If you load the jacketed bullets, clean the bore of any residual copper fouling, then make sure all the Black Powder (BP) fouling is removed.
A few years ago, there was a thread on the Shiloh Sharps site about loading BP and jacketed bullets. Kirk, the owner, said that he once sectioned a pitted Shiloh barrel via the band saw. The owner loaded BP and jacketed bullets. The BP fouling became trapped beneath the copper fouling and pitted the barrel....