Perfect! Thank you guys. This seems to be an awesome community so far. I'll build a coaxial piston valve and stick it in the upper curve of my air tank. I probably should have planned more before I purchased my fittings but I think I can still make it work. Found a nice animation so it shouldn't be ...

Ah yes, I know that burst disk valve are the best... I just don't want to have to replace the disk for every shot- even if it is inexpensive. Is there anyway I could make a piston valve with the input and the output aligned with each other? like this: --->valve---> not a 90 like: ............. ^ ......

I am building my first pneumatic air cannon. I have a 4ft long, 4 inch, 40 gauge pvc pipe capped at one end and connected to a 4"x3" reducing 90 fitting. It loops with another 90 into a U shape ending at 3". I figured I would add a sprinkler valve next but unfortunately, the largest size I could fin...