Jon;
I am going to have to do a bit of digging but I am quite certain I have a proof chart but don't recall which date, that gives the actual Black Powder charge used for the various gauges & lengths of shells. In the muzzleloaders as well as early breechloaders sans choke the proof was done using a close fitting round ball rather than a shot load. The BP charges were extremely heavy though. I do have an I Hollis 12ga MLer which bears the combination mark that both provisional & final proof were conducted as one. The heavier provisional charge was used at final proof. Best as I have been able to determine this mark was not used prior to I believe it was 1887. This gun was thus obsolete when it was built.
