Last year, a friend bought her son a Beartooth Magnum .50 caliber and asked me to help the boy work up a load. I was pleased that the rifle tuned in very fast. We found it shot some 245 grain Aero Tip powerbelts very well with 85 grains of powder. It also shot 240 grain XTP's real good. We only has to worry about a 50 yard max range because of where he hunts. He later shot his deer with a Powerbelt at about 30 yards (as I remember) and it knocked it flat with the 85 grain load.

All you can do is get out and try some different loads.. Good luck with your rifle.