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 Post subject: Re: Home made air rifle
PostPosted: Thu Jul 28, 2016 8:13 pm 
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Joined: Sun Jan 09, 2011 8:07 am
Posts: 3320
Location: Central West River Nova Scotia
rsterne wrote:
If your valve is 1.5 CI, and you are filling it to 500 psi (34.5 bar), you are using (1.5 x 34.5) = 51.7 CI of air (at 1 bar) per shot.... In most PCPs, that would produce more than 50 FPE of energy, but with your low pressure you are unlikely to get that.... However, I digress....

Your Hatsan AT-44 cylinder starts off with 180 cc (11 CI) of air, but you need to subtract the volume of the regulator.... I'm guessing that is about 1.5" long, which would be 1.3 CI, leaving you 9.7 CI of usable volume.... If you start at 3000 psi, and end at 500, that is 2500 psi usable (172 bar), so you have (9.7 x 172) = 1672 CI of air available.... Divide that by 51.7, and you get 32 shots....

You are getting 571 fps with a 25.4 gr. pellet, which is 18.4 FPE x 32 shots = 589 FPE total energy per fill.... That works out to only (589 / 1672) = 0.35 FPE/CI.... which is about 1/3 the efficiency of a Hatsan AT44.... You can do similar calculations for the other combinations of projectiles and valve volumes....

Doesnt look so good on paper eh Bob. but Im happy with it, since its home made. I guess I won't get rich on it.

If I had only one wish, it would be to be able to "unsay" things.

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