found a twin spring combination that worked pretty well.
Filling to 3000psi, and dialing up HST until it will just barely cock---
Hunters Supply 87gr 930fps 167fpe
Hunters Supply 71gr 1030fps 167fpe
There may be a little more in it with hammer weight, or spring, but right now I don't really see any need to push it harder.
Dialing HST back a bit gives a 4 shot string 982, 983, 984, 972 fps with Hunters Supply 71gr. Call it 4 shots of 150fpe.
I'm not quite sure where this one will end up, but I like the data I see so far. For example, when using this same barrel on my QB .257 build with a powerhouse valve, it maxed out with the 87gr at 935fps, but it took 3500psi to do so whereas the Bulldog is getting 930fps on 3000psi. I am assuming this is largely due to the Bulldog having almost double the air storage of the QB .257 build, thus maintaining a much higher average pressure during the shot. I also note the barrel was cut down approximately 1/2" when converting it fitting it to the Bulldog.
Once I get an LDC mounted I will put some lead on target. That may be a week or two while waiting on the adapter to arrive from Poland.
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I was brewing up a plan in my head last week for a .257 or .308 barrel on the Bd platform.
Outstanding work!
Thinking a longer .357 barrel could be used as well.
I did come across a .357 1:16 twist 34" long blank.
But I have no clue where to start to make the lead in.
Barrel blank was a 1" o.d.
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I was brewing up a plan in my head last week for a .257 or .308 barrel on the Bd platform.
Outstanding work!
Thinking a longer .357 barrel could be used as well.
I did come across a .357 1:16 twist 34" long blank.
But I have no clue where to start to make the lead in.
Barrel blank was a 1" o.d.
Thanks for the compliment. The chamber/lead is one of the easier parts, IMO..... search for posts about a taper pin reamer. Regarding barrel length---I wish I would have had 30+" of barrel, but all I had was a little over 27"....
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Nice work, Mike. Thx for posting. Cal changes on BD's looked very challenging to me. Glad you tackled it and provided the info for everyone. :)
Look forward to seeing that bolt set-up.
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Impressive.... It is always easier to go smaller on caliber to get big (relative) power than the other way....
Bob
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Can’t wait to see some pics of it completed. That’s some real good power . Make sure you get yourself some 257420 bullets . These barrels absolutely love them. I did something similar with the 70-35 Winchester and it was much easier to get power out of than the .257 disco. I really need to get out and shoot it some time . It’s just a bit overkill for rabbits and partridge inside 30 yards .
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This is great. I love my .257 Texan and .257 Citrus, but holy cow they are both long and front heavy. I've love a powerful bullpup in .257 for more ease in handling.
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Thanks for the encouraging words.
The Bulldog is a great all around platform. it has a sidelever, ample, versatile hammer system (105 gram OEM hammer, plenty of room for more spring/stroke, OEM hammer can be whittled down below 50 grams), over 300cc of air storage, and a .375 valve throat. There is plenty of room in the valve pocket for Cobra chambers, even adapted in a Cothran Powerhouse valve in one. At some point I may see how the Cothran works in this one.
Currently the gun is running a peek poppet from the Cobra valve I use in regulated applications, with no return spring. Initially I tested the .257 with the Cobra chamber, but I removed it for testing max FPE. An observation on Cobra valves....whether low power, or high, it seems the air spring effect drops max velocity by about 25fps. Disable the cobra chamber and velocity increases by approximately 25fps. I saw that effect with this gun. I will likely reinstall the Cobra chamber for further testing.
I have completed 2 BD barrels conversions, with a 3rd still in process--a TJ's 1:26 .357 and this TJ's .257 1:14. The third is 32" of TJ's .457 in process for another BD build. I expected the .457 to be ready by now, but sometimes things take a bit longer than expected.....
Once the muzzle adapter arrives I'll be ready to fully assemble and put rounds on paper.
Here is a random observation.... When you are used to regulated guns, shooting an unregulated big bore seems so much more extreme....I think the word violent is a fair descriptor...
Have to order more ammo. I like the 71gr from Hunter Supply but their pricing has gotten to be very unreasonable. Can anyone recommend a similar bullet/source?
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Mike ,
Are you modifying the magazines for each caliber ? I wonder if there’s someone out there that would print new ones .
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Mike ,
Are you modifying the magazines for each caliber ? I wonder if there’s someone out there that would print new ones .
Denis, I haven't modded any magazines yet, and it won't be a simple task to do a caliber conversion.
IMO the OEM mag is a good enough design and caliber swaps are so rare, I don't see it being worth anyone's while to print a mag. Darko's mags are awesome, and I know he could do it, but I don't thing it being a very profitable venture.
Something strange about the BD platform and my shooting habits----so far I have only punched paper for that I rarely use the mags.and never use the single shot trays. Someday I would like to hunt with the platform, then magazines will become more of a priority.
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A picture of the lead which was cut with a modified taper pin reamer, cut by hand, mounted in a tap handle. Later it will be polished with JB bore paste.
(https://i.imgur.com/mcnOiCI.png)
Now a pic of the modified #4 reamer. If you look closely near the pencil tip you can see where I relieved/sanded down the cutters to stop the cutting at my desired diameter.
(https://i.imgur.com/OE2wjbQ.jpg)
For those that are curious about taper pin reamers, here is a chart of sizes. For .250/.257 I chose a #4, I think because that is what I found the best price on at the time. As you see in the chart, both a #4 and a #5 could have been used. Note you can use straight or spiral flutes and both will work, however spiral flutes do a better job of not digging into the rifling.
(https://i.imgur.com/9pENnim.png)
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Did you check
gtbullets
Rimrockbullets
Western bullets
Gt has some 55 grain .257 and will be the cheapest.
Casted in .258
http://www.westernbullet.com/25caliber.html (http://www.westernbullet.com/25caliber.html)
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Did you check
gtbullets
Rimrockbullets
Western bullets
Gt has some 55 grain .257 and will be the cheapest.
Casted in .258
http://www.westernbullet.com/25caliber.html (http://www.westernbullet.com/25caliber.html)
Thanks for the suggestions
I've got some GT 55gr, which I do like, but a little light for this one. Have some of the Western 65gr in route, even though they are a tad light for my preference. Will report back on how they do.
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Has anyone been shooting a .257 in a 1-10 twist? I’m looking for advice on bullet weights.
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Has anyone been shooting a .257 in a 1-10 twist? I’m looking for advice on bullet weights.
Bob's cast bullet database is a pretty good guideline around bullet length and twist requirements as well as how a boat tail or gas check effects this relationship.
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Mike,
Thanks for the detailed pictures on the pin reamers. Looks like I need a #7 for the 357 to go with the #6 you recommended for the 30.
Am I correct that the leade would start at back of where the pellet/slug at bolt closed position? Ideally this would be just past the barrel port?
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Hi John, I can't say for certain where the lead should start ideally. But I do like to make mine start at the barrel port, as you described. I really just run the cutter in, remove, clean chips, insert preferred projectile and see how deep it seats into the chamber. Then I repeat the process until I have the depth I want. You will want to remove the cutter and clean out chips frequently and use some type of cutting oil, I just use 3 in one oil. If you don't remove chips frequently and do not go slowly, you WILL smear the rifling and it will take a lot of work to clean it up, if even possible without cutting off that section and starting over.
I may be wrong doing it this way, but with a sidelever I don't mind a shallow lead where I essentially swage the bullet into the rifling by closing the bolt. With a bolt this isn't practical. I'm sure there is a right way and a wrong way, but I'm not necessarily qualified to say which.
A shallow lead can always be cut deeper.....
Another use for the modified reamer is to modify pellet leads from a hard corner to a more gradual lead. I've done that on a .25 GM barrel, it works very well.
Sizing the reamer----I run it into the barrel until I get the right chamber diameter, by test fitting the base of a pellet/slug. Then I mark the reamer and relieve the cutters beyond the desired diameter. I relieve the cutters by chucking in a drill and spinning it against a 1" belt sander. I have one of those little Ken Onion Work Sharp units, combining it and a drill is used for many of my caveman "lathe" operations.....
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Thank you for the reamer idea and tips. I'm going to have to make one up. Very clever
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Mike,
Fantastic!
One of the best and most dependable platform out there.
Roachcreek
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The taper pin reamer idea came from various forum members talking me out of wasting a couple hundred bucks buying something that wasn't going to work for its intended job. I believe this happened across multiple threads, but here is one of them.
https://www.gatewaytoairguns.org/GTA/index.php?topic=166984.msg155874793#msg155874793 (https://www.gatewaytoairguns.org/GTA/index.php?topic=166984.msg155874793#msg155874793)
Most every DIY mod I share is based on information freely shared by others. Sometimes it's an outright plagiarism of others work, sometimes it's my own crazy idea. Some pan out others don't. I try to share both when things work and when they don't, but I don't think there is enough forum bandwidth for me to memorialize all of my mistakes and bad ideas, lol.
For a DIY hack, I think the taper pin reamers work great. If I were taking people's money for services I would probably have to invest in something with greater precision/repeatability.
RC---Thank you and I agree. A great platform. .
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I've converted this one back and forth between .257 and .357 a few times now and have a routine process to use. Both .257 and .357 bolts have been converted to slim pin style probes. At some point I hope to have a bolt with interchangeable probes made, but for now caliber changes require "dang" near full disassembly to accomplish.
The valve was replaced with a transplanted Cothran valve. This resulted in the shot cycle improving significantly due to a lighter hammer and less hammer spring, but power at 3000psi remains virtually the same with 87gr running in the 930's; 71gr 1030's; and 55gr in the 1170's. It is interesting to note that all 3 rounds max out right at 167fpe.
Hopefully the muzzle adapter arrives this week so I can finish assembly and poke some holes in a target.
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I've made reference to transplanting a Cothran valve into something other than the guns Don C designed the valve for (Marauders and 7/8 tubed gun such as Disco's and QB's.) I've held off on posting this for almost a year now, hoping someone else would share details of their adaptations. By now I would think more have done something similar, so I'll share my version....
Here are a couple of pics showing how I convert Bulldogs to a Cothran valve. I should probably say convert Cothran valves to Bulldogs.
As always, please excuse the crudeness of my work....it's not pretty, but the proof of concept is there.
(https://i.imgur.com/ANHJRTi.jpg)
(https://i.imgur.com/cPSyMh6.jpg)
(https://i.imgur.com/6MTiL6v.jpg)
The crude aluminum spacer is captive between the tube cap/adapter and the gold valve seat/carrier.
There is one modification to the Bulldog itself. The gold anodized valve seat/carrier must be opened up to allow for the larger diameter of the Cothran stem. These parts are relatively inexpensive from Crosman, I recommend any Bulldog modder to keep a spare.
A similar process can be done for many guns. The biggest challenge is the relatively large diameter of the Cothran stem, the host gun should have a throat large enough to accommodate this. Then it is just a matter of coming up with a method of mounting the balance chamber piston and adjusting stem protrusion.
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Mike,
Thx for posting those pictures and additional details. You started to take the mystery out of how you were accomplishing that, for me.
For the 257 Cothran BD tune, was that your simplified balance valve? I see delrin seat but also the pin, so wasn't sure. If so, were you able to get a bell curve like what you did with Mrod?
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Mike,
Thx for posting those pictures and additional details. You started to take the mystery out of how you were accomplishing that, for me.
For the 257 Cothran BD tune, was that your simplified balance valve? I see delrin seat but also the pin, so wasn't sure. If so, were you able to get a bell curve like what you did with Mrod?
John-
The valve has the delrin seal, however I am currently running it with the rod, in powerhouse configuration. Running it as a simplified balanced valve hasn't worked very well, at least not when going for higher energy levels. It is really easy to overdrive the hammer and bounce it off the valve body. This applies to both .257 and .357, I've tested both calibers I think I cut my stem protrusion too short as well as the piston needs to be located just tad further towards the muzzle. Another variable, I believe is barrel length. I think the combination I found for the Mrod is great at efficient, mid power tunes with short barrels. However I think the valve wants to close too soon to take advantage of a longer barrel. At least that is what I think right now.
Right now I have the .257 regulated at 150bar, a stock tube with around 50cc plenum. It does a dozen or so shots of 55gr at 945fps. This same tube/plenum combo would do 15 shots of 160fpe in .357, but with my peek poppet Cobra valve and a 125-130 bar reg setting. I may degas and convert back to the Cobra valve, I'm pretty sure it will squeeze a few more shots
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Thx, Mike. That makes sense.
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Beauty!!!
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I know it isn't quite the best use of a .257, but if it proves accurate with these 55gr HP's from GT Bullets, this may be the .257 tune I stick with for a while. Velocity seems to be pretty stable in the 945-955fps range. If it does good at 100 yards I'll do a NUAH submission with it.
This should be obvious from a math/physics perspective, but I am still amazed at how much more air is required to push .257 vs .357. This same regulator/plenum combo requires less than 130 bar to do 160fpe in .357 and here it is requiring 150 bar to do around 110fpe in .257. The .357 barrel is 2 inches longer
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With the gt bullets what kinda shot count are you getting out of .257?
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With the gt bullets what kinda shot count are you getting out of .257?
11-12 shots of 55gr in .257. 15 in .357 with 88gr.
The .357 tune took a bit of work to develop, I haven't invested near the time and effort into .257, at least not yet. For example, the current .257 tune has the hammer preloaded against the valve, if I can get the hammer in free flight there should be an improvement in efficiency.
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So if you added the pitbull 160cc extended tank.
And a regulator........what do yo think the .257 would be capable if......or without the regulator.
Say 16 shots in .257......
Secretly gathering ideas for another gun.....
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Mike ,
Can you post a link of the bullets you’re using. I’ve never heard of GT bullets and my google search is coming up empty. Maybe I’m missing something , but you should be able to get real good power from the 257 in your barrel length. ( 28” ? ) 110 FPE seems kinda week. Could it be that those bullets you’re using are either too light or maybe they are too hard requiring too much pressure to get moving ?
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Never mind the link I found the GT bullets site. It doesn’t say what lead mix they are using. I’d be willing to bet they are too hard. 40:1 lead tin or pure lead seem to work best. I’ve tried up to 20:1 and at that point the bullets were extremely hard to chamber as expected. Now I only buy the 40:1 from western metals or Rotometals.
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Never mind the link I found the GT bullets site. It doesn’t say what lead mix they are using. I’d be willing to bet they are too hard. 40:1 lead tin or pure lead seem to work best. I’ve tried up to 20:1 and at that point the bullets were extremely hard to chamber as expected. Now I only buy the 40:1 from western metals or Rotometals.
Denis- I believe the bullets are fine, I can push them ~1150fps unregulated. They chamber easily. The 110fpe is due to a relatively small plenum, I am currently testing with a regulated tube. Plenum is approximately 50-60cc IIRC. For another point of reference, in this configuration Hunters Supply 71gr only run around 850fps. Barrel length is 27.25". The comparative statements about .357 vs .257 were primarily directed towards how much more plenum pressure is required for the smaller bore.
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So if you added the pitbull 160cc extended tank.
And a regulator........what do yo think the .257 would be capable if......or without the regulator.
Say 16 shots in .257......
Secretly gathering ideas for another gun.....
I added Matt's 100cc extension, on the plenum side, increasing plenum from 50-60cc to 150-160cc. 55gr velocity went from ~950fps to 995fps. 71gr went from 850fps to 895. My hammer has been lightened down to ~82grams or so, with the OEM 105gram hammer velocities may be slightly higher. Call it 125fpe regulated at 150bar. I haven't shot a full fill to determine shot count, but I can say my tank gauge movement definitely shows greater efficiency with the larger plenum.
There's no substitute for pressure and plenum, unregulated with the full 340cc tube maxes out at 167fpe, with bullet weights of 55, 71, and 87gr.
I do have one of Matt's 160cc extensions in route, for a different project/purpose.
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I can't wait to get my BD and start experimenting!!
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The 17mm Polish muzzle adapter arrived, so it was time to assemble. Hopefully I'll get time to punch some holes in paper over the next few days.
(https://i.imgur.com/5JooDdL.jpg)
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I managed to poke some holes today, results were a bit disappointing. 2-3" groups at 80 yards.
(https://i.imgur.com/mWGB2cq.jpg)
I recall having similar issues with this barrel when I used it on a QB build. And it has had quite a few rounds through it in testing/tuning. So today I cleaned, recrowned and relapped/polished the barrel. Hopefully this will help yield more favorable results.
Of all of my TJ's barrels, this one is the roughest, even after the lapping and polishing. I do not know when this barrel was forged, I traded for it second hand. The previous owner thought it was a .25 acp barrel, however slugging and measuring twist proved it to be a 1:14 .257 barrel that TJ's refers to as a 25-20.
(https://i.imgur.com/WCDWmw5.png)
(https://i.imgur.com/uLz5AqB.png)
More to come.
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That does look pretty rough. Almost as bad as one of the B3 barrels I had a while back. It was a good pellet shooter though. Wish you luck.
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That does look pretty rough. Almost as bad as one of the B3 barrels I had a while back. It was a good pellet shooter though. Wish you luck.
Thanks Denis. I wish I would have had a borescope some time ago, when I first picked up this barrel. At the same time I must admit that I had every opportunity to use it sooner on this barrel, as in before I did any further work on it. But i didn't. Maybe it will get better, but I don't have high expectations at this point.
I will say that I have a QB78 .22 barrel that has shot multiple 1" 100 yard groups and it looks worse, lol....
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Try a proven accurate slug before beating yourself up over the barrel. Hunters Supply are not known to be accurate in air guns. These 70gr. from Nick would be worth trying in that barrel- https://nielsenspecialtyammo.com/collections/257-cal-ammo/products/70-grain-hollow-point-boat-tail-air-rifle-pellets-257-caliber-air-gun-slug-swaged?variant=12508022145117 (https://nielsenspecialtyammo.com/collections/257-cal-ammo/products/70-grain-hollow-point-boat-tail-air-rifle-pellets-257-caliber-air-gun-slug-swaged?variant=12508022145117)
If they shoot well then Arsenal makes a BT version of 258420 mold- http://arsenalmolds.com/257-Bullet-boattail (http://arsenalmolds.com/257-Bullet-boattail)
I wouldn't rule out the barrel until trying a slug better suited for it and made of soft lead.
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Try a proven accurate slug before beating yourself up over the barrel. Hunters Supply are not known to be accurate in air guns. These 70gr. from Nick would be worth trying in that barrel- https://nielsenspecialtyammo.com/collections/257-cal-ammo/products/70-grain-hollow-point-boat-tail-air-rifle-pellets-257-caliber-air-gun-slug-swaged?variant=12508022145117 (https://nielsenspecialtyammo.com/collections/257-cal-ammo/products/70-grain-hollow-point-boat-tail-air-rifle-pellets-257-caliber-air-gun-slug-swaged?variant=12508022145117)
If they shoot well then Arsenal makes a BT version of 258420 mold- http://arsenalmolds.com/257-Bullet-boattail (http://arsenalmolds.com/257-Bullet-boattail)
I wouldn't rule out the barrel until trying a slug better suited for it and made of soft lead.
Thanks for the advice. Once Nick gets his .257 tooling back up to speed I'll order some, for now they are out of stock....
I'll probably be ordering another barrel anyway, 27" is too short for .257 IMO. I have to push it too hard to build power. I will likely pick up a 32-35" in the near future.
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I went and looked back in my notes from my previous attempt at using this particular barrel. It was a QB78 conversion. I experienced similar accuracy issues but wrote it off to pushing the QB design too hard- not the best breech retention, long skinny barrel with barrel bands, etc so I abandoned the build and parted it out. I still have those parts, so there may be a reincarnation of that build at some point, albeit in a different caliber.
However, for the .257 Bulldog.....
35" of TJ's 25-20 is in route!
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Now that will be interesting.
Roachcreek
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Now that will be interesting.
Roachcreek
Hopefully in a month or so we will have some energy numbers to compare to the inline valve gun numbers. I know an inline can't be beat, but I still want to know how close the BD can get.
Then of course hopefully it will shoot MOA or better....
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And I have my original ballistic printout sheets that I printed out just before the 615 yard video, thus will be interesting. Both my .257 TJ/Haley barrels, 1-10 and 1-14, were 36 inches long.
RC
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And I have my original ballistic printout sheets that I printed out just before the 615 yard video, thus will be interesting. Both my .257 TJ/Haley barrels, 1-10 and 1-14, were 36 inches long.
RC
The blank is stuck with USPS in Cincinnati. Funny thing is the CF tubing arrived from China yesterday. The muzzle adapter is in route from Poland. Since it is 35" long I am sleeving it up to 19mm with CF. Once the blank arrives have to cut the lead/chamber then send it off for the barrel oring.
I look forward to comparing notes, hopefully I'll have this one together by maybe mid Feb? . With the current 27" barrel, and a bit more tuning I have found a consistent 5 shot, 71gr tune that goes 975, 990, 1002, 1000, 985, 970.
I haven't quite given up on the current barrel, but man, it is ROUGH.
To be very clear, unfortunately I obtained this blank second hand and do not know its history. it appeared to be brand new and unmolested, even had TJ's muzzle end label. I did not own a bore scope at the time so I never closely inspected it until much later.
Todd at TJ's recommended i lap it using a 3M polishing paper he uses, so I ordered some. It helped, but this barrel literally has craters in it. Here are pictures showing the bore's condition after quite a bit of work with 3m polishing paper and JB bore paste.
The high spots are gone, but there are still plenty of divots....
(https://i.imgur.com/9dcs6iR.jpg)
(https://i.imgur.com/wi3bqMR.jpg)
(https://i.imgur.com/T254vEg.jpg)
(https://i.imgur.com/6n20P6h.jpg)
(https://i.imgur.com/fK9JCLF.jpg)
(https://i.imgur.com/tK2qcvF.jpg)
(https://i.imgur.com/qyCcYV8.jpg)
(https://i.imgur.com/svHX1Zk.jpg)
(https://i.imgur.com/NJwR5Jl.jpg)
(https://i.imgur.com/83NOnTn.jpg)
(https://i.imgur.com/GLOU5UD.jpg)
(https://i.imgur.com/hgwTCh7.jpg)
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WOW! Those are some pits!
I’d be interested from our metallurgical oriented members on their thoughts on those.
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The barrel that came on my Ranger 45 had a interior like that. They replaced it with another TJ that while rough, did not have the craters or inclusions that the first one had. The larger .452 bore allowed me to inspect with a naked eye.
I fire lapped both the 257 barrels, I can’t say it improved accuracy that much, but it did make it easier to clean and shoot more rounds until it did need cleaning.
My Texan LSS shoots that 71 grain bullet at 1100 FPS, I polished the barrel and have not been able to get a reading on it since with the FX, which has a limit at around that velocity on what it will record. Since I polished it, it cracks now and then.
My Haley did the same thing with the 257420 bullet, I turned the psi down on my regulated tether at the time, If I remember correctly I chonied the 420 at 1134fps in the Haley. I eventually went to heavier bullets like the 80 grain NOE and 80 and 100 grain bt spitzers from Ideal and Herters molds, designed for the 257 Robert’s. The 100 grain spritzer or any 100 grain bullet never shot that well in either barrel, and the 1-10 twist never equaled the accuracy of the 1-14 barrel with bullets in the 70-80 grain range.
RC
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Great info RC. The current barrel does look a lot better after lapping with the polishing paper process Todd recommended. Accuracy seems to be a touch better but nothing worth sharing a new pic of. I have more ammo on order, but unless I start seeing improvement I don't believe I will be investing much more lead/n2 on this barrel.
I look forward to seeing what the extra 8 inches of barrel is going to do. it should be significantly better than what I have now, but not quite Texan numbers.
I greatly appreciate the info around bullet weight range and barrels.
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Still trying not to give up on this barrel.... After many many strokes of 3m polishing paper, JB bore paste, and Mother's I have most of the bore looking ok, and the craters look a lot better, but there are a couple that are just too deep to lap/polish out.
Will see how it shoots later today.
Here are a few pics after last night's efforts.
(https://i.imgur.com/KQbf7qq.jpg)
(https://i.imgur.com/rYdZPUd.jpg)
(https://i.imgur.com/ruhNGO6.jpg)
(https://i.imgur.com/t9e8FLY.jpg)
(https://i.imgur.com/hJBuDtO.jpg)
(https://i.imgur.com/ATZRVFu.jpg)
(https://i.imgur.com/iI9j9FW.jpg)
(https://i.imgur.com/GqECEPj.jpg)
(https://i.imgur.com/CkPxlFN.jpg)
Those are the bad spots, the rest of the bore looks more like this.
(https://i.imgur.com/YsAXqer.jpg)
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Still no bueno. A few shots look promising then fliers. The bad spots collect lead very quickly.
(https://i.imgur.com/Rk0CP0O.png)
(https://i.imgur.com/St4tWA2.png)
The spots are throughout the barrel's length, there's not even enough continuous clean barrel to make a pistol barrel out of.
Another lesson learned, always use the borescope before investing more time and $$$ on a barrel blank.
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I decided to dissect the last 12" or so on the muzzle end. Note this is after hundreds of strokes with 3m polishing cloth and JB bore paste.
(https://i.imgur.com/9H5p6G8.jpg)
(https://i.imgur.com/dqRyh38.jpg)
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Probably splitting that barrel was the best thing for it. :(
RC
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Probably splitting that barrel was the best thing for it. :(
RC
I hated to give up on it, but it felt pretty good.
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Long .257 barrel making progress. MAYBE some chrono numbers next week....
(https://i.imgur.com/r5iHKGu.jpg)
35.5" barrel, 42" overall length.
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I love it. I know many will disagree on how 42 inches can be sleek but it sure is. I really don’t remember the length of my Haley 257 with the 36 inch barrels plus flash hider. I did not refer to it as being sleek. ;D
Well done,
Roachcreek
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Great build. I’m certain that you will have better success with that barrel and length. Maybe I missed it but are you going to use a barrel band or free float this one?
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Great build. I’m certain that you will have better success with that barrel and length. Maybe I missed it but are you going to use a barrel band or free float this one?
Thanks Denis.
The barrel is being sleeved to 19mm with CF. it will have a semi-permanently attached cut down bulldog shroud.
The gun is designed to quick change between .357 and .257. Bolt probes will swap like the system used in the old WAR guns, a threaded stud that the caliber specific probe screws onto. The barrel/shroud/scope assembly and bolt probe will be caliber specific. In theory, a simple adjustment of the HST will allow for caliber changes, with very little if any re-zeroing required.
The .257 upper will start out with something more like this:
(https://i.imgur.com/5JooDdL.jpg)
If barrel harmonics and droop will allow it I will end up with something like this.
(https://i.imgur.com/6xhLF49.jpg)
this is my .357 upper for the same gun. it is a 29" TJ's 1:26, 1/2 OD sleeved up to 19mm with a Clague reflex moderator. The gun maxes out over 350fpe and will do a 50 shot tune of 300+fpe with this upper.
In .257 I am hopeful of a 150-175fpe tune but with a very nice, docile shot cycle. If it will shoot these MP .257-640 HP's (drop at 68gr) upwards of 1050fps and do it somewhat efficiently AND accurately I will be happy.
Here is a pic of the MP 257-640 GC molded as hollowpoint along with a 257420 boat tail for comparison. The .257-640 mold also comes with pins for a heavier penta style hollow point as well as a flat point. I haven't molded anything but the deep hollowpoints so far.
(https://i.imgur.com/sEqqwzU.jpg)
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I love it. I know many will disagree on how 42 inches can be sleek but it sure is. I really don’t remember the length of my Haley 257 with the 36 inch barrels plus flash hider. I did not refer to it as being sleek. ;D
Well done,
Roachcreek
Thanks RC. Slowly coming together. Hopefully it does better than the previous barrel.
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Correction on the 257-640 mold. i does NOT come with a penta hollowpoint pin.
The 3 pins are deep hollowpoint, dimple, and flat nose.
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Long .257 barrel making progress. MAYBE some chrono numbers next week....
(https://i.imgur.com/r5iHKGu.jpg)
35.5" barrel, 42" overall length.
Now this makes me wonder how my .257 brod will look like with its 36" barrel... My guess silly.
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Long .257 barrel making progress. MAYBE some chrono numbers next week....
(https://i.imgur.com/r5iHKGu.jpg)
35.5" barrel, 42" overall length.
Now this makes me wonder how my .257 brod will look like with its 36" barrel... My guess silly.
Not silly, just LOOONNGGG.... you will need to help the breech out however you can, it may want to flex in the mag slot..
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I will likely have support the barrel some how to help with that. I plane on single shot tray so maybe some sort or top rail that dont interfere with loading and the scope.
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Whew! That is really coming along! Even though it's long, I bet it handles far better than a conventional rifle would, with the same length barrel!
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Things are moving pretty slow, but I did manage to rough in the barrel port and barrel screw indentions. Barrel port is at .200 and slightly elongated to approximately .250 long. I still plan to take it to .300 but doing this all by hand requires me to do it in stages, and only doing it when it feels "right."
This meant that the barrel is now secure and the air passage is clear so hey, why not send a few rounds into the trap?
All I have is 3200psi of nitrogen, so that's as high as I tested. Here are some quick max velocity numbers.
With MP 257-640 HP's dropping at 68gr max velocity 1125fps 191fpe
With some 257420 boat tails from Apex, weighing in at 71gr, max velocity 1075fps. 182fpe
A regulated tune is intriguing to me. A bit of testing found that it will send the 68gr 985fps on a miserly 2300psi. Of course this is with a 340cc tube as a plenum. later today I will assemble with 160cc of plenum and 340cc HPA storage and see how many of these 145fpe shots I can wring out of it.
That long 35.5" barrel makes a BIG difference. Once i swap out tanks we can see what kind of numbers 3500psi will produce.
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How long of a projectile can a BD mag hold again?
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The wheel measures .675 thick.
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The wheel measures .675 thick.
Hmmmmm...
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...
All I have is 3200psi of nitrogen, so that's as high as I tested. Here are some quick max velocity numbers.
...
With some 257420 boat tails from Apex, weighing in at 71gr, max velocity 1075fps. 182fpe
...
My Armada has a 36" TJ 25-20 liner and with 73gr RL 257420 slugs at 3200psi, averaging 1058fps, 181fpe
So seems about right.
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...
All I have is 3200psi of nitrogen, so that's as high as I tested. Here are some quick max velocity numbers.
...
With some 257420 boat tails from Apex, weighing in at 71gr, max velocity 1075fps. 182fpe
...
My Armada has a 36" TJ 25-20 liner and with 73gr RL 257420 slugs at 3200psi, averaging 1058fps, 181fpe
So seems about right.
Yes, very similar results between the very similar barrels. Big difference in powerplants though.. Mine is old school PCP. ~102 gram hammer and stiff spring, ~.400 peek poppet on a .375 throat. Multi-caliber gun, .257 and .357.
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I would say you need a barrel band when you proceed to accuracy testing stage. CF sleeving might also be a good idea. With the power you have there I'd also try 257388 bullets.
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I would say you need a barrel band when you proceed to accuracy testing stage. CF sleeving might also be a good idea. With the power you have there I'd also try 257388 bullets.
Agreed on the sleeving and barrel band. Read a few posts up, the pic with the barrel hanging in the wind was merely a mock-up... It has now been sleeved to 19mm with CF, and will be supported forward of the breech.
Thanks for the recommendation on bullets to try. for now I have a 65-75gr assortment of cast and swaged from the various manufacturers. I'm not sure I will ultimately run it hard enough for heavier ammo. But, in the early phases it is fun to see how much energy it can produce.
My only mold is the MP 257-640 GC. In deep hollowpoint it drops at 68gr, flat point 72gr. I hope it proves to be accurate.
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I would say you need a barrel band when you proceed to accuracy testing stage. CF sleeving might also be a good idea. With the power you have there I'd also try 257388 bullets.
Agreed on the sleeving and barrel band. Read a few posts up, the pic with the barrel hanging in the wind was merely a mock-up... It has now been sleeved to 19mm with CF, and will be supported forward of the breech.
Thanks for the recommendation on bullets to try. for now I have a 65-75gr assortment of cast and swaged from the various manufacturers. I'm not sure I will ultimately run it hard enough for heavier ammo. But, in the early phases it is fun to see how much energy it can produce.
My only mold is the MP 257-640 GC. In deep hollowpoint it drops at 68gr, flat point 72gr. I hope it proves to be accurate.
Well those 257420s seem a bit fast to me, I wouldn't go over 1050 fps. 257388 mold is available from Arsenal and drops around 85 grains. That should be around 1000 fps with your setup which to me sounds quite perfect. I was shooting them at 920 fps and I got a feeling that a bit more speed would have helped. Arsenal also has BT version of 257420 but that likes a bit lower speed, they are very accurate at 920 fps from my Evanix and groups start to open up with more speed.
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I would say you need a barrel band when you proceed to accuracy testing stage. CF sleeving might also be a good idea. With the power you have there I'd also try 257388 bullets.
Agreed on the sleeving and barrel band. Read a few posts up, the pic with the barrel hanging in the wind was merely a mock-up... It has now been sleeved to 19mm with CF, and will be supported forward of the breech.
Thanks for the recommendation on bullets to try. for now I have a 65-75gr assortment of cast and swaged from the various manufacturers. I'm not sure I will ultimately run it hard enough for heavier ammo. But, in the early phases it is fun to see how much energy it can produce.
My only mold is the MP 257-640 GC. In deep hollowpoint it drops at 68gr, flat point 72gr. I hope it proves to be accurate.
Well those 257420s seem a bit fast to me, I wouldn't go over 1050 fps. 257388 mold is available from Arsenal and drops around 85 grains. That should be around 1000 fps with your setup which to me sounds quite perfect. I was shooting them at 920 fps and I got a feeling that a bit more speed would have helped. Arsenal also has BT version of 257420 but that likes a bit lower speed, they are very accurate at 920 fps from my Evanix and groups start to open up with more speed.
That's great feedback, thanks for sharing your experience. What you've done with the Evanix is very impressive.
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Here is another mock-up. it is a functioning gun at this point, however with a few temporary parts. The bolt probe is cobbled together and the shroud supports are roughly machined. An caliber swappable, interchangeable probe bolt system and a set of precisely machined barrel supports are in USPS possession. Hopefully I'll have those parts this week.
Barrel is sleeved in 19mm CF, tube is equipped with Matt's 160cc extension bringing air capacity to ~500cc.
I forgot to install my depinger, will add it when it comes time to replace the bolt/probe system.
A DonnyFL KOI does a surprising job of making the 165fpe bark a little more tame. Not backyard friendly, but still quieter than the PINGGGGGG!
Total length is 48" with the KOI.
(https://i.imgur.com/CyOKFyU.jpg)
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During lunch I was able to shoot a few initial groups using freshly cast MP Molds 257-640's, cast with the deep hollow point pins. The batch used for this testing dropped at 68.7-68.8gr and were sized at .257. At this stage I've cast probably 300ish bullets of various molds and probably melted down half of those, so I have a long ways to go in learning proper technique, etc. I lubed with 10wt silicon RC shock oil.
(https://i.imgur.com/3V9cOF5.jpg)
This mold was a bit of a gamble as it isn't the most popular, I only found one reference to it on the airgun forums, but no real performance data. I liked the fairly large flat point/hollowoint and it didn't appear to have much surface area of contact with the bore, so I rolled the dice.
Here is a target with groups of 5 shots. The center bull was the sighter. Shots were taken at 75 yards, all the distance I have setup right now,
(https://i.imgur.com/NSubG9z.jpg)
These shots were shot standing with the pressure tube resting on a Tack Driver bag. Not a bad start, especially considering all of the variables at play. I did notice the long barrel requires more careful follow-through.
The current tune is 7 shots 1023, 1044, 1049, 1052, 1045, 1042, 1028fps, a 7 shot average of 1040fps, 165fpe. 3100psi fill. It uses about 500 psi of air.
I am enjoying casting my own ammo, thanks to all the guys that freely share their experience i was able to get off to a bit less shaky of a start than anticipated.
I expect groups to tighten up as I get more experience with this long barrel and better at casting. Also, the barrel isn't fully secured in the shroud, I have some additional parts arriving hopefully this week which should further stabilize the barrel.
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You must be ecstatic of the results, I know I would be with groups like that from an untested mold, untested rifle , and only sizing once. Very promising indeed. Looking forward to see some more. Glad to see this barrel is a performer.
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You must be ecstatic of the results, I know I would be with groups like that from an untested mold, untested rifle , and only sizing once. Very promising indeed. Looking forward to see some more. Glad to see this barrel is a performer.
Yes sir indeed. I don't feel quite as bad about splitting that other barrel down the middle now that things are going in the right direction.
There are a lot of personal "firsts" going on with this one.. After watching one of Sean Perro's vidieos I created my first lead lap for this barrel. I ended up swapping ends from the way it was labeled as the end labeled muzzle felt more loose to me when I slugged prior to lead lapping. Also, there were more inclusions towards the end labeled as the muzzle. So I rolled the dice and swapped ends. It was a gamble, but so far it appears to have paid off.....
One thing I noticed about these .257 TJ's barrels---they are not as close to "perfect" as my .357's and .300's. Even after a thorough lap job, there are still some spots in it that I am not happy with.....
I am really happy with the performance untethered with a 3100psi fill. But, with 500cc of air and 35.5" of barrel I guess it shouldn't be surprising...
More to come. Working on getting a mag to function....
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Great work Mike, really satisfying isn’t it. Imagine what it will do with bullets sorted to specific weights and tethered.
I am just tickled your doing that, it will only get better.
Regards,
Roachcreek
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That's some work to be proud of right there. If you regulated it those groups will likely tighten up even further. Fine job Sir!
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Congratulations, it's a start of a long road but a good start. At the end you'll have very accurate long range airgun that shoots bullets with good BC from magazine. It sounds like the Buldog has many things going for it like the long magazine and possibility to use extra long barrel. I forgot to mention, those 257420 BTs measure 0.18 BC and 257388s should have 0.2 BC. That's about the best bullets we can get up to speed with 3000ish psi.
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Great work Mike, really satisfying isn’t it. Imagine what it will do with bullets sorted to specific weights and tethered.
I am just tickled your doing that, it will only get better.
Regards,
Roachcreek
Thanks RC for your words of encouragement as well as well as your experience. It is pretty neat to see it starting to come together. No doubt a communal effort, so many different people's experiences have contributed to the process. Several forum members also contributed their skills/services on specific parts/pieces.
More to come.
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Congratulations, it's a start of a long road but a good start. At the end you'll have very accurate long range airgun that shoots bullets with good BC from magazine. It sounds like the Buldog has many things going for it like the long magazine and possibility to use extra long barrel. I forgot to mention, those 257420 BTs measure 0.18 BC and 257388s should have 0.2 BC. That's about the best bullets we can get up to speed with 3000ish psi.
Thanks for the kind words and encouragement. I really appreciate the bullet info, that 257388 will probably be next mold.
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That's some work to be proud of right there. If you regulated it those groups will likely tighten up even further. Fine job Sir!
So far regulated testing has not been very encouraging, at least not with 3000 psi fills. Not enough headroom to have decent shot count. As time goes on I plan to do further regulated testing.
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Fantastic job so far Mackeral5! Absolutely fantastic! I hope those trigger parts come in, if they haven't already!
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Fantastic job so far Mackeral5! Absolutely fantastic! I hope those trigger parts come in, if they haven't already!
Thanks Tom. They should arrive Thursday. I probably will not use them anytime soon, will sit them aside for a while...
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Over lunch today I put a target at my longest range--102 yards. Same MP 257-640's sized .257, sorted at 68-7-68.8gr. Running approximately 1040-1050fps.
Bottom right group was the first group, aiming at the upper right bull, 7 shots from a 3100psi fill. Made a scope adjustment and shot the middle group, albeit a little more hurried with less care in follow-through. Made another slight scope adjustment, then filled to 3000psi and put 5 shots in the vicinity of the upper right bull while being a bit more thoughtful in follow-through.
(https://i.imgur.com/YxgWwtW.jpg)
Not too shabby for groups 6-8 out of a new DIY contraption gun...
This gun was designed to quick change calibers (.257 and .357) by unscrewing bolt probes (copied the old WAR design) and changing the barrel/shroud/scope as a complete upper assembly. I don't know if I'll be swapping back to .357 on this one, may just have to build another bulldog for the .357 upper, lol...
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Mike,
Well done.
Roachcreek
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Mike,
Well done.
Roachcreek
Thanks RC... Working on a regulated tune that is showing promise, only around 155fpe but does seem to be fairly accurate.
running low on nitrogen... Went to swap tanks, vendor is out until Tuesday.
I needed to change my wife's vehicle's front pads/rotors this weekend anyway, lol.
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I was finally able to swap out my tank and do some higher pressure testing. I got frustrated with the regulated testing. A shot from a 160cc plenum and then expecting a Huma to refill said plenum is new territory for me. At some point I will revisit the regulated testing, but for now I need to take a break. I think I am missing something. So, back to unregulated. I swapped tubes to the long (500cc) tube designed for higher pressures.
I also converted probes over to the interchangeable caliber/probe bolt system that Matt/Luge007 and I designed and Matt then fabricated. I did some work to the lead, moved it forward a bit. Next I plan to firelap the barrel...
This pic is prior to trimming pin probes to length.
(https://i.imgur.com/Zo1rpSa.jpg)
(https://i.imgur.com/ODYmJFK.jpg)
(https://i.imgur.com/P44RodJ.jpg)
Filling to 3500psi and cranking on the HST to max (pitbull spring) pushes 88gr "Lovern" bullets to 1120fps max. 245fpe!!!
I have Arsenal's 85gr mold on order, I hope to receive it in upcoming weeks.
I am likely to build a 35" .357 barrel so I can swap calibers without having to swap tubes to the short tube.
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I'm VERY happy to see that the WAR probe design worked out in your BD!!
Perhaps in the far-flung future, a bottled design (similar to a Maverick) might pair well w/your build?
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You need to get yourself an Aqua Environment tethering regulator. Huma just can't keep up with higher power levels, been there done that bought Aqua Environment. One of these things below but you can get the regulating unit from manufacturer and add the gauges and other pieces and save some money.
https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/ (https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/)
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You need to get yourself an Aqua Environment tethering regulator. Huma just can't keep up with higher power levels, been there done that bought Aqua Environment. One of these things below but you can get the regulating unit from manufacturer and add the gauges and other pieces and save some money.
https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/ (https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/)
Understood. Tethered to a regulated tank and building a regulated gun are 2 different setups.... There is a desire to have a self contained, regulated tube as well as an unregulated tube that can be tethered.
I'm good on the tethered setup...
(https://i.imgur.com/dVqpxcd.jpg)
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Geo Schoonmaker designed a printed a .257 magazine wheel. He did a phenomenal job. Awesome guy to work with.
I added an aluminum shim (approx .050") to the stop post in the magazine body to take up the difference between .357 and .257. After a bit of fiddling I believe it is functioning very well. In upcoming days I will test for accuracy.
(https://i.imgur.com/P6bOaLF.jpg)
(https://i.imgur.com/CKH5hbB.jpg)
(https://i.imgur.com/OwAPOr8.jpg)
(https://i.imgur.com/tdvkFX2.jpg)
Note the slot I carved in the rear cover is unrelated to Geo's design, this is to accommodate my longish bolt pin probe...
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You need to get yourself an Aqua Environment tethering regulator. Huma just can't keep up with higher power levels, been there done that bought Aqua Environment. One of these things below but you can get the regulating unit from manufacturer and add the gauges and other pieces and save some money.
https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/ (https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/)
Understood. Tethered to a regulated tank and building a regulated gun are 2 different setups.... There is a desire to have a self contained, regulated tube as well as an unregulated tube that can be tethered.
I'm good on the tethered setup...
(https://i.imgur.com/dVqpxcd.jpg)
Oh, you got one already. I had HUMA tethering reg and it had trouble keeping up at 150 fpe even when modded according to Huub's instructions. Those internal regs are usually even slower so I don't think there are any neat solutions.
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You need to get yourself an Aqua Environment tethering regulator. Huma just can't keep up with higher power levels, been there done that bought Aqua Environment. One of these things below but you can get the regulating unit from manufacturer and add the gauges and other pieces and save some money.
https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/ (https://www.bestfittings.co.uk/shop/airgun-charging-equipment/cylinder-accessories/7000-pressure-regulator-kit-for-nitrogen-high-pressure-air/)
Understood. Tethered to a regulated tank and building a regulated gun are 2 different setups.... There is a desire to have a self contained, regulated tube as well as an unregulated tube that can be tethered.
I'm good on the tethered setup...
(https://i.imgur.com/dVqpxcd.jpg)
Oh, you got one already. I had HUMA tethering reg and it had trouble keeping up at 150 fpe even when modded according to Huub's instructions. Those internal regs are usually even slower so I don't think there are any neat solutions.
The regulator and a Joe B Guppie was my first major purchase down the rabbit hole, long before I had any real pcp experience. The journey has become deeper and deeper ever since.
Thanks for continuing to share your experience. Interesting to hear the Huma tethering reg didn't work well with high energy/volume. What type of mods did Huub recommend?
I think my current regulated frustrations are around the fact that I made the poppet stem too short and the hammer is bouncing off the valve at lower pressures. Once the frustration wanes I'll get back to it.
Then when that problem is resolved then the whole refresh rate issue will come into play. I considered installing a street L in my gauge port so I could watch the plenum refresh between shots....
I can't wait for the Arsenal 85gr mold to arrive....
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Huub told me to open up some airpaths inside the regulator a bit. Since mine was tethering regulator and yours is internal I would suggest you to contact Huub and ask about flow improvements that you can do, he's a very helpful guy.
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Huub told me to open up some airpaths inside the regulator a bit. Since mine was tethering regulator and yours is internal I would suggest you to contact Huub and ask about flow improvements that you can do, he's a very helpful guy.
Thanks for the info. I am working on a longer stemmed poppet, once it stops bouncing the hammer off the valve nut we can move onto the next problem, which may or may not be plenum refresh rate....
After adjusting the probe pin/lead area I've seen a steady 72gr 1030fps at 2600psi. But this is with a 500cc tube vs. a 160cc regulated plenum...
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After a lot of frustration I have a decent regulated tune that appears to be stable. This batch of slugs weighs 69.3-4gr. 15 shots averaging 970fps from 3500 to 2500psi. The Huma is maxed out, this is all it's got in regulated form, with a 160cc plenum shooting .257.
The Huma's refresh rate seems to be fine, after I remembered the restrictor screw, which has now been removed. It has no problems refreshing a 160cc plenum in 15-20 seconds between shots.
The gun is creeping up on good accuracy. After a full fill, a string of 15 shots, fired very quickly at 50 yards gave this group.
(https://i.imgur.com/9z8B5kn.jpg)
Then stretched out to 102 yards targets are beginning to look like this. The lower target is the sighter, then 5 shot groups on the upper target.
(https://i.imgur.com/N6KLEu8.jpg)
I recently picked up one of UTG's Over-Bore bipods, it is amazing how much easier it is to shoot with. I highly recommend to anyone trying to shoot long range with the Bulldog or any other tippy/top heavy platform.
(https://i.imgur.com/a3COzh7.jpg)
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One more group, this time 5 shots from the magazine. Top left bull.
(https://i.imgur.com/f5QSVlL.jpg)
Geo's mag wheel does not negatively impact accuracy, I don't think.
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Nice shooting Mike. Thats acceptable grouping in my book. Have you been trying different size bullets or shooting as cast?
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Nice shooting Mike. Thats acceptable grouping in my book. Have you been trying different size bullets or shooting as cast?
Thanks Denis.. After casting I run them through a .257 sizer just for consistency. Then I sort by weight. .257 seems to have good engraving. I think I have a .256 die that I could test with, I need to look through my stuff.
I haven't polished the barrel yet---the current finish is at the state of a 600grit fire lapping. I need to get after it with the JB's and then Mothers. These groups are with probably 150ish rounds through the barrel. I may clean and polish today to see how that effects groups.
I did finish off the targets, these groups were shot randomly across 2 days.
(https://i.imgur.com/wRZATNQ.jpg)
The groups so far just look to me like I am the primary source of variation.
Funny thing about these builds. There are so many variables...Did I correctly modify the taper pin reamer then is my hand cut lead parallel and centered to the bore? Is my crown good? Are bullets passing cleanly over the barrel port? Is my probe loading slugs straight? Is there any problem with my home made peek poppet, stem and cobra valve? Is my slip on muzzle adapter imparting bad harmonics on the barrel? Do I need to better secure the barrel to shroud? My hammer system, is it consistent? Then to the bullets---I've only been casting a short time. I really don't visually inspect my bullets--I size and weigh them. Each casting session yields slightly different average weights. I do cull those that are greater than 1 gr lighter or heavier than the average weights.
Anyway, I'm glad it is performing decently right now. I hope to be able to find some sub 1 inch groups. If I can achieve that repeatedly it will be time to pack up and go to a friends place and stretch the distance out to 200 yards or so...
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After a 2 year hiatus I decided to dust this one off. It had been scattered across my bench for well over a year.
I never was quite happy with the .257. Huge 36" barrel....it took a ton of air to get 70gr .257 ammo up to speed. It was fun to generate well over 200fpe when maxing everything out, but being the Bulldog is not bottled, there is only so much air you can cram into a tube..... If I have to shoot tethered and/or live with low shot counts, I am going to enjoy the ergonomics of a RIFLE vs the tippiness of a bullpup......
It took me buying over 60 inches of TJ's 1:14 to figure all of this out, lol.....
Through this process I learned that I prefer a bulldog with OEM length tubes. Most of my shooting is punching paper, for that I want a nice flat regulated shot string. This applies to any caliber. In .357 I have a nice 15 shot 160fpe tune that has demonstrated <1.5moa accuracy, and very repeatable.
I recently made up a 700mm STX Superior Heavy liner in .25. Using "in stock" materials, It took 4 layers of CF tubing to get to the 19mm OD my shrouds/adapters are configured for. In the end this DIY effort cost a little over $300....I will not be doing this again. For a little more I could have purchased a quality barrel from a reputable airgunsmith. But, DIY is part of the satisfaction for me, or in some cases contributes to disappointment. We will see where this one ends up. In upcoming days/weeks I will work on casting up some more MPMolds 6.35 airgun bullets. Hopefully it will shoot straight.
The gun is ported huge, .328, as it was originally intended for .357. Valvetrain is my version of adapting a Cothran Powerhouse valve into the Bulldog, but with the poppet configured more like a "simplified balanced valve" as outlined in Bob's Workshop. The valve is knocked open by a very whittled-upon OEM hammer, weighing in at 43grams, propelled by an SSG with the hammer in free flight.
By swapping barrels and probes back to the 755mm TJ's 1:26 .357 barrel, refilling, and making no other changes we get 12 shots of GT Bullets 88gr at 950fps. Note the 15 shot 160fpe tune mentioned above is at a lower reg set point.
It takes about the same amount of air to generate 90fpe in .250 as it does to generate 170fpe in .357.
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I've done some following on this build. I've really wanted a .257 bulldog just haven't had the time. Let me know if you want to part with the .257 stuff.
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I've done some following on this build. I've really wanted a .257 bulldog just haven't had the time. Let me know if you want to part with the .257 stuff.
Thanks for the note. I will likely never sell the barrel drop in ready for a Bulldog, the work was more proof of concept and not executed at a level that I would feel comfortable passing on to some one else...
Even after dropping down to .250 and <50gr slugs I am seeing that there is only so far one scan stretch the Bulldog's hpa storage..... .25 doing >75fpe burns a significant amount of hpa. Approx 340 cc only goes so far no matter how you slice/tune it.
I am beginning to realize that if I am going to ever be happy with decent energy levels in .25, it will likely have to be bottle fed.....
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After 2 years of being scattered across my bench I finally reassembled this particular bulldog in its clamshell stock.
My slug testing was an absolute failure. I never even produced a pattern. MP Molds 6.35 Airgun bullets at 48.3gr running 890fps, MP Molds 44gr hollowpoints running 905fps, both were shotgunning out of the 700MM STX Superior Heavy.
Just to determine what was going on--was it the gun, the shooter, the ammo?? I put some King Heavies on paper at 100 yards. They were running pretty hot, around 1030fps and based on all of the reading I've done they are less than ideal in the STX Superior Heavy liners. However they shot very well. Much like my experience with the 600mm STX Superior standard in my Brod, this combination will cut a nice clean hole for a few shots if the shooter does their part.
After a bit more testing/tuning different SSG, hammer weight, balance valve combinations I settled in on a 1000fps King Heavy tune. It seems to get right around 20 shots of this tune before falling off regulator.
The best group was my first group, just low of the center bull. I made a scope adjustment then shot the rest. The group around the top left bull was shots 21-25 of a full fill, well off reg. After shooting that group I realized that I forgot to install the rubber butt pad, I'm sure that didn't help matters any.
(https://i.imgur.com/iT5c7TN.jpg)
(https://i.imgur.com/UsBmc9r.jpg)
I have some Altaros slugs on order so I can at least see how it does with good ammo. As far as my cast slugs producing dismal results, I may or may not revisit that any time soon. Casting is a cooler weather activity for me, and now summer is upon as and temps are rising into the high 80's, soon into the 90's.
It had been a couple years since I previously shot a bulldog at distance. I have to say it is far from a pleasant gun to shoot. The action is loud, a bit on the violent side. Having a 43gram hammer in free flight doesn't help. I had totally forgotten how freaking loud the clamshell stocks are. I even went as far as to coat the inside of this one with Dynamat
Hopefully the Altaros slugs yield good results, but even if they do, I sense we are nearing the end of our journey with this platform.
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Shortly after making the previous post I decided to attempt and make the bulldog a bit more pleasant to shoot. One of my primary complaints was the loudness of the hammer strike right at my ear when shooting, even with a peek striker. I decided to uses available materials and make up an MDS hammer. All I had was 1/2" brass rod for the inner core, which needed a .350 counterbore for my SSG's spring guide. I drilled/tapped the front of the brass core 1/4-28 and made up a protruding peek striker to mimic the OEM hammer design. care was taken in critical areas, not so much in non-critical areas. As most everything else that is carved out with my caveman tools, it is nothing pretty. But it works.
(https://i.imgur.com/NbukJgP.jpg)
(https://i.imgur.com/QqsdGdR.jpg)
(https://i.imgur.com/uYwSkG7.jpg)
As seen here, it only weighs 31.5grams. I am working with a machinist friend to create a design with a larger brass core, hoping to achieve at minimum a 40 gram hammer.
This did indeed make the gun more pleasant to shoot.
The Altaros slugs arrived last week. They weighed in right at 49.5 gr. This is convenient as I was able to use the MP 48.3gr for chronograph testing, the Altaros shoots at very similar velocity.
I must say, the Altaros slugs did not disappoint. Using the same tune as above, which resulted in King Heavies running around 1030fps, the Altaros were running 845-850fps. Point of impact was a little under 2 inches lower than the King Heavies at 100 yards.
Initial groups with the Altaros slugs looked like this:
(https://i.imgur.com/lGVmdDx.jpg)
I couldn't help but swap to my unregulated high pressure tube and do some max power testing. Before I type the results, I must remind everyone this gun is ported huge for .357, as in .328 to the barrel. My grafting in of the Superior Heavy liner used the big FX Huma slug transfer port, which is of very similar size to the gun's existing .328 porting.
(https://i.imgur.com/jJMmsqH.png)
This bulldog's bolt linkage has been tweaked a bit to allow for max over-camming, which in turn allows for significant bolt retraction. All of this adds up to huge porting for a .250.
For unregulated max-effort testing I replaced the MDS hammer with a slightly lightened OEM hammer weighing in at 84 grams, with the hammer propelled by the same SSG used with the MDS hammer.
While I expected some decent numbers at 3500psi, I was a bit shocked by the first shot across the chronograph. 1178fps with the MP 48.3gr. a few more shots backed that up. I dialed in a bit more hammer free flight and was able to produce a 10 shot tune of roughly 1080-1105-1075fps. Amazingly, at 3000psi, the Altaros 49.5gr slugs were still running over 1090fps.
I spent some time playing with unregulated tunes and found several 90-110fpe tunes with 25-30 shots over a 30-40fps ES. Along the way I reduced the vent size in my balanced valve to help flatten the low pressure side of the bell curve. This was all fun and interesting data collection, but really not what my intentions are for this gun. At the end of the day, my goals for this build are accuracy and precision, so back to regulated we will go....
So, all in all, I did manage to become more enthusiastic about this platform by adding the mds hammer, going to the STX Superior Heavy liner, and updating my balanced valve to the most recent state of the Simplified Balanced Valve collaboration/thread. Here are some valve pics, which I previously shared in a separate thread. The design is based on using a piston and poppet from a Cothran valve, the poppet receiving a few modifications such as a delrin seal.
(https://i.imgur.com/BWZKYEm.png)
(https://i.imgur.com/ndhrN0W.png)
(https://i.imgur.com/a5vZuIn.png)
(https://i.imgur.com/eajnoQK.png)
A bit of damage from the valve development process:
(https://i.imgur.com/jFC9UPK.png)
(https://i.imgur.com/15vwq33.png)