Burned plastic in my shotgun barrels.
I don't know about APP, as I only use the real, organic, original, true BP!
However, with BP, it does burn hot enough to melt the plastic wads and foul the barrel. However, it always cleaned out pretty easily with moose milk. That would be about a 10:1 dilution of Ballistol with water. I spray the barrels good, let them sit a couple of minutes, then wrap a cleaning patch around a bore brush. I then spray the patch with moose milk and run down the bore. Two or three patches like that would normally clean the bore quite well. I'd then finish with a pull of a bore snake and then a patch with straight ballistol. My bores stayed bright and shiny.