[Clark]

I think that actual pressure is a red herring, unless one is selling ammo or writing load manuals.

I work up in my strong rifles until the primer pocket gets loose, and then back off a safety margin.
The hardest thing for me is calculating the magnitude of the safety margin. Vernon Speer wrote 6% for making manuals in 1956. Along with the other variables to consider, I have to include the temperature effects on the powder and the range of temperatures my chamber might be.
So I was grateful when Hodgdon came out with the extreme powder series.
Kombayotch replicated the temperature coefficients.
Then Aliant came out with AR Comp.
Kombayotch replicated that AR Comp is even flatter.

Last year I drove 900 miles to load, target practice, and shoot deer. I had built a wildcat rifle, a 257 Roberts Ackley Improved Rimmed. I had necked down and turned the necks on Norma 7x57mm Rimmed brass. If normal brass should go to 67kpsi in Quickload, then the rimmed should go to 80kpsi. Wrong. The brass was soft and giving up the primer pocket at 62 kpsi in Quickload. I had to switch from H4895 to H4350 and back off from 62kpsi. It did not matter what the numerical value of pressure actually was, what mattered was the effects of pressure. I had to back off from the loose primer pocket effect.