how can one find out what pres a shotgun is proofed to by the marks. in other words what specs do the marks mean. I have a double 12 guage shotgun that has a bp under a crown I found that it is a birmingham english black powder proof but cant find the specs.
Dean

I don't think English BP guns have a pressure proofing. Nitro shotguns will have a specific proof listing. My 1898 12 bore Army Navy is proofed at 3 tonnes. Many others are at 3 1/4 tonnes. Later on, I believe they were listed in BAR terms. It's hard to have a pressure problem with black powder, as you're limited by case capacity. Pressure proofing came with the transition to nitro. Bob

there should be more than just a single BP under crown..

i have my handydandy "the standard directory of proof marks".. right here, and it says a cursive BP under a crown is a preliminary proof mark, and the standard BP under crown is the final BP (proof laws of 1904) is the Final blackpowder proof (30% heavier than expected BP load) of 114.2 grains of "powder" and 726.8gr of shot... if there's nothing else, you would then know it, especialy if it does NOT say "not for ball" that it's made between 1875 and 1887.. if there's more, probably 1888 to 1904.

jeffe