If I plug 7mmRM 70 gr H4350 140 gr BT 26" into QL I match my chrono reading 3400fps 75 kpsi.
If I plug the Hodgdon max load [59gr] into QL, I get 45 kpsi 2900 fps [not nearly as good as a 7x57mm Mauser can do with long brass life].
If I look for the SAAMI registered max average pressure for the 7mmRM it is 61,000 psi. Yet the 7mmRM case head is stronger than the 270Win [Mauser type] case head that is registered at 65,000 psi.
If one calculates Von Mises stress for the belted magnum case head for C26000 brass (cartridge brass)Temper - H06 Tensile yield strength - 65,300 psi, one gets the case head plastic deformation threshold at 79,597 psi chamber pressure.
QL thinks it would take 71 gr for the pressure for Von Mises calculated yield, but I am not seeing it in the brass until 72 gr. I measure the threshold of extractor groove growth which is more sensitive and consistent than feeling primer insertion force. 71 gr was calculated. 72 gr was measured. I back off 3% from the more real measured for my 70 gr hunting load for the past few years.
I have a 7mmRM with a Win barrel, one with a Rem barrel, one with a Shilen barrel, one with a Ruger barrel, and one with a Browning barrel.
When I chambered 4 of the 6 barrels, I did not use the 0.220" to 0.227" headspace numbers per SAAMI. I headspace at 0.215", because I have never found a piece of belted magnum brass greater than 0.215" to the end of the belt.
