My close friend has a nice double .500 BPE. It shoots to the sights and is very accurate with 136gr. Pyrodex RS and a 450gr. Lyman bullet from an oversize mould. I don't think he's ever shot smokeless in it. Cleanup is easy. A 1/10" card over the powder is all, with a good black powder lube in the grooves - SPG or Lyman's BPGold work. With Pyrodex, even an Alox/beeswax lube might work.