Thread: Anyone played with 223AI?

Originally Posted by grandpamac

Greetings again,
There is no accurate way of converting CUP to PSI. At higher pressures the PSI figure is higher. At lower pressures the two are about the same and at very low pressures CUP can be higher. Some cartridges like the 7mm SAUM have a max pressure of 65,000 PSI so Greg's figure of the same as a boundary for problems seems a bit low. CUP measures the area under the curve of pressure and not the maximum pressure developed where PSI measures the actual maximum pressure. John did have access to pressure testing equipment but I can't recall what sort.
Regards GPM.

CUP was measuring the deformation on a calibrated copper disk or cylinder after firing, I havnt heard of it showing area under curve before, is there a time component applied to it somehow to get area under curve as they do now with transducers? that would be interesting.
How did you come to 70000 psi from 60000 CUP? the equation I used is supposedly for the higher pressure range and yes there is a margin of error there so its not exact. .
Im running on memory here so I could be wrong about G Duelys numbers but 65000 as a max working load seems about right? That extra 5000psi to get to the 70000psi Mr Barsness is saying hand loaders are running is a substantial increase, and i would be surprised if brass was holding up to that abuse, but again so many variables and so little definitive information. .