Someone here posted something to the effect that if a dud round was rotated around and away from the barrel, and THEN fired, it could cause a fatal injury.
I don't think so, and there's no reason to believe that. The bullet would leave the cylinder at greatly reduced velocity because the bullet would be unrestrained before pressures could build up much. I'm guessing less than 400 fps. Might nor even damage the gun if the frame were struck. Shooter might get a few tiny pieces of bullet material stuck in various extremities, but not much else.