https://bobp.cip-bobp.org/en/tdcc_public?page=1&cartridge_type_id=7

This is the CIP pressure guides for all CIP proof shotguns now. From it you can see the proof level of 850 and the PT max service level of 740 bars. This is just an updated value in bars, instead of tons per square inch.

Formula: multiply the value in bars by the conversion factor '14.503773800676'.

740 bars is 10,732.79 psi. That is the service pressure often discussed. So if your gun has a service pressure of 10,700psi shooting shells in the 7-8,000 is a very conservative safety decision.