Well i am thinking I would like to cut the barrel length of my B22 to the optimum lenght needed. I am wondering who out there has cut the barrel on the B21/B22 and what length worked out best. I assume if a gun like a TX200 can get away with an 8" barrel the B22 can go substantially shorter than the stock lenght, I am thinking of cutting it to 15" from the stock 20". Any tips or experience appreciated!
James, so in your exerience shortening barrels on these was there any advantage at any length? Was this a B21 or B22 you shortened? I would imagine due to the volume of air and the bore size you could cut the .22 verson a little shorter than the .177 before effecting velocity. There must be some formula for stroke length of the compression tube, diameter of the tube and the bore/barrel to figure out at what point downt the barrel the pellet is no longer under infulential pressure. I suppose I could try to calculate it, anyone know what the bore specifics for a b22 are, or this formula?
Good luck, Ed, if you try to tackle it. At least I hope you have...
April 1 2002, 9:32 PM
...better luck than I did.
I worked up a numerical simulation of springer internal ballistics that seemed to look pretty realistic. It predicted that the optimum barrel length for max MV with a 7.9gr pellet (primarily determined by the duration of the piston pressure pulse) for a .177 B18 is 10".
So you can imagine my chagrin when I chopped a B18 to 10" and LOST 40 or 50fps with CPLs over the stock 18" barrel length!
Now the best I can get from my B18 carbine shooting CPLs is 812fps -- 11.6fpe. I, like James with his B22, think I see improved accuracy (maybe due to the shorter lock time), but it did cost about 10% in ME.
Steve, well it looks like you already tried my thoughts out. there must be some portion of the equation that takes into effect the compression of the air and what that does to the volume of the chamber. But who knows, it probably doesnt take much to be off alot, like if you are off on the stroke volume just a bit that would really screw up figuring out barrel length as a little air in the chamber is alot more in barrel length. if this was a .177 gun (B21) i would not worry about 40-60fps, but thats alot out of a B22 velocity. Maybe I oughjt to get used to the length!
It sounds interesting to me cause I have a B22 too. I think there is more to figure in than bore and stroke and how much that displacement will fill the barrel. A big thing would be the microseconds of extreme heat from the air being compressed so high. In another instant the air is cooled back down by the ambiant temperature of steel around it. Any ways air expands when it is heated and that is part of the equation for optimum barrel length. Also I talked to James about his barrel shortening experiments. I may be wrong but I think he was only doing it on .177 B21 rifles, not the B22, I apologise in advance if I am wrong on that. Bottom line is, I want to encourage you to try a barrel chop on a B22. I'd like to know your results. I already put a muzzle brake on my stock barrel so I'm not in a hurry to cut it off...yet.
Well I want to do this but I want to fully investigate it before I make the commitment because the gun really is nice as is, I just think it would be better with a shorter barrel. But I dont want to do it without feeling sure it will be better. Once I get alot of feedback and make a decent decision on length, I will go ahead and post results.
of my B21, it shows the piece of barrel I removed along with the other "Extensive" work I did to "Sporterize" my B21. BOTTOM LINE: Shoots better than before for accuracy, I haven't chrono'd it so can't say if lost speed but it sure doesn't seem like it. Overal length is now 37 1/2" and it weighs in at about 7 1/2 #'s.
see sight below for pics posted back in January:
Modified B-21, by Airheaded.
January 8 2002 at 8:53 AM Eddie (Login Adiberts)
from IP address 220.127.116.11
If you shorten the barrel, you might want to try and
April 2 2002, 7:35 AM
reduce the transfer port diameter a little, I would try about .003 smaller. This will boost the velocity of the air passing through the port, The volume of air reaching the pellet will be reduced, but then the barrel is now shorter, and should not requier as much air volume. Good Luck James P.
This message has been edited by jpsaxnc on Apr 2, 2002 7:52 AM
Interesting logic, James. And quite possibly correct. On the other hand...
April 2 2002, 10:00 AM
...I was guessing that reducing the transfer port area would tend to lengthen the duration of the piston pressure pulse. Which would seem to be the opposite of what's wanted to deliver max energy over the shorter time the pellet will spend in a shorter barrel.
So I wonder if, all other things being equal, a carbine might want a larger transfer port -- not smaller.
Of course, given my record of "success" in predicting springer behavior, anybody might be wise to seek my sage advice -- and then go bet on the OTHER horse!
you can remove the rotary breech to work on it. Being aluminum, you could drill and tap it oversized, then buy some full length set screws and drill them out with various sized ports and screw them into the block, leaving the optimal size in the gun for permanent use. RB
the kind you can get from a hobby supply place, inside the transfer port. Then slowly and carefuly ream it out to the desired size.Or depending on your ability, and resorces, solder, a piece in the port and ream to size. Good Luck James P.
Super glue wouldn't last one shot. The transfer port is one hellacios place to be in a springer. Especially if you have a little too much oil in the gun. You could remove the compression cylinder, remove the breech seal, and braze the transfer port closed with brass. Just don,t fill in the recess for the breech seal. Then redrill the transfer port smaller to the size of choice. Seems like this would smooth out the second recoil, but increase lock time at the same time- not good.
Hi, Jim, I have Made interchangeable transfer ports
April 2 2002, 12:49 PM
for a chiness springer that I have, going smaller did smooth out the recoil, as far as locktime, it was still faster than anything I was doing while holding and shooting the gun, I was also able to increase lock time to a very noticable degree in this gun by skeletinizing and shorting the piston. Still no noticable change in accuracy. James P.
This message has been edited by jpsaxnc on Apr 2, 2002 12:51 PM
or the total weight of the moving mass ...more likely to experience spring bounce... increased pellet sensitivity... increased liklihood of dieseling...and a sharper (faster) recoil which MAY be rougher on scopes. Maybe a couple other things too. Regards, RB
Hi, Russ, Yea lightining the piston in another springer I have
April 3 2002, 9:27 AM
did increase detinnation, I like the idea of Making threaded TP. inserts for the rotory breech, I was thinking of shorting the barrel, 2-3", I'm sure there will be a velocity loss, it will be interesting to see if it can be regained. James P.
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