That's a real open question. I'm just going to assume you have an in line in .50 caliber because that's the norm. If that is the case then anything from 240 gr on up is fine. But you really have to see what shoots best out of your rifle. Most of my rifles like a 300 gr Hornady XTP in .44 cal (.429") and a Harvester green Crush Rib sabot.
But there are plenty of bullets out there. Find one your rifle shoots accurately.