MIL-DTL-32309, DETAIL SPECIFICATION: RIFLE, 5.56 MILLIMETER - M16A4 (05 AUG 2009)., This detail specification prescribes the requirements and identifies theverification procedures for the lightweight, air-cooled, gas operated, magazine-fed, 5.56millimeter (mm) weapon designed for either three shot automatic burst or semi-automatic fire,hereafter referred to simply as the weapon.