Dave, that is GREAT research. I looked in our libraries, and did a google search, got nothing. And here you have the guy's address - maybe I should mail him a letter and see just when he made this beautiful 15-bore. Not too many of them running about, but Track does have the different wads needed in the correct size. Bores are at 0,685".
With those pretty, twisted damascus steel barrels, i am not even going to try shooting balls. I'll stick to birdshot. I have a 10-, 12-, 16, and 20-bore shotguns, one of those will handle a ball.
Of course, with the demise of Goex powder mill, I think we are all going to be hurting for black powder. Got a few pounds of the Goex, and a few of Olde Eynsford, in both FFg and FFFg. After that, it's going to be a slingshot - have one of those also, with a red laser on it even.
Again, Dave - thank you so much for the research.