Many people shoot 3F in a .50, but I have always, for many, many years, used 2F in anything larger than .45.
: Contrary to most, I find 2F to shoot cleanly in all guns I use it in, including the .45 in years past. I also use tighter than normal combinatons of ball & patch than many people, it seems. The snug combinations help keep things clean, shot to shot.
: Oh yeah - forgot about the priming - I use 4F for priming as I find it faster than 3F. I see it is in vogue to say that there is no difference even down to 2F, but my friend and shooting companion with 35years of shooting Flinter's says 4F is faster in all his guns - and all are custom rifles and smoothbores with properly timed locks. The pan going off is about the same, but the actual main charge ignition is faster due to a hotter more violent flash - or so it seems that's the reason - even in the Brown Bess, 4F is faster.