Model Variants (Including Prototypes)
M16A2 - Assault Rifle Form on which the M4 Carbine is base on.
M4 - Carbine Form; semi-automatic and three round burst fire.
M4A1 - Full automatic fire in place of three-round burst option.
M4 MWS (Modular Weapon System) - Addition of the Rail Adapter System (RAS); originally labeled/designated as "M4E2".
SOPMOD Block I - "Special OPerations Peculiar MODification"; for special forces use; M4A1 model with Rail Interface System kit by Knight's Armament Company; optional M203 40mm grenade launcher; leaf sight device; sound suppressor; laser/IR designator; night vision sight; reflex sight.
SOPMOD Block II - Proposed improved SOPMOD modelunder consideration.