I know it's going to be a little bit tricky to program this in, but it would be a great addition to the roleplay / torture / interrogation aspect of the game.
Revolvers could have a "spin drum" function where a random number generator determines whether there is a round in the chamber or not.
Depending whether you have zero or 6 rounds in the revolver, you'd have a 0% - 100% chance of the first LMB click causing a shot to go off.
Of course, every next shot would have a similar RNG check with a lower chance, until you reach 100% (example three rounds in barrel, first chance = 3/6, second chance = 3/5, third chance = 3/4, fourth chance = 3/3 = 100%). After the first shot, all ensuing shots could be live rounds (rounds not distributed evenly).
To get the initial chance ratio, you'd have to spin the drum again.