My oldest cartridge rifle is from 1863 and i have shot black powder rifles the past 35+ years.One thing i can say for certain is that leading is due to insufficient lubing not bad bore!!!Lead will rub off on steel and theres nothing you can do about it. Tin is to some extent and zink 100% self lubricating, but theres no pixie dust!Lube will cure all your ailments!I have a Marlin 1894 in 44 Magnum that has shot more than 5000+ shots at above 1750fps with lead bullets and it has still to see it's latest cleaning patch!Oh and that's the dreaded microgroove barrel "notorious" for leading.No pixie dust just proper bullet fit in the barrel and decent lube.