All of us, went to a few good classes while in the service.My main concern about a spud gun is keeping the projectile lit.
And my only shot using mapp gas scared the crap out of me. Took the bark off a tree at 30 yards. That tater was MOVING.
The last Potato we played with we used a 3" piece of seamless pressure pipe and oxygen mapp mix as a propellant. And a pezzo to lite it off.