SpudFiles

I built this air gun out of steel pipe. The tank is 1 inch steel pipe, the barrel (not shown) is 1/2 inch copper pipe or 1/2" SCH 80 PVC pipe. The ball valve is the pilot, and you fill with the quick disconnect. I also made a brass adapter to use a bike pump instead of an air compressor. Barrels are interchangeable and I have a 1/2 inch PVC plug as a dust cap when no barrel is installed. Barrels are just screwed in hand tight. This air gun is very loud and makes a big bang when it goes off. Ammo is AA batteries and 1/2 inch dowel sections. I also have a custom machined brass projectile. Corks are also a good option, and corks can be supersonic. In the first picture you can see a brass street elbow, it was later replaced with a galvanized one as you can see in the second picture.

I like the ergonomics so you can hold the tank with one hand and use the elbow as a pistol grip and the ball valve handle as a trigger. Did you try out different pilot valves? It seems like you could get away with a smaller valve than a 1/2" ball valve.

Auxiliary, I used the 1/2" ball valve because I had it lying around. I hold the tank with one hand and pull the valve with the other. The elbow does not make a good pistol grip. The top port of the QEV is where you hook up the barrel. At 150 PSI I shot an AA battery through thick plywood using the 1/2" copper barrel.