I know they make a foaming cleaner. Maybe try a few rounds of that. Good luck and keeps us informed.
I'd still try super hot water first. Its supposed to dissolve the harmful salts in the black powder residue. Ammonia might help too. It also works on cleaning some salts and metal oxidzes.@kev74 this is a inline BP takes a shotgun 209 primer .. breach plug missing .. but its full of funk from never being cleaned
You weren't kidding!Some dirty photos
That's a lot better!Some clean pics