A few comments on the last couple pages:
1. If you have a British double proofed under the old "tons" system, that figure (which you cannot convert to psi via multiplication x 2,000, nor even 2,200 for a Brit "long ton") is SERVICE pressure, not proof pressure. It wasn't until they changed to the "bars" proofmarks that you got a representation of proof pressure.
2. If you're reloading, you want to focus on SERVICE pressure, which is significantly lower than proof pressure. The reason we have proof is to test guns at much higher pressures than they'll be subjected to via hundreds or thousands of rounds. You can look at the difference between proof and service pressure as a safety cushion. But the best idea is to stay under the SERVICE pressure for the gun in question. If you're feeling gutsy and think it's OK to flirt with PROOF pressure in your reloads, it's good to remember that Winchester did exactly that, with all the American doubles of the period, after their Model 21 came out. And while all the American doubles did survive at least several dozen proof rounds, they all eventually failed--which is no big surprise, because those loads aren't meant for repeated use. They'd kick the snot out of you, and very likely crack the stock before they did anything to the barrels. The Model 21 was the sole survivor of that torture test, after something like 2,000 proof loads.
3. Depending on the gun for which you're reloading, going up to 10,000 psi in the 12ga can be unwise, IMO. The current CIP service pressure for "standard proof" 12's (those marked 850 bars) is 10,730 psi. If you're doing what many of us do, and reloading 2 3/4" hulls and shooting them in guns with 2 1/2" chambers, a 10,000 psi reload per the published recipe can easily exceed 11,000 psi because of the extra hull length. It's safe enough to reload 2 3/4" hulls for 2 1/2" guns, but in that case you need to build in an extra safety cushion if you want to make sure you stay below the established service pressure for the gun in question.
Like Mike Campbell, I've always been either Larry Brown or L. Brown. I post more after the basketball season is over, when I'm not busy coaching.
I have no experience in machining, nor chemistry, nor anything of that nature. I do have a fair amount of experience with vintage guns, both American and foreign. I've written a bunch of articles about them, and I've worked for some pretty sharp editors who've saved me from a few mistakes. When I write about subjects such as proof, I try to be very thorough in my research. I don't rely just on my own experience, which also includes tens of thousands of rounds (mostly reloads) through vintage doubles. All of that is still anecdotal. I try to go to reliable published sources (like the Birmingham Proofhouse, in the case of British guns) as well as information dating from the time when our vintage American doubles were still being produced. Because I do write for publication as well as on various BB's, I always try to give advice that will keep readers on the safe side. If others want to experiment with loads that exceed the service pressure for a particular gun, that's up to them. But I won't recommend it.
Last edited by L. Brown; 04/11/15 06:13 PM.
