I bought one of the early .50cal MK85's years and years ago, later converted it to 209 primers...gradually transitioned away from it to sidelock percussions, then flintlocks...but all I've ever used in all of them for almost 15 years is Natural Lube 1000...outstanding lube...this weekend I just pulled the MK85 from it's case after laying there untouched for four years and the bore is still like a mirror