Well, I'll throw this in as related. When I was in high school, a friend of my folks named Don (last name withheld) found out I had built a couple flint rifles, and asked if I could repair his rifle. I said I'd at least take a look to see what was up. What he had was an original half stock rifled caplock. Plain as a yard of pumpwater. Maybe a slight perch belly. Capbox on the side. Maybe 36 cal. No name.
So Don's story was he shot it all the time, often with shot. He was out with a friend shooting/hunting with shot in the barrel, when he said to his friend "Nuts, I can't shoot this. I forgot to patch the shot." To which his friend replied, "What do you mean, you can't shoot it?" Don says "I didn't patch the shot. If you don't patch the shot, you'll blow out the drum." Friend says, "You're crazy. No, it won't." Don says, "Sure it will. Watch." He pulled the trigger and proceeded to blow out the drum.
Well, out of the deal I got to handle an original for a while. I replaced the steel ramrod with a proper wooden one. But I did not try to replace the drum as I didn't feel comfortable with my skills at the time.
The moral of the story is, yes, you can shoot shot from a rifled barrel, but use a patch. Don't know what the pattern would look like. Don't know what would happen with a flinter and unpatched shot. I'll let Larry Pletcher test that one.