That's simply not true. Pyrodex is no worse than bp.
Really. What experience do you have to share?
Just saying:
My experiences. A young fellow came to me asking why his Traditions traditional wouldn't fire. I found enough pyrodex residue in his breech {I believe} which over time had built up to a point the residue plugged his rifles firing channel. Only tool that came to my mind to resolve? >the need of a breech scrapper.< as I've never encountered such a disappointing powder situation before.
Took my range rod and spun & spun that scrapper until I felt no resistance. A white powdery hardened ash like substance was removed from the breech area. Quite a bit of it. I actually saved all by pouring into a ash tray and too held some in the palm of my hand. Once removed. The rifle functioned as it should.
I informed the young feller and showed him the ash. I asked him what powder he was shooting?_ "No more Pyrodex RS goes down that barrel!!" so I was informed in less than a kindly way.
I've been shooting my B/P rifles since the mid 80s and not once have I had to use a barrel scrapper to clear my barrels breech of Gorex 2-FFG residue.
I've also been shooting homemade {screened B/P} going on three years. Pounds made and fired in my rifles and You know as well as I {screened only} B/P is perhaps the most fouling of all. But not once have I even found a need to scrap its fouling.
I'm highly suspect a cleaning will totally remove all Pyrodex fouling without a bore bristle brush. Especially ~when setting the rifle aside for a couple days before its barrel cleaning.
"Pyrodex use guarantee's the hardest fouling crud a shooter will ever encounter." No doubt about it!!!