Then why are you useing plastic with your wads ? I've shot nitro and BP in my cartridge guns for 20 years. Been shooting muzzleloading smoothbores for 40 years and never used plastic wads. It's like putting a modern engine in a Model A. If you're loading equal amounts of powder and shot there will be no problem with any primer or hull. But please, throw away those plastic wads, they weren't made when BP was used in guns. Paul