This is incredibly detailed. And I like the general idea but may I suggest a simpler way? With the right mechanism you don't need shells. Find a way to fill the bolt with gas when you pull it rearward. Then move the bolt forward, as the bolt closes the shell into the chamber, the front of the bolt o...

Best of Luck to you Jamie. We have some experts here on such cannons. I have heard of atleast one gas-operated concept reguarding a combustion tennis ball launches but it is also incredibly dangerous unfortunately, due to the nature of the mechanism.

Again good luck!

Hi Welcome!

Most of the people here have a decent idea about what they like to build and their own areas of specialty. Most of us are amateur and intermediate with a few harbouring advanced knowledge, so there's a bit of everything. Work out what you want from air guns or spud cannons and ask away.

PVC is generally okay for very brief explosions. Anecdotal evidince suggests that you should be safe. But again it comes down to how much propellant and the level of sturdiness. Good luck and be careful. Make sure you use pressure-rated white PVC and wrap the areas of stress in non-stretch tape.