I just picked up my m&p 15-22 a couple days ago and I'm a bit of a newbie. How exactly would you install the brake on the barrel? Is it welded or threaded on? Would I need a gunsmith to do it?
Is your barrel threaded? If so & you already have the flash hider on it, then you can just turn it out yourself. You may want to get some 15-22 vice grips to make sure only the flash hider is moving around & not the barrel but I don't know from experience since I don't need to take mine off. Muzzle devices are typically only welded on with 14.5" barrels with a muzzle device making the over all length of it to 16".