My primary concern would be my hearing and the blast the brake would make towards others near me.
As it is I am nearly deaf. I have magnums too and I don't want a muzzle brake.
Make sure your rifle has a soft recoil pad such as the Decelerator and hold the rifle with both hands when you shoot it at the bench.
Long ago the 7mm RM was developed because a outfitter/smith found that the most gun his clients could shoot well was a 7mm Magnum.
Also consider loading the 300 down, selling it, getting a 7mm Magnum or even a 270!
