Mark- which is why we all use cloth patched round balls in our smoothbores.
I strongly admit that I need to do more, probably a lot more experimentation with my choked 20 bore as it's accuracy down range with round balls is pitiful. At 25 yards, from a rest, I can make a lovely 1" 5 shot group, quite easily & virtually every time.
At 50 yards, the groups are horrible - well over 5" for most of them, with fliers outboard of that and out of 10 consecutive shots, perhaps not more than 6 or 7 on a standard 11"X8" page target. It's horrible. This innacuracy might be due merely to the choke, I don't know. It's only saving grace, is the virtually Modified patterns with shot - lovely.
Some time ago, a couple summers past, at least, I sat at a bench and made a nice 3" group with a friend's 20 bore smoothie, single front sight, no rear sight and what I'd call normal loading, that being a .600" ball and a .020" patch along with 82gr. 2F powder. In that group, 3 of the 5 were cutting, so it was an honest 3" group, on centres.
So - I know a smoothbore, if properly loaded, can shoot into 3" at 50yards for 5 consecutive shots - all I have to do is to discover what the load has to be, to do that with mine.