You might try Ramshot Big Game. Their data shows 69.7 grains gets 2,827 fps with the Barnes 225 MRX. I know, not the exact same bullet but should be pretty close.
Then there is Ramshot Hunter which they show data for the 225 TSX, 74.8 grains max, giving 2,831 fps.
The IMR powder to try would be 4451. Hodgdon data shows a max load gives a velocity of 2,777.
I don't know- I think you might want to stick with the 4831. Even if you can gain 100 fps it's not going to provide a significant advantage in the real world.
