Pressure Limitations in Guns, Cont.

The weakness in the cartridge system is twofold. The extractor undercut above the cartridge rim is unsupported in gun chambers, allowing pressure within the primer pocket which exceeds cartridge brass' elastic limit to expand the case in that area. In the '80s I measured that occuring above 65,800psi cup in the .223 case during tests up to 77,700psi cup.
The other pressure limiting factor is primer blowout (pierced primers) under heavy loads. If the firing pin or striker were locked in place at the time of firing, there would be nowhere for the primer brass to go. As it is, the lighter the striker, the lower the pressure needed to blow out a primer.
It was noted by Hatcher that reducing the Springfield striker weight by cutting off the manual cocking knob, risked primer blowout.