RL 22, or RL 25, H1000, Retumbo, 7828, N165. All good powders. Use a premium bullet, like a Partition, TSX, TBBC, A Frame. Check the websites for the various powder manufacturers, and pick up some freeby data. Some rifles can be a bit finiky what you feed them so tinker around a bit, I know 2 guys with 300RUM's and both like near opposite loads.
Have fun.