Try it, it wont hurt the revolver, just clean it good with soap and water dry it and oil it.
It adds flavor to the Cowboy shoots, The only problem using BP in the revolvers is the cylinder drag if the tolerance is to close between the cylinder and the cone. Load up a few, enough for a relay to see if you can get through with out fouling out. The old H&R's had enough clearance.
Fill the case full enough so the bullet base will touch it .
Kurt