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I don't think you want a split or broken muzzle... (sorry, had to)
But if you'd like to brake the rearward motion cause by recoil, remember that the muzzle blast is directed, depending on the brake's design, to the sides making things annoying if not uncomfortable for the shooter next to you (when at the range, zero'ing yer scope, chrono'ing yer loads, etc)...
If you must have a brake, try a Google Images search ".308 muzzle brake". Look at each design. Open the webpage link associated with each image. You'll be better able to decide on the right brake for you. In my case, I learned that (after purchasing a single-chamber brake) I don't need a brake on a .308, especially with a heavier barrel.
If I were you I'd rather look into a good recoil pad (Limbsaver) and perhaps a suppressor depending on the laws in your state. Otherwise I'd simply "buy ammo, use up, repeat" to become more competent with my rifle combination. Good luck!
/my .02