Not too correct Larry but as further reinforcement - SAAMI standards are Max Average pressure in a lot of ammo should be 11,500psi. However, there are two additional pressure limits the gun must be prepared to withstand. The Max Probable Lot Mean would be 12,100psi and the Max probable Sample Mean is 13,000psi. This tells me my 12ga firing factory ammo could very well be subjected to 13,000psi periodically. Whereas 12ga damascus barrel was originally built around an 8000psi load or less. The British reproof pressures are actually very similar to SAAMI but because they are measured with slightly different placement of the transducers appear different.
Actually, unless things have changed recently, those pressures are not measured with transducers at all. They're still using the lead crusher system. Or so the Birmingham Proof House said back in 2001. They gave standard CIP proof and service pressures, converted to transducer psi, as 13,920 and 10,730.
