Thread: Anyone played with 223AI?

Originally Posted by sneeze

Its an interesting topic. The calculation to convert cup to psi I was using is (cup x 1.516)-17902 which for 60000 cup gives 73000psi. Is there more accurate equation?
I have no idea what method Mr Barsness used to get to the 70000 psi for some handloaders but I have seen many discussions regarding the measurement of chamber pressures and many disagreements, even with modern pressure trace equipment. Greg Duely had an article on this some time ago and if I remember correctly he came up with a max of 65000 psi before case head expansion and function became a problem . Some one may have that article and could chime in? That would suggest even at 70000 psi you would be seeing issues. With some exceptions I will disagree with your claim that most gains could be made with the parent case , I think @zimmer has already pointed this out
The safety margin is another subjective topic and yes we will find our own comfort zone. From my perspective we know the weak link in the process is the brass case. If the case is getting over stressed then we will see case head expansion, loose primer pockets, extraction can become sticky. If none of these symptoms are present over time then I will be happy. Keeping in mind the safety margin for modern actions is substantial. I have a broacher here for the BSA majestic from the early 60s were they are testing the bolt lugs to 11 imp ton with out fail.
I also dont chase the last possible fps but I do like to realize most of the potential of a cartridge.

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.