Try RL 7 with the 350 Hornadies or Speer. I don't have my load notes handy and they were for the 458 lott but loaded to 458 win mag velocities. I was shooting a hair over moa using iron sights and original military triggers (Enfield and Mauser) Should be no problem getting MOA or better with a scope and decent trigger.
And my Lott's had long throats, I tried long loaded the 450 X bullet and could never touch the lands, and that's a long bullet.
