piston cannon question

[zeigs spud]

when i make my piston cannon how do i get my barrel strait and keep it strait in the cannon? Do i need supors in the cannon its self? Also, eventualy with the piston pushing against the barrel soo much wouldn't it eventualy knock it out of place or forward and break the seal around the barrel?

plz help?

[SpudStuff]

Yse a modified bushing or reducer. You can cut off the outter ring so air can flow past.

[Atlantis]

If you can manage it, just put a long bolt through the barrel near the breech end, and either let it rest on the chamber wall or screw it through the wall, 2nd option would need that sealing tape though.