[gnarcoregrizz]

I made few of these when I was a kid. My pièce de résistance was a 10' 'coaxial piston launcher'. It scared the bejeezus out of most people... I usually shot ice slugs, which would throw a hole in a piece of plywood at 50 psi.

A golf ball with a chipped off shell fits perfectly in a 2" PVC barrel. The problem with chipping off the shell (along with an unrifled barrel) is that it makes it like a knuckleball - you have no idea where it's going to go. They would curve violently in any direction. One of the few times I shot one of these, it curved directly upwards, and I'm guessing landed a half a mile or so away. Hopefully it didn't hit anyone or anything. That was the last time I shot it.