Keep your hand away from the cylinder
Xavier has written about a guy to got his thumb blown off by a .460 revolver.
It is important, when firing a revolver, to keep all parts of your hand(s) away from the front of the cylinder. Explosive ignition gases exit the cylinder gap as well as the muzzle of the firearm when the cartridge is fired. This safety issue is sometimes illustrated by instructors who place a revolver inside a paper bag with the muzzle sticking out a hole in the bottom.
Xavier has also posted the photo of the thumb itself. It is not pretty.
More here.
omfg you gotta be kidding I did that once but around cylinder of a ruger sp101.
got a powder burn thats it about the same as you get from a spitter.
I hope that heals up man that suck so bad.
Hell of a way to make a point about proper grip with a revolver.