Tuning 25 cal bottle rod with modified valve, advice pls.

[Wasatch]

I've got my bottle rod together and am in the process of tuning it. I modified the valve boring out the cap to 3/8" and replaced the stock valve spring with a conical paintball spring. The spring is softer and longer than stock so i trimmed the valve cap so it is preloaded more than stock. I also opened up the valve port, transfer tube and barrel to 0.157". The hammer spring is a 12.5# unit. The spring preload is set at minimum, hammer stroke is max and the air metering screw is 5.5 turns out. My gun is currently averaging 51 fpe shooting JSB Kings for 24 shots starting from 3200psi. If I filled to 3300 i'd get another 4 shots within 3% completing the upper part of the string.

I'd want to attempt to increase the efficiency more to possibly get 4 full mags within 3% ES, by replacing the conical valve spring with a stiffer unit and opening up the porting further to icemaker tubing ID. Maybe angle the valve port some. Boring out the valve body is more than i think i can do using hand power tools. Maybe add a BHB to stretch out the downward side of the string.

Any advice would be appreciated. Thanks!

[Wasatch]

Searching around lighter valve springs are recommended for power. Is that in conjunction with the stock spring? In my case, with the above string and 12.5lb hammer spring would a heavier valve spring push the curve to a lower starting pressure? I'm curious.

I have a lighter hammer spring, stock I think, that I could use with the 0.17 porting to also decrease the time the valve opens. Or can i open up the porting to much and loose efficiency?

[ksfastman]

What bottle are you using? That gun is awesome looking