I'm shooting a .50 cal TC Renegade. I've shot 90 grains of FFF for years, but last year I swtiched over to 90 grains of 777. My bullet is a 240 Hornady XTP .44 mag in Sabot. 
Yeah I know, not so traditional huh?   Anyhow shot was about 80 yards and was perfect behind the shoulder, mid-body. Deer dropped in her tracks, tried to get up and that was all she wrote.
Last year I took one around 120 yards and it did the same thing.  I think the old flintlock pushes those XTP's at just the right velocity to do some major damage.  Just about every deer I shoot with this combo drop in their tracks.
Anyhow, more meet in the freezer