Hi Chambero and welcome to Hunttalk.. I suggest you go shoot a rifle in 300 WSM before you consider adding a muzzle break.. The recoil is markedly less than even a 270 shooting a heavy bullet. You may find out you don't need one.
They are too LOUD...the noise is worse than the recoil in my opinion. I can handle shooting over and over, but I can only handle the noise for two or three shots.....I would go with the above posts and do without. There are a lot of recoil pads on the market that work very well.
I've got a KDF on a lightweight 300 wby, and really like. It is loud, so loud in fact that you can freeze a bull in his tracks just from the concussion it time to get off a follow up shot . Seriously, the 300 wsm doesn't kick too bad, so you probably won't need it.
I have also seen both of my friends who have muzzle brakes lose second shots at game because they dropped to a prone position (good) and the brake blew up snow or dust clouds that totally blocked their view. (In both cases, fortunately, the deer went down shortly thereafter but long enough later that each would have put a second shot in him if they hadn't been blinded.)
I also know of a guy that had a brand new truck that he took out hunting. He wouldn't take us down the less used trails b/c he didn't want his paint scratched. Well, we saw some elk in a glade across the canyon so he jumps out and decides to use the hood of his now turned off vehicle. He proceeds to pull the trigger and promptly blistered the nice paint job on his brand new truck b/c of teh muzzle brake flash.
My first 300 was an ultra light so I had them thread the end for a brake. I guess recoil does not bother me much but if you stock is the proper length of pull you will not feel as much.
I removed the brake and screwed on a target-crown
looking thing in its place. The 300 has a pac.pad but the new simms recoil pads are really better at absorbing recoil.
Just remember, Dont LOSE YOUR HEARING trying to keep from a little punched. If recoil is a problem borrow a larger caliber an shoot it a few times the the 300 will feel like a BB gun
I put a Limbsaver pad on my 7 mag and it eleminated my recoil problems. Before, five or six shots would leave my shoulder sore for a week, and last week I put twenty shots thru it and didn't feel it at all. I can now hit what I shoot at.