As you get more fs the pressure goes up for the same wt(vol) of powder. If you are shooting conicals out of a 50 cal 100-150gs ff BP,Pyrodex or eq should do well. If 777, be sure to follow manfs instructions. Often 120-130gs will be about right. Don't go over the Manf's limit. If using pellets 100(2-50s) or 130(2 50s and 1 30) will often do better than 3 50s. The slight velocity increase is normally not that big of a deal. Often best accuracy/consistency is found with a carefully worked up load of Pyrodex P(a 3-f equavalent) . I'd start with 80-90gs with a 250g bullet such as a 250SST/SW. I've found 120-130gs has often been extremely accurate and fairly fast. So much depends on what gun you have. I'd tread much more lightly with a CVA,Traditions,Winchester that with a Knight,White,T/C,Savage, all of which have higher q/c IMO.
hpmuzzleloading.com has a lot of info on it.
Hope this helps.
PS: if you really want great performance, go to the smokeless section, read about them and consider getting a smokeless MLer. However, the non-smokeless MLers can provide great enjoyment and safety also.