I have used that bullet. It shoots real well in my Ruger Vacqueros. I have not shot it with black powder. I shoot it when I shoot with Trail Boss. (5.3 Grns). I tried pan lubing it, and the ran it through a lee .454 sizer, its kind of messy on the sizer, the sizer forced the Blk Pwdr lube into the shallow grooves. I don't think they would hold enough lube to keep the fowling soft, especially in a long gun. I like Blk Pwdr myself, It's more fun. I havn't shot the ones I pan lubed yet. The lube that comes on the bullets works good, with Trail Boss.
Not the answer you are looking for, but try pan lubing them, then run them thru a sizer, and try a few rounds.
Rebel Dave