just use a small barrel, not any larger then the porting.
Or build a larger valve with a larger porting to fire a large barrel at full power.
Yep, that would work.
Thanks Brian, I wasn't aware of an actual working cannon using this valve layout, I have seen concepts though and even came up with one a while back.
There seems to be something wrong with pressurization of the cannon right now, I think something might have become lodged in the equalization hole, it was only 1mm in diameter so that would definitely be a possibility. I don't really want to take it apart now, I am concentrating my efforts on a new version. The problem that has appeared is causing the cannon to fire at a low velocity (apparently, I have not tested it for myself yet).
I must say I am a little disappointed from the feed back of my team but I must take in consideration outside factors. I definitely know what must be done on the second prototype. At least it worked.