Author Topic: air chamber volume?  (Read 1513 times)

Offline Magnum

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air chamber volume?
« on: September 29, 2009, 02:26:15 PM »
This may be a silly question but here goes. I was thinking of trying a re crowning job on a gamo shadow hoping for better accuracy when as usual I starting questioning my self and  then over analyzing:) I started thinking that if the "compressed chamber air" was equal to the volume of the barrel (meaning that the air pressure behind pellet should be spent, just as pellet leaves the barrel) then that would insure that the pellet was pushed all the way to the muzzle... but if I cut the barrel too short the pellet would leave the barrel before all the air had finished pushing the pellet and therefore I would lose FPS ? on the flip side if barrel is to long then friction would slow pellet down if pressure dropped of to early?
 IT seems to me the spring power is the big factor hear choosing the not too strong , not to weak ...or is it simply big spring big power volume does not matter:)
       Is this a valid thought to consider or just to small to matter? I know the Diana  have different barrel lengths using same power plant not sure if crony would show anything different! Tony.

Offline RedFeather

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Re: air chamber volume?
« Reply #1 on: September 29, 2009, 03:41:09 PM »
Spring power seems to have to be balanced with stroke length/chamber capacity.  Some combinations are going to be inefficient.  Barrel length does affect pellet speed.  Too long or too short are not good.

Offline kiwi

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Re: air chamber volume?
« Reply #2 on: September 29, 2009, 05:14:27 PM »
Hi..the point that the pellets starts to move is the highest
point of PSI...After that the piston has nothing to build pressure against
as the pellet is moveing....
A pellet will reach its max fps in the first 10" of its travel down the barrel
 So chop that bugger at anything over 12" and you may pick up a few fps
as you are reduceing friction....

Pete
Kiwi

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Offline Bhawanna

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RE: air chamber volume?
« Reply #3 on: September 30, 2009, 01:02:18 PM »
timmy is the "chop and crown" chef of rws guns.......bring it to the funshoot in two weeks and timmy can chop and crown it for you.  ps....get him to do it before he gets into the nattys!!!!...ha!
The hardest part of getting old is trying to look good naked!