Saw a guy do something similar with a .454 because he wrapped his hand up around the cyclinder. Somebody at the range later figured out that the equivilant in pressure and temp out of that 80/1000's of an inch gap was the equivilant of a focused blow torch.
What was funny was to be standing up stairs, hear a loud *Bang* followed closely by a scream, and then see some guy come flying up the stairs and out the door with his hand firmly clutched in his arm pit yelling the whole way. Range master even hollered out, "Hey you left your gun, can I have it?"