Thanks to both 2-P and Mr. A for the formuale. I'm trying to determine if these formulae will show whether a small bore (say a 20 ga.) will or will not withstand more pressure than a larger bore (say 12 ga.) WITH THE SAME WALL THICKNESS. I'm at work right now, so I'll have to plug-in later. Thanks again.

Mr. A - USNA = U. S. Naval Academy?