Snuffy, I don't know about plastic fouling in a muzzleloader, but Ballistol gets out lead and copper quite well, and does a good job on wad fouling in my modern shotguns. It has a lot more uses than that also. To my way of thinking, it's better to buy 1 do-it-all product that works as well as the specialty products, than it is to buy several different specialty products.