I agree with the advise to get a muzzle brake done professionally for the stated reasons. That said, if you want to use this rifle this fall for hunting, You could use a slip-on recoil pad until after the season to make shooting more tolerable. I shot probably over 500 rounds through an un-braked 300 RUM Sendero with one and it greatly helped. One cool breezy afternoon I put about 50 rounds through it and could have easily put 50 more through. It lengthened my LOP, but it wasn't a problem and I'm a short guy. You could take it off in the field for hunting. I usually never feel recoil when pulling the trigger on a game animal.
All that said, my new 300 RUM is wearing a muzzle brake and I'm liking it. One thing though... since it is a factory sporter, I would hesitate spending the $$$ to put a brake on it until I know it can shoot.
Pachmayr Recoil Pad Slip-On Rubber