Barrel length equals more F.P.S?

[Ducati250Single]

Is there any documentation as to barrel length and velocity? I know for a regular firearm the longer the barrel, (to a certain extent), the more muzzle velocity, which equals more fps. I am wondering if the same is true with airguns. If you had 2 identical airguns, say 2 pistols and one had an 8" barrel and one had a 16" barrel, both pumped the same amount of times, would the loner barreled piston chrony higher? Or would there be no difference, after all a powder explosion is a lot different than just releasing compressed air...or is it? Looking forward to hearing your opinions.

[Ducati250Single]

Had a typo..."would the longer barreled pistol chrony higher"?

[39M]

Is there any documentation as to barrel length and velocity? I know for a regular firearm the longer the barrel, (to a certain extent), the more muzzle velocity, which equals more fps. I am wondering if the same is true with airguns. If you had 2 identical airguns, say 2 pistols and one had an 8" barrel and one had a 16" barrel, both pumped the same amount of times, would the loner barreled piston chrony higher? Or would there be no difference, after all a powder explosion is a lot different than just releasing compressed air...or is it? Looking forward to hearing your opinions.

Probably depends on how powerful the pistol is, what caliber it is, how heavy a pellet is used, and how many times you pump it.

As to the reference of a pb getting more velocity with a longer barrel; that depends on the cartridge. A 22lr pb will attain full velocity at around 12" of barrel length. http://www.ballisticsbytheinch.com/22.html

[mobilehomer]

A pneumatic, pump or pcp, will gain fps with a longer barrel, to a point. A springer is opposite. A shorter barrel, more fps, to a point.

[Ducati250Single]

"Probably depends on how powerful the pistol is, what caliber it is, how heavy a pellet is used, and how many times you pump it."
The scenario was same pistol, same caliber, same pumps.

[45Bravo]

Yes to a point..

Speaking from crosman 22xx experience, given the same gun/pellet combination, just a different barrel
(Crosman 2240 with a 18 inch barrel, and one with an 10 inch barrel) the longer barrel will chrono faster.

But a 24 inch barrel will probably chrono slower as with the factory valve volume a 18-20 inch barrel seems optimum.
.

[39M]

"Probably depends on how powerful the pistol is, what caliber it is, how heavy a pellet is used, and how many times you pump it."
The scenario was same pistol, same caliber, same pumps.

yes, but you didn't give any specifics. With a very heavy pellet you might not see the gains with a longer barrel that you would with a very light pellet. And same is true with 5 pumps vs 15, or if your pistol is only capable of 300 fps.
And larger calibers can often times use shorter barrels since they can make use of the energy more efficiently.

[Ducati250Single]

Thanks mobilehomer, I didn't know about the springer. But on the other hand a springer doesn't compress the air until you pull the trigger. Interesting topic to me.

[Ducati250Single]

Sorry 39M.

[Airgun.Sniper]

 From my understanding it wil increase fps until a certain point


 Cheers

 Jay

[rsterne]

The scenario was same pistol, same caliber, same pumps.

1 pump, the shorter barrel may be faster.... 10 pumps, the longer barrel will be faster.... Somewhere in between (likely 2-3 pumps) they will likely be equal.... As a rough guide, the louder the report, the more benefit from a longer barrel.... because there is still significant air pressure left to further accelerate the pellet....

Bob

[K.O.]

it is all a mix of valve volume, psi, barrel length and projectile weight...  that's a pump and dump

a 1377/1322 has a valve volume of about .1 ci with careful work it can be opend up to about .13 ci  it loses velocity at the lower pumps but draws even at about 7-10 pumps... and past it gains...

with that extra volume a longer barrel helps more...

 a stock 13xx is at about 1000 psi at ten pumps stuff the piston and over pump and you can get about 1500 psi pretty easy...

the more psi the more a longer barrel helps... 

a heavy pellet accelerates slower so if you have enough valve volume/pressure the longer barrel helps push that heavy pellet more...

it is all a balancing act...

http://www.gatewaytoairguns.org/GTA/index.php?topic=71683.0

[BillK]

Yes a longer barrel will shoot faster.  I have only tried longer barrels up to 24" and they shoot faster on the same gun than a shorter barrel.  I have only tried this on Corsman 1377 & 1322 & 2240 & 1740.

[phoebeisis]

K O(asking you because you provided numbers-no reflection on other members)
Quick  questions-on my recent-12-2015 -vintage 1377(fun gun)
1) what is the storage chamber volume-in cubic inches or CC
2) what is the peak pressure it can hold-stock
3) is 1.5cc per pump correct(.1cubic inch)

a .177 barrel-10 inches  I think that is 4cc volume
so 10 pumps= 15 cc and the barrel is 4 cc
Is that about right
10 pumps=15 cc STP- not STP but it will lose some of the extra heat energy as it expands
.177 barrel volume=4 cc

So it has 4x as much volume of STP air  as the 25cm barrel?
Springers have maybe 100cc-my 460 has 115cc- and it has a very high 50-250 ATM peak pressure-

Seems like springers could benefit from more length more than benjamin pump type
But my 460  9 3/4 lbs(scoped) 45" sure as HECK doesn't need more weight or more length
Thanks
Charlie

[K.O.]

1. same as I stated above about .1 ci

2.  Not really sure...   http://www.gatewaytoairguns.org/GTA/index.php?topic=77463.0

3.  stroke is 3.5" and i.d. of pump tube is .62 (iirc)  pi x r²x l   gives pump swept volume...

pump swept volume + valve volume                   gives total volume 

total volume / valve volume                                gives compression ratio

Compression ratio  X  atmospheric pressure          gives  psi  per pump     ( http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html )

 for barrel volume same pie are squared x length...

springers have only one stroke and rely on a very small high pressure pulse...

[phoebeisis]

K O
Thanks
So all that air is stored in just .1 cubic inch-
 that tiny .1 cubic inch valve storage chamber can hold 10 cubic inches of air-100/1 compression
my 460 has just 7 cubic inches 114 cc
so the pumpers could have an advantage-more air to work with
so as you guys say-pumpers should get more advantage from more barrel length
I didn't know that the valve volume was also the "combustion chamber" volume
and it can be boosted by 30%-
my 460 sure as heck is long-and heavy enough-9.5 lbs-10/22 HB scope sling under 8.5 lbs!
Thanks K O- I'm new so taking a while to understand these guns
charlie