Donkeys years ago I shot a fox on the run with an un patched ball at 80 odd yards, missed the first shot so dumped in some powder spat a ball down the muzzle, rammed it then killed the fox with a ball through his chest whilst he was quartering away from me. As a one off I reckon you can get away with it in an emergency. I then patched a ball which loaded fine. It was a .490 ball. I think repeated shots would just badly foul your barrel, but not permanently damage it.