The cannon has a simple cylindrical bore. It is in the style of a Parrott gun with a thick breech. Kept the cannons from blowing up. Think the civil war Parrotts were rifled cannons.
I remember proof charging it, but that was 3 decades ago. Gee, can you get the fuse stuff any more? I'd only shoot it with a very light wad these days, a 50 cal round ball would have a pretty long range, and probably a whole lot of recoil. With effectively no sights, it would be hard to predict where it would go.
I don't even have any black powder these days, can you use pyrodex interchangeably?