Mike Scott,
Go to 'backyard cannon fun' and look at the firecracker cannon there, read response after response.... 30,000+ views. It was designed by Rays89 and built by us for years. We have sold them all over the world. They are considered by some of the best and brightest on this board to be 'bullet proof'. They are made out of 3/4 stock, FC360. It should be noted that, altho, we are having discussion about a redesign, no specific diameter has been decided on.
Michael