I am not sure if anyone has mentioned this but I found that PVC end caps sanded down to fit your barrel work very well. They are not very powerful but they get great distance. My 1st combustion cannon had a 1.5" diameter barrel and I sanded down a 1" PVC end cap and got great results.

you could do that, what i meant was that we used raccoon shart for ammo

Wow that is really funny and sick at the same time.

If I were you I would just cut a piece of steel pipe with the same internal diameter as your barrel and melt some lead. I just made one a few hours ago for my first pneumatic cannon. It works great besides the fact that I did not have the right size steel pipe so I had to file it down. That took a l...