My .50 cal flinter is the one that shoots the 370gr Maxi. They are lubed, and used without patch, paper, or sabot.
My old hunting partner had the Lyman mould for it and used pure lead from melted down sewer pipe. His creations are about .003" oversize compared to the prelubed factory made Maxi, and, in my flinter, will shoot about a 2" group @ 50yds with open sights the 1:48 twist, using 90 grs of Goex 2F. He purchased his moulds from Dixon's Muzzleloading shop in Kempton Pa.
As for performance on game, with very few exceptions, the deer react as if struck by lightning, provided the bullet placement is correct.