I've done round ball in 30-30 rifle. It's a hoot!
.311 cast ball, 45-45-10 lube, seated flush with the neck. 2.2g Clays, 868fps. I keep meaning to try a bit faster, haven't gotten around to it yet.
Accurate enough at 25 yds for squirrel smacking. Pull the trigger, it goes Pfft. Lots o' laughs.