OK.
I have a gun that I think has a proof pressure of 8938 psi. In that case, I obviously don't want to shoot 9,000 psi shells in it.
But maybe 8938 psi is the service pressure, meaning the gun was deemed to safe to shoot 8,000+ psi loads day in and day out, for tens of thousands of rounds, for years and years without incurring anything more than normal wear. Hmmmm, should I hang my hat on a number like 8938 when actual pressure testing probably can't distinguish 8900 form 9300 with any scientific certainty? Proof pressure or service pressure, does it really matter? What matters is that 7,000 psi is better than 9,000 psi, right?
It also has 2.5" chambers. Maybe I should buy or reload 2.5" shells with recipes suggested at 7,000 psi?
All I need is some published data, a razor blade and a couple of washers and I can be shooting 7,000 psi, 2.5" shells in my frail old Brit gun. Nah, I have a better idea.
I'll just listen to people who "understand vintage guns." I'll load some 2.75 " shells (with some crappy metering powder and a substitute primer) and shoot them in my 2.5" chambered gun where I imagine my pressure will be around 7000 psi.
(I'll have) "peace of mind and I know I won't go above the published pressure."
Now I understand.
