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Chamber/Piston to Barrel Ratio for Choking?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Chamber/Piston to Barrel Ratio for Choking?

Unread postAuthor: cowscankill » Wed Nov 09, 2016 1:40 am

Hello hello again, winter is approaching which means it'll be time again for my yearly pneumatic build. This year it's either going to be a big hefty boomer at lower PSI (aka 100) or a compact HPA metal rifle (similar to Jorge's current Youtube build).

But while considering designs for the large PVC piston cannon, I realized I have no clue what barrel to valve diameter is too extreme. For example, the design I am considering is a 2" Tee Piston connected to a 1" barrel. Is this too big of a difference and will it cause performance problems? Also, would it be better to design the 2" Tee Piston with say a 1.5" outlet that reduces down to the 1" barrel?

My goal as always is to do something even better than my last build, which for me was a bipod mounted multishot .50 cal pneumatic that was surprisingly weak. I haven't done an efficiency/power build in a while so regardless of the design I pick, this year will be focused on muzzle energy/velocity and hopefully noise. I'm personally leaning away from the compact because I miss the sound of those large caliber booms, but all of my friends think I should do the HPA one with a really fancy stock and what not since they're all into sleeker design. I'd have to buy a pump especially for this that would set me back $130 USD (for max psi of 4500) but I'd have it for doing all kinds of compact HPA projects in the future.

Opinions on anything I've posted would be great.

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Re: Chamber/Piston to Barrel Ratio for Choking?

Unread postAuthor: jrrdw » Thu Nov 10, 2016 8:13 am

The Basterd was a 2" piston valve with a 1" bore X 8', duel chamber (3" X 5') built in a cross and had no problems dumping both chambers at 100psi. :bigsmurf:
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