I've never done it (powdercoat) myself, but I've shot a fair bit of black powder through a Ruger Old Army and other C&B revolvers. They shoot best when you use a slightly over-sized ball and shave a ring of lead off when seating. The bearing surface would be bare lead, but I've never gotten leading from them either. As Ian said, the lube will be required to keep fouling soft and prevent chain fires. Never had a chain fire, so it may or may not be for real, but I like lots of lube to keep things gooey until I clean it up.