For 5.56 guns, my standard answer is an M16A1 flash hider. They are cheap, and work well. Your 300 is probably threaded 5/8x24, so the cheap A1/A2 option isn't there. I have a DSA three prong on mine. It works well, and the cost is reasonable. If you're looking to spend a lot of money, or want one of the designer muzzle brakes, I'm not the guy to ask.