HawaiiPD

The 3120 BAR stamped on your Wm Douglass is the European Controlling agency CIP's minimum proof pressure, which is 30% over the Highest Mean Service Pressure, that is, the actual pressure developed by CIP approved "factory" loads. This is 2400 BAR for 470 NE, but that is a copper crusher measurement.

Bob Forker in "Ammo and Ballistics" gives the Pressure Tansducer equivalent pressure at 2700 BAR which converts to 39,6790.6 psi, slightly higher than A Squares "red Line".The conversion factor you used is for relating "atmospheres" to psi. The correct factor for BARS to psi is 14.50377; similar, but different!

But, I don't know how this relates to SAAMI pressure tranducer figures.