Hoot,
I went back to your earlier post and saw that I had already addressed the groove diameter and noted that the nominal cartridge was clearly shown on the barrel. The gauge marking on the barrel is one that usually goes with a groove diameter of .362-.364".From the barrel marking, it is pretty clear that you can forget about my idea that it could be chambered for 9x58 1/2R S&S. If someone beat me about the head and shoulders enough to make me load black powder cartridges, I would follow Sharps 4590's advice to a "T".I wouldn't ignore "nitro for black" loads, however.It is still a good idea to slug the barrel, to be sure.
Mike
