Ok so im home now. The barrel is 2” and the chamber is 3”. The piston was just a mason jar filled with a 3” washer glued to it. My cousin helped me earlier. So when I had the piston in and he pumped aire into the cannon, the projectile we had used moved along the barrel which leads me to think its s...

So I’ve wanted to get into building spud guns in the past and since I just got my first job I figured why not try and build one. Its one of those coaxial (?) ones with a piston in the back. Sadly its not really working. I dont think the chamber or barrel are the problem. And the valve in the back se...