I have been shooting black powder loads for years and the times where I've had plastic fouling occurred only when I used a plastic hull. The plastic comes from the heat of the powder melting the hull and does leave a lot of it in the bores. Cowboy action shooters can push out a snake of plastic when cleaning after an event. I've done this myself on occasion. When I load for a nice vintage gun I use paper hulls. Federal once fired or new Cheddite hulls for the 12 ga. I laid in 2 flats of RST 16ga paper loads just to have the paper hulls on hand to reload. Check with them and see if and when they will have them in stock. With black powder, a thick nitro card followed with a lubed fiber or lubed felt wad stack and a thin over shot card and a plastic shotcup, I have never experienced plastic build up. Guns clean up easily and the tubes are clean with no plastic residue. I am sure the plastic fouling is coming from the hulls rather than the shotcups. On a clay's course I do "cheat" a bit and after 4 stations I shoot a pair of smokeless loads just to clean out the fouling in the tubes and carry on. 50 + shells with black powder is just a bit much without any cleaning and the fouling would be very heavy. 16 and burning out the crap works very well and would probably keep the gun shooting all day long. Last time out I used Cheddite primed new paper hulls with 90 grains of old GOEX 1 fg. nitro card, 2 lubed felt wads, overshot card, plastic shot cup, 1oz #7.5, overshot card and a roll crimp. Crushed birds and cleaned up without any problems.
