I'm going off of dimly remembered reference material - not the most reliable of sources, true, but I'm pretty sure I've heard it referred to a couple times.

It's possible in such a situation that the gun would be loaded at minimal charge - after all, why waste the shot? Alternately, if it WAS a case of a fully loaded gun, I'd imagine it would involve being tied down. But I'd lean towards a minimal shot. Still enough to sear anything touching the barrel, but not enough to kill anyone in the vicinity.

Who knows? I stand ready to be wrong. Given some of the punishments I KNOW are correct though, it's not out of character beyond the waste of powder in pursuit of merely punishing someone. But then again, not all the punishments were meant to be survived...

M