Hoop stress for thin walled cylinders equals pressure times radius over thickness. 20,000 psi is a reasonable working stress level for mild steel (like Greener would have most likely used). For a 12 gauge barrel of 0.730" diameter (0.365" radius) and a internal pressure of 200 psi, we would calculate a thickness of 0.0037". That thickness would fit nicely to the story of Greener cutting it with a pen knife.

Last edited by Rocketman; 12/06/06 08:41 AM.