Nancies
All subs are corrosive, except for the smokeless blackhorn of course.
You leave any sub in the barrel, pyro,t7,app. Its going to cause some kind of trouble like rust or pitting. Now lets not forget that the rifles you find that are all pitted to hell, these rifles 99.9 % of the time were first time amateurs who had no clue how to take care of the rifles or even how to shoot them and thats why you find them for sale in such poor condition.
Been using pyrodex in all of my muzzle loaders since i started with one and never had i had any issues with it in my rifles. Had my mountain stalker loaded with 80g pyrodex select for slightly over a month and it went boom right away and hit where it should have. No pitting or anything wrong down in the barrel.