First off, BP burns hotter than smokeless. It's an explosive, nitro isn't. Second, yes I've seen first hand the plastic residue left from plastic wads. I'm not talking a couple of shots to sight something in, or for hunting. My friend and I were shooting a birthday event, he BP, me nitro. It was a 150 shots. After about a hundred his gun started kicking harder. A little latter there were wiggly worms growing out of the end of his barrels. You could hardly see down the barrels they were so full. It took him about two hours to clean the barrels on his old SxS. Now, this was about 20 years ago. Maybe plastic wads are using different compounds now where they don't melt so easily, but why take the chance. It seems like many of you guys are just looking for the easy way out. Oh, I don't like the patterns. Or oh, I don't like the trouble it takes to load fiber wads. They don't cost sh!!, you can still make or buy them, and, it's the traditional way of loading BP shells.
So yes, I've had first hand experience with plastic and BP. Been doing it since 1970.