On the front of the cylinders on your originals you will see a bushing/gas ring. This protects the base pin from powder fouling. On the reproductions, including the S&W version, they have eliminated that bushing. As a result, the barrel/cylinder gap is directly in line with the base pin and fouling blows directly on the base pin every time you fire the gun. I had very poor luck with real BP. It is a little better with APP or 777, but still fouls fairly quickly. I'm not the type that's going to swab my rifle bore or shotgun bores or clean my handguns between every stage. If a gun/ammo combo won't reliably go at least six stages without attention, I correct the gun, the ammo, or both, or I find a different combination. I have an original and shooting BP or APP certainly won't hurt them. 777 probably won't either, but it has noticeably more grunt than real BP or APP so I haven't used it in my originals.