Thread: .223 77 grain TMK

Originally Posted by John P

Interesting….. I wonder what their reasoning is for doing that?

I think the basic reason is the need for the data to work in semi auto rifles where port pressure is more important than max pressure. Second the PSI system gives a more accurate reading of max pressure than the old CUP system that reads pressure over time from the compression of a copper cylinder. I will look for that podcast @Dicko.
GPM.