I've used the 38/9mm hard rubber/plastic wadcutters primer powered for my cartridge powered guns as a garage practice and rat killer. They're very accurate at short ranges, although I did take a squirrel at 15yds with one, thought it would only scare it and bang flop. A friend with a 36cal b/p revolver tried some in his, using only caps and they worked, don't know about the accuracy, he's not a good shot with real bullets. Speer makes them and Midway had another brand that were hard rubber in assorted calibers, thye are reusable and a box of 100 lasted me a few years.