Gauntlet 22 carbine - need some help about barrel length

[shorty]

I am planning on turning my gauntlet into a carbine. First thing for me is shortening the barrel. The problem is, I have no idea how short I can go without sacrificing the power.

I would typically just go and cut it down to 16" and see what happens and deal with it. But, something odd happen yesterday and it's not the only time I heard off this happening and it happen here just recently with MJP ( I think). So I would like to get some kind of understanding before I go and cut.

So,
I have a "just over" 27 fpe tune using 14.3's and I wanted to make sure "without making a changes" threw in a mag of 21.14's. The power went to at and just below 27 FPE. I was expecting an increase in FPE at the same settings but there was actually slightly less power. Yes I can bump the hammer spring in a little and push it over 30FPE but this is the first time that I never had an increase in power using a heavier pellet at the same settings.

Somebody please tell me what's going on and if all possible, what can I expect by shortening that long as$ barrel ?

[oldpro]

 Kind of a hard question to answer but heres my take based solely on experience. A well tuned air rifle will loose 5-10 fps with every inch cut off it, a typical gun will see 10-20 fps drop with every inch THOUGH once you get below 15 inches the FPS drop is more apparent in both a well tuned gun and a typical gun. Hope that helps. So basically the more you cut it down the more it effects the power and efficiency. Ive had guns that had no change in fps or efficiency with 3 inches whacked off the end.

[oldpro]

 My advise is if your going to cut off the choked end do it in steps if your going to cut off the breech end I wouldnt cut off more than 6 inches.

[shorty]

Thanks for the info Travis. If the barrel is really 28" long, I would be pulling off over 10". I can re-choke but I think a target crown without a choke should suffice (I think).

Here's the stock I am looking at:
https://www.pyramydair.com/product/ics-special-weapons-sw5-series-tactical-side-folding-stock-black?a=7973

[oldpro]

Thanks for the info Travis. If the barrel is really 28" long, I would be pulling off over 10". I can re-choke but I think a target crown without a choke should suffice (I think).

Here's the stock I am looking at:
https://www.pyramydair.com/product/ics-special-weapons-sw5-series-tactical-side-folding-stock-black?a=7973

COOL! Cant wait to see how it goes but before you cut off 10 inches I would start at half that and work your way up. No going back after you cut it and no replacement barrels from Umarex.

[shorty]

I was wrong with the porting on the gun. I never checked (verified) the barrel port. I verified it at .14" and then opened it to .166". Should have known better before posting to check this. Valve was .187 exit,TP .166" and barrel port now .166"

I also pulled off 5 inches off from the TRUE 24" barrel down to 19" and put a target crown on it. It is a 24" barrel..... Not 28" barrel.

Fired one shot using the 14.3's at 890 FPS with absolutely no changes from the full length barrel that was doing 920 FPS.

All and all, still not that bad at 25 FPE which is only 2 fpe less.

Boy I tell you, 5" is alot and can't wait to shroud it properly because it was super loud just firing it without a barrel shroud.

[fgwhite]

so when you took shroude from barrle you had 24 left i did mine one time i could swore it was 22 inchs from crown to breach did you check and see if barrle was choked how did it affect accury i wounted to cut mine down to 16 inchs barrle then shroude it to match bacily cuting over all length down buy 6 inchs

[shorty]

With the barrel out of the gun and tip to tip was 24". Never check for a choke as I can re-choke the barrel using the wedding band method that I used on my 22 marauder barrel if it needs it. Worked perfect.

Just have to figure out the shroud threads before cutting that down and make a 3d printed ported barrel cap because it was indeed split down the middle.

It really looks alot shorter now as the barrel only extends about 2" from the bottle. Should swing perfectly with a shroud and 3 baffles.

[fgwhite]

how much did you cut off barrle rocker 1 has new tubes he can make them to fit your gun my idea was cut barrle down to about 16 then have a thread on adapter made that went to 1/2 20 and screw on a nice big ldc still useing the factory shroude to go from adapter back to action block and drill a hole in bottom of it seen one guy cut shroude then he glued a end cap on and then used the factroy baffles or he printed new ones i was going to do away with the factory baffles all together i talked to haja he told me the barrle had a choke i even thought about haveing some one machine the breach end down cut 6 to 8 off the back of barrle then machine o rings and breah and port back in barrle the gun is way to long 

[shorty]

Don't know what to say Fred. I am wing-in it with all the tools I have available.

[fgwhite]

seen this gun and loved it if barrle was a foot shorter well maby not a foot but 8 inchs at least

[mackeral5]

I was wrong with the porting on the gun. I never checked (verified) the barrel port. I verified it at .14" and then opened it to .166". Should have known better before posting to check this. Valve was .187 exit,TP .166" and barrel port now .166"

I also pulled off 5 inches off from the TRUE 24" barrel down to 19" and put a target crown on it. It is a 24" barrel..... Not 28" barrel.

Fired one shot using the 14.3's at 890 FPS with absolutely no changes from the full length barrel that was doing 920 FPS.

All and all, still not that bad at 25 FPE which is only 2 fpe less.

Boy I tell you, 5" is alot and can't wait to shroud it properly because it was super loud just firing it without a barrel shroud.

Sounds great, I bet it looks a lot better.  I'll be anxious to see pics once you get the shroud finished. 

Your results are very much inline with my experience with my QB's when testing with different barrel lengths.  I have a few that I switch between from time to time-  stock QB is 21.5" from barrel port to muzzle.  I have a barrel cut down to 17" as well as a 14".  The 14 is fully shrouded and very, very quiet when on a gun tuned for 20-25fpe.

[shorty]

Thanks alot Fred. I really wanted to go to bed early tonight.

Just for poops and giggles, I made this 2 baffle clear schedule 40 LDC for my marauders ( slip on over shroud ). I used it once or twice but really could not tell a difference since the guns were so quite already and sat it to the side.

Tonight,
I made an adapter for it so it can slip on and be retained by two 8/32's to the barrel. Fired one shot ( everyone is sleeping ) and it is just as quite as if the full shroud was on and had the long barrel.

Can't wait to find out what the tap size is to finish the shroud. It should be so much better.

Here are the pics

[fgwhite]

i like the look of the rifle with the cut down barrle when the qb barrles were cut do you id they was choked any at all i think a short barrle guanlet with a big fat ldc looks great

[Ribbonstone]

Don't have a Gauntlet, but have cut the barrels on some HPA QB's (which is the closest to the Gauntlet). 

How much speed/energy you lose is more related to how it's tuned than any set amount per inch.  Lost the most with "air hogs", the least with reasonably efficienty rifles.

Most gauntlets aren't real efficienty, which would make me guess a higher rate of energy loss.  Likely won't be too much (lets see...if you go from 24 to 16", that's  about a 33% reduction...so I'd expect soemthing between 12% (gas hog numbers) and 6% ("ok" efficency)reduction in velocity.....which might work out to a  21gr. pellet at 760fps/27 foot pounds to something like 670 to 715fps...or about 21 foot pounds to  23.8 foot pounds.

But...if you NEED short, then the drop in energy is the lesser concern (if you NEED the energy, then shortness is the lesser concern).

[shorty]

Ribbonstone,
I always love (and respect) your post with the low cost-low air pressure airguns. I am getting there slowly but I am definitely into this. gun is finally tuned to 20fpe and I am doing the shroud now.

What the heck did umarex put in the stock to make it weigh so heavy on the back end...?

Boy,
If I knew the QB platform was this fun and cheap, I may have started with this instead of the marauders.

[shorty]

3D printed a bunch a parts, shroud cap and barrel cap along with parting off alot of the shroud. I dont's have the thread size for the shroud so decided to just make a cap and super glue it in place (muzzle end).

Plopped in 4 K baffles along with the spring and bingo.

Running just over 20 fpe with 14.3's and she is a quite as a mouse. More quite than the LDC and the LDC just hit the trash can.

Accuracy,
All I can say is thank you Rocker 1 for the tip you gave me at-least a year ago for doing crowns. Works like a charm every time.

While parts were printing out I cleaned up the 5" of barrel I cut off. Guess what? NO CHOKE.

This is my shortest gun so far. To the right is a FDPCP,then the marauders, then the gauntlet.

Gun feels 100 times better with the throw around, cocking (super light spring), efficiency, power level (Ok) and accuracy. Still going forward with the even shorter lighter stock but this things feels real good right about now for a dirt cheap regulated gun.

25 yards covers a nickle with 4 Ice-house (tall boy) beers. Yea I know, quit drinking you fool.

[Ribbonstone]

Thank you...but not likely to find out...not really in the market for a Gauntlet. Not that they are "bad", just that I got started with HPA QB's before there was a Gauntlet and really am not that in love with repeaters to junk what I got and start over (but if I were starting over, would likely start with the Gauntlet.)

So not sure about the stock weight...could be it's a solid-butt...could be a weight hidden under the butt-pad.

[rsterne]

This is a case of when calculations will probably give you the wrong answer.... *LOL*…. If the gun was tuned so that the valve was open until the pellet left the muzzle, then in theory the FPE would be proportional to the barrel length.... If you are at 20 FPE with a 24" barrel and you cut off 10", that should drop to (14 / 24) x 20 = 11.7 FPE.... However, if the valve is closing a long ways before the pellet is halfway down the barrel.... that means that will still be closing long before it reaches the muzzle, so what you are left with is the air released by the valve has less distance to expand with the shorter barrel.... There are three guarantees.... the report will be louder because the residual muzzle pressure (after the air expands) will be higher.... and the velocity and FPE will be lower.... How much less depends on how the gun is tuned now.... The lower FPE from the same amount of air means the efficiency will drop too....

Bob

[darkcharisma]

Shorty, that looks really good man. the stock weighted closer to 3 poundslast time i checked. i wanted to throw it away. what did you do exactly for the crowning of the barrel? no choke right? my gauntlet is sitting at 40fpe with the stock barrel. all secrets are in the valve work. i also replaced the tube with  a 2000psi discovery tube. if you need to crank for more power. thats one good way to do it. i am running 1400psi with a 23ci bottle and top out at 80 regulated shots at 30fpe. you might wanna give it a try if your hungry for power.