Mike is correct. You can draw no conclusions about a shell's chamber pressure from it's ability to cycle a gas autoloader. Gas auto cycling is dictated by pressure-dwell at the gas port.

It is possible to concoct a load that generates high peak chamber pressure, well beyond SAAMI spec, yet fails to cycle the action. Conversely, you can construct very low chamber pressure/high payload shells that will cause a gas auto to overcycle, and batter itself to death.

Sam