I load his bullets for him, so your in luck. We spent alot of time developing this load and it may not shoot as good in your gun, but it has shot good in another .300 so who knows..
75gr Rel 22/CCI mag primers/bullet seated .015 off the lands. (He shoots a Browning and the bullets still fit in his clip, but just barely.)
We both use Leupold 4.5x14 with BDC's installed, and we have been shooting rocks out as far out as 1200 yards with great success. (I shoot a .300 UM)