I might play with some different powders as my load in my 300 rum used retumbo, but I have quite a bit of rl25 that I might try.
Right now I'm using RL25 with both the 210 and 215. I was able to shoot some more this morning, working up in half grain increments. Started to see pressure signs at 75.5 grains RL25 @ ~2970 fps, and unfortunately did not find another sweet spot above the first group I shot at 73 grains. I'm going to try some H1000 next to change up the impulse. I've found with this gun that it will shoot just about anything to about 3/4 moa, but it's not dialed in until it's shooting around .3 moa.