My cannon uses a breech loading mechanism adapted from one developed by someone on spudtech a while back. I don't remember who, so please post and give appropriate credit if you do remember. It is a ball valve with a hole drilled in the side while the valve is in the closed position. I load the ammo (.5" steel ball bearing) from the side of the ball valve and then turn the valve into the open position to make ready for firing.
The barrel is a 36" long brass hobby tube with an OD that fits nicely into .5" PVC and an ID that fits the ball bearings perfectly. I also have a small piece of this same type of tube inside the ball valve. I was going to use magnets to hold the ammo in place, but luckily I got a bit of dried glue in the tube while gluing the tube into the ball valve. This makes the fit tight enough to hold the ball bearings in place until pushed.
My chamber is pretty self explanitory, and my chamber:barrel ratio is 3:1. I've only fired it at 15 PSI due to a lack of space (I live in the suburbs), and it put a 1/3" hole into an old door. The QEV is rated to 125 PSI, and my gauge goes up to 100 PSI. I would have made the whole thing metal and bought a higher gauge, but due to the pressure limit on the QEV it's not worth making the cannon heavier. I can't wait to fire it at 100 PSI though!
I think I got the pics up right, but if not, I'll keep trying. I'm new to this, so any comments/suggestions/criticisms are welcome. Hope you like!
-goose_man
