Enables attachment of M4FA or FA556AR suppressors to M4, M16/AR-15 with a barrel 12.5″ or longer, and to other 5.56mm (.223 cal.) semi-auto, bolt-action, or assault rifles with Mil-Spec 1⁄2−28 muzzle threads and (due to overlap design) first 2.75″ of barrel (measured from muzzle back) clear of obstructions and no more than .749″ in diameter. This adapter functions alone as a high-performance muzzle brake when the suppressor is removed. Patented design greatly diffuses side blast, counteracts up/right muzzle movement to keep muzzle on target, eliminates felt concussion on shooter. Heat-treated stainless steel construction.