Black and Tan (and others), you need to know that the proof pressure hasn't actually changed since the previous proofmark system, when 12 bore guns were marked 850 bars. Those measurements were based on the old lead crusher system. Gunman's figures (950 bar for the 12) doesn't represent a change, but rather a conversion from lead crusher measurement to electronic transducer. If you're familiar with older reloading guides, think lead units of pressure (LUP) vs psi.
One of these days, we're all going to start speaking the same language when it comes to proof and service pressure . . . but I'm not sure I'll live to see it happen!
