Without wads, it's not going to make the same sharp crack as a ball loaded revovler makes...but the wads by themselves are dangerous for a good distance...could seriously hurt asomeone in side of 15 feet by just a wad.
Proably the best way if you are not pointing the gun at people or things you'd not like to destroy is a good compressed layer of corn meal.
Now I have to warn you...once the blank powder starts toburn, if the muzzle is pressed up against something, the gas has two choices:
1. blow the revolver to shrapnel
or
2. Blow a hole big enough to let the gas escape in whatever substance the barrel is pressed up against.
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DO NOT USE PYRODEX PELLETS FOR BLANKS!!! Won't happen ever time, but occasionaly will ssend the pyrodex pellet shooting off like a roman candle.