RE: smooth bore
I've got a 20 bore fowler I shot ball in as well. I don't use wads for ball, simply a cloth patch. Accuracy is good to 40 yards, loosens at 50, and then gets iffy. Fifty yard groups with my gun will run about 5 to 6 inches, good enough for whitetails or bigger. I've got some paper cartridges made up, haven't had time to test them.