Big Bore Pistol Build

[rsterne]

Make those cans dance !!!



Exit hole on soup can, with entrance hole visible on the other side.... This thing sure packs a whallop !!!

Bob

[Monkeydad1969]

I find this study FASCINATING!!!!! It has me thinking in ten different directions all at once. I'm thinking how much FPE and FPS I could muster out of a 2400KT in .22. And with a b&a .25 barrel.  But being new to the co2 version of things, I didn't want to sound pretty dumb.   

I have a B&A .25 barrel (1/2"OD).  It is very accurate, I haven't even put 500 pellets thru it yet, but it will hit the same hole.

Joe

[Jobobo]

This seems super cool that it is possible. I think many of us are Ameriacn and are annoyed at Canada's limits. I would still love one in my stable.

[rsterne]

You can do all the same mods no matter which side of the 49th you live on.... I happen to think that 500ish fps out of a pistol is a reasonable limit on CO2 anyway, as trying to get more will just waste CO2 for any small gains.... The nice thing for you Yanks is that you don't have to go crazy worrying about which side of 500 you are on....

As it is, in Canada and on CO2, and staying within the 500 fps rules, there are lots of choices....

Stock valve and porting (can use light hammer and Disco spring to save a bit of CO2):
.22 cal 12" barrel
.25 cal 24" barrel
Valve extension in 2250 tube:
.25 cal 12" barrel
.30 cal 24" barrel
Bulk fill valve, more volume:
.30 cal 12" barrel
.35 cal 24" barrel

Bob

[sshewins]

Monkey dad, did you mount the b&a .25 barrel in the crosman steel breech? If so, did you have any clearance issues between that 1/2" barrel and the tube?

[Monkeydad1969]

Monkey dad, did you mount the b&a .25 barrel in the crosman steel breech? If so, did you have any clearance issues between that 1/2" barrel and the tube?

No sir, Scott,

I ordered the 35.00 .25 big bore barrel and 46.50 breech with it.  Later on I will get a 9mm barrel for my setup.  The .25 barrel for the Crosman steel breech is 18 7/8" Long barrel  Rifled Muzzle Threads 1' X M12 X 1mm Breech 3 1/4" X .435---the 45.00 one.  Now looking at my Disco breech, w/o the barrel sleeve, I wonder if it will fit the stock breech.











Joe

[rsterne]

12mm LW barrels that are turned down to 7/16" to fit a Disco / 22XX breech will clear the air tube fine without a shim.... Likewise, so will a 1/2" OD barrel, but it JUST touches the tube, not enough to cause a problem, but it does touch.... The .25, .30 and .35 cal barrels that Sean has are all 1/2" OD....

Bob

[Monkeydad1969]

12mm LW barrels that are turned down to 7/16" to fit a Disco / 22XX breech will clear the air tube fine without a shim.... Likewise, so will a 1/2" OD barrel, but it JUST touches the tube, not enough to cause a problem, but it does touch.... The .25, .30 and .35 cal barrels that Sean has are all 1/2" OD....

Bob

Thanks Bob...now to buy a 9mm barrel.   

Will Sean's .35 barrels fit most of the 9mm/.357 pellets from PA?

Joe

[rsterne]

I suggest you think this through before leaping.... While the 9mm barrel CAN be fitted into a Crosman breech and clear the main tube.... that isn't the only problem you face.... Once you turn down the OD to 7/16", the wall thickness remaining is only about 1mm.... since that is supported by the breech it's strong enough to stand 2000 psi, but you MUST use a barrel band to prevent it from getting bent where it exits the breech.... Next, the rear bore of the Crosman breech is only 1/4", and that means the loading tray is wayyyyyyyyy too narrow to accept a 9mm pellet, it will barely work for a .25 cal.... In addition, the bolt is only 1/4" in diameter, so you will need a larger one of those as well.... and a way of sealing it into the barrel at the breech.... The same applies to the .30 cal barrel, you need to open up the bore of the breech at the loading port and make a new bolt.... Can it de done?.... probably.... Easy?.... no, I wouldn't want to try it, because although drilling out the bolt portion is easy, you still have the problem of enlarging the loading tray....

One other additional problem is the diameter of the transfer port.... For a .25 cal you can get away with the 1/4" hole in the breech and use a piece of poly tubing.... If you do that for the .30 or .35 cal, you won't be able to make it breathe properly, so (to let it breathe) you need a 5/16" OD transfer port.... You can drill out the breech for that, and the main tube, and machine a larger OD flat spot on the valve, but when you get to the barrel, how do you seal the transfer port to it?.... On the .35 cal there isn't enough wall thickness left to machine a 5/16" flat without going through to the bore.... On the .30 cal the flat would leave such a thin wall it would likely get damaged during machining or use.... although the .25 cal is fine, I've used a 5/16" OD transfer port on a 7/16" OD in that caliber.... There is barely enough room for a 5/16" OD transfer port flat in the full 1/2" OD barrel in .35 cal.... I use holes up to 7/32" on a 5/16" port, great on a .25 cal, pretty good on a .30 cal, but a bit on the small side on a .35 cal (although good enough for ~120 FPE @ 2000 psi)....

I just don't want you to order a .35 cal barrel expecting it to slide into a Crosman breech in any easy manner.... CAN it be done, yes.... Is it EASY, NO !!!

Properly chambered, you can use Sean's barrel up to my 129 gr. boattail, including any flat based bullet of up to that weight or slightly more.... it has a 26" twist....

Bob

[Monkeydad1969]

Thanks Bob.  I already have the big bore breech from B&A that accepts the 1/2" OD barrels (I didn't make that known in my earlier post, sorry).  It is good up to 9mm so that is why I am looking at the .35 barrel from Sean.  I have read enough of your posts and gained quite a bit from you.  And I always appreciate you giving me your advice.

Thanks for your input,

Joe

[rsterne]

I finally got back to this build today.... Sean Pero shortened and threaded a 2260 tube for me so that I could use two CO2 cartridges or a bulk fill.... I made the piercing cap, and I already had a B&A Bulk Fill adapter kicking around, and there is enough clearance to rotate it under the barrel, so I can use either setup.... Here are the parts....



The valve incorportates a piercing cap as shown earlier in the thread, and the piercing pin in the front is sealed with a 5/32" ID O-ring on it in a recess in the brass plug which is held in by a drilled Crosman 2240 front cap.... The aluminum knob is set-screwed to the piercing pin.... You insert the two cartridges as shown (bottom to bottom) and screw in the plug until it pierces one cartridge, at which time the pressure stops it from rotating.... Then you simply push on the plunger to pierce the other cartridge.... Alternately, you can use the bulk-fill front end and fill from a CO2 tank.... You only get a few more shots with the bulk CO2, but it's a lot cheaper.... There doesn't seem to be any particular difference in performance, but you do get a larger cloud of CO2 blown out the barrel with the bulk fill setup....

After initial testing, I found that the velocity was about 440 fps, with either the 45 gr. JSB pellets or .30 cal roundball (40 gr.).... The roundball was not very consistent in diameter, and the ES was larger, so I decided to refit a stock hammer (instead of the 50% lighter one) to increase the velocity.... I'm using a set Disco spring, running in a stock, fixed 2240 end cap, with a spring guide that brings the length back up to that of a stock spring.... The velocity is now about 487 fps (nearly 24 FPE), and the fastest I saw over several clips was 495, for a good solid 14 shots (2 full clips) on two cartridges.... The increase in power burns up a bit more CO2, but it was worth it to get closer to the <500 fps non-PAL limit.... The velocity peaks at about 60-65*F, and the gun shoots a bit slower when either hotter or colder, so the valve is operating in the balance zone.... This also means that you can fire a whole clip as quickly as you can recock without the velocity dropping.... Here is the completed pistol....



The gun weighs 2 lb. 14 oz. ready to go including two cartridges, a 7-shot magazine, and the red/green multi-reticle holosight.... While doing the Chrony work inside at 20' I had several 7 shot groups that were just one ragged hole.... I love the way it cocks and reloads with the left handed bolt without having to remove my hand from the grip.... This has been a fun project, resulting in a very useful .30 cal CO2 Pistol....

Bob

[Big Bore Bart]

  Correct me if I'm wrong, but as it's marked 2260 on the tube, can you add a stock and take it hunting?

[AmBraCol]

I thought I was following this post, but it dropped off my radar at some point.  Thanks for sharing it with us, I'm going to have to go back through and analyze a few things to get my brain around what all is going on  here.  Other than cool.  Cool is definitely going on.  :-D  You're limited to 500 FPS, we're not.  BUT you can obtain about any parts, pieces, etc you desire while we can't.  Especially barrels are hard to come by.

[rsterne]

BBB, yes with a stock it would be legal for hunting in BC.... As it is, it is legal in Ontario, they can hunt with handguns there, providing they are under 500 fps....

Bob

[rsterne]

The .25 and .30 cal liners I used are available from Mike at TJ's.... Mine are 12.5" long, only because that was half of the 25" rifle barrels we had him make for us....

Bob

[Tommy]

As i am new to airgunning and not that smart , members like Bob are what keeps me here, reading and learning.
Thank you all
Tommy

[AmBraCol]

BBB, yes with a stock it would be legal for hunting in BC.... As it is, it is legal in Ontario, they can hunt with handguns there, providing they are under 500 fps....

Bob

The longer I live the more "impressed" I am with the legal mind.     So they've got restrictions on how a pellet rifle/pistol/gun is set up if it's going to be used for hunting?  Also didn't realize you've got the same variety of legislation depending on location that they have in the US of A.  Sure makes it hard if you're used to one locality and move to another.  What's perfectly OK in one jurisdiction will get you strung up in another. 

Thanks for the insights not only on the inner workings of the air powered projectile launcher but also the intricacies of Canadian law as regards the same.  Who was it that said "The law may confound reason but reason may never confound the law."??

[rsterne]

Hunting regulations (including the no-handguns for hunting in BC) are set by the Provinces (except for Migratory Birds, which is Federal).... The laws governing the guns themselves are Federal (eg. under/over 500 fps.... rifle vs. pistol).... Hunting Licenses are issued by the Provinces, the PAL and R-PAL (Possession and Acquisition Licenses) are Canada.... 

Bob

[Bryan Heimann]

Pretty frikken' smart!  I love your big bore CO2 pistol, especially because it can operate on cartridges at that power level.  Have you ever built a smoothbore version?  And have you experimented with different twist rates and round balls?

[FelixK4]

Wow! rsterne all your projects are really awesome. I was trying to figure out how to get two co2 cartridge in my 22xx like the qb78 and couldn't figure anything out.  I'm not really technical but did you just take the piercing pin valve from an extra 22xx valve and attach it to the air tube cap?