What range are you interested in?
I shoot a TC Omega .50 with a .44 Hornady ribbed sabot and a .430 300 grain cast bullet. I use 90 grains of 3F Goex powder. I get excellent groups out to 150 yards. In our woods I do not have many shots over that range. Before I received the 300 grain bullet mold, I used the .44 hornady ribbed sabot and the Hornady 300 grain XTP with the same powder load.
Danaidh