The M16 rifle, officially designated Rifle, Caliber 5.56 mm, M16, is the United States military select-fire adaptation of the AR-15 rifle. The rifle was adapted for semi-automatic and full-automatic fire. Colt purchased the rights to the AR-15 from ArmaLite, and currently uses that designation only for semi-automatic versions of the rifle. SWAT officers in the director's cut of Lethal Weapon carry M16s with them as they enter the school grounds.
In the Director's Cut, SWAT officers are seen carrying MGC M16 Model Gun loaded with 30-round magazines. After Martin Riggs takes out the sniper, the SWAT officers armed with their M16s March into the school in case of other potential shooters being present.