Chamber/Piston to Barrel Ratio for Choking?

[cowscankill]

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.

-cowscankill

[jrrdw]

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: