IMR 4227 works best for me, tried SR4759 but things didn't group as well.
I'm using a modified NEI #185 375-310-GC but without the gas check shank so it casts out at about 286 grains. With 17 grains of 4227 it shoots under and inch at 100 yards. Velocity is about 1400 fps from a 30" barrel.