A muzzle brake is useful when a shooter desires less recoil from a rifle; possible instances might include target shooting or zeroing a weapon. The brake disperses the expanding powder-gasses away from the rifle at the muzzle's sides, rather than at its front. An AR-15 has relatively little recoil, and almost no recoil when a muzzle brake is used.
Items you will need
Padded gun vise
Punch
Hammer
Propane torch
Gloves
Channel-locks
Unload the weapon completely. Remove the magazine and visually inspect the chamber to ensure no ammo is present.
Place the weapon into a padded gun-vise with the sights facing up. Lock down the vise.
Locate any roll pins on the brake near the sight. Some AR-15 muzzle brakes have pins.
Heat the brake with a propane torch for 30 seconds. This will expand the metal and make the pins easier to remove. It will also loosen any bolt adhesives that might have been used.
Place a punch onto the roll pin. Tap out the pin with a hammer.
Turn the brake counterclockwise to unscrew it from the rifle. Use gloves while twisting by hand. If you cannot twist it off by hand, pad the brake with a cloth and use channel-locks to remove it.