Technical question.

[zpaulg]

Hypothetical question.

Suppose I have a 26inch barrel rifle.

I think it's a tad unwieldy.

So I lop off 10 inches and recrown.

Is there a formula to determine the resulting power drop?

Incidentally, that was the technical qiestion bit!

.??

[tinbum]

Or possibly power gain. But in short: Yes. All we need to know is the swept volume, static compression ratio and lost volume.

Edit: oops, I assumed it was a springer.

[hmangphilly]

Hmmmmmmm

if you are cutting and recrowning , it suggests you are cutting at the muzzle end .

so doubt if a formula can calculate the effect of removing your choke if you have one ...certainly would need more info .....

[Loki_79]

Is it a pcp or springer, as the effect will probably be opposite - increase in power for springer (less barrel friction), but possible decrease in power for pcp (depends how long the valve is open, i.e. how much air is released per shot). As mentioned, if removing from the muzzle end, you will have to worry about the effect of the existing choke. If the accuracy is currently good, try to shorten from the breech end.

[max headroom]

There is no power drop. i took my superstar down to 8 inch barrel and put a silencer on. there was no difference in power.
chairgun is your friend.

[Rickenbacker]

I doubt it's a springer with a 26" barrel. The old style '35E barrel was the longest I've seen, at 22".

Some barrel over cylinder PCPs might be that long, but shortening those would usually require a shorter cylinder to match.

Therefore to be considering lobbing 10" off the barrel, it sound more likely to be something like a Rapid.

[bighit]

I know the Crossman rabbit stopper had a 24" barrel as I put one on my xt2250 and the power went UP.

it came with a 14" barrel if I remember right and made upto 8ftlbs if I remember right.

Crossman xt2250 upto 550fps
rabbit stopper upto 600fps according to pellpax.

[zpaulg]

Thanks for the replies guys. Just wondered not actually got a gun I"m planning to chop but I thought such a formula might exist.

[hareng]

In reply to that I took my Goldstar down from 19" to 8 1/2" and lost 105ft/sec.
Same applied to a TX 13 3/4" to 12" not a vast amount of decrease but to 8" again 105ft/sec.

Pneumatic may go up in power if shorten from 26" to 21" at sub 12ft/lb.

Poor way of shortening from the muzzle, most do it because they cant do it right and still charge the proper job.