To get back on topic... not that cars aren't cool...
I'm not at all sure that commercial loaders load to the higher end of the pressure range to 'function automatics'.
The point of the gas tap is similar between makes, and according to Butler is in the area of 1500-2000 psi give or take.
Chamber pressures can vary from 7,000 psi or so, up to SAAMI max and still function automatics.
It appears to be the volume of gas that counts, which would be related more to total impulse of the shell than chamber pressure.
This 'book' load for a Remington hull with 1 1/8 oz of shot:
Winchester
WAALite
Ched. 209
WAA12
14.7
11,500 PSI
1,090
would at first glance seem to be a real 'hot' load but of course it isn't. I'd be amazed if it worked a stock 1100.
Recoil autos are the same story. They need a certain total impulse to function, and total impulse isn't directly related to chamber pressure.
It's that old 'area under the curve' thing again.
