Hi,unless you use smokeless powder,all other substitutes and black powder will corrode the barrel, if you don't clean it after firing it, within a few days or so. The black powder leaves more of a gray powdery substance and the other substitutes leave more of the rust.( Please only use smokeless in smokeless approved gun barrels,they will blow up the barrel in a regular muzzleloader because of the pressures that build up).A friend of mine gave me a solution for a Quick cleaner that does a great job without taking the gun all a part to clean. it is 1/3 Murphy's oil soap , 1/3 hydrogen peroxide, 1/3 Iso propyl alcohol. put in an old spray bottle and spray on patches and run down bore several times, then follow up with clean patches until they come out with nothing on them ,this will keep barrels from rusting until you can do a more thorough cleaning.This will not harm your barrel.