I haven't shot enough through my 45-120 BC to be an authority on the matter yet, but I'll share what I've learned so far. I've only shot XMP5744 and Triple 7, with and without gas checked bullets and with jacketed bullets. T7 is much cleaner burning than Pyrodex and I wouldn't want to rely on data obtained from shooting white powder loads after shooting T7 or any black powder substitute loads without cleaning, it doesn't take much, just a damp patch or 2 followed by a dry patch to get the bore clean. I would highly recommend using a card or grease cookie when shooting lead only bullets, I got some bore leading using 95gr of T7 in the 45-120 with hard cast 500gr bullets with no fiber cards which I forgot to load! No problems with the gas checked lead bullets with the T7 or the smokeless.