Being at rendezvous... the last thing ya want to hear is the guy loading the cannon/ mortar in the dark is " oh sh--!"40 years go we had a hard time getting 4F. We used it in mini replica cannons about the bore of a signal deck gun. Cannon BP sends out way too much hot and burning particles. Powder burn on my forehead took 20 years to clear up.
Last shot of the night, and last of the powder, an inch left in the barrel for packing... nobody yelled more powder after that one... they felt it!
Ryan