M16A4 Rifle, now in production, features a performance identical to the M16A2. Physical differences between the two weapons include a removable carrying handle with an integral rail-mounting system on the M16A4. When the carrying handle is removed, any accessory device with a rail grabber, such as an optical sight, can be mounted on the weapon.  The M16A4 replaced the M16A2.

The M16A4, now standard issue for front-line U.S. Marine Corps and some U.S. Army units, replaces the combination fixed carry handle/rear iron sight with a MIL-STD-1913 Picatinny rail, allowing for the rifle to be equipped with a carry handle and/or most military and consumer scopes or sighting systems.[8] Most of the U.S. Marine Corps' M16A4s are equipped with a Knight's Armament Company M5 RAS handguard, allowing vertical grips, lasers, tactical lights, and other accessories to be attached. U.S. Army M16A4s also often feature the KAC M5 RAS. In U.S. Army Field Manuals, M16A4s fitted with the RAS are sometimes referred to as M16A4 MWS or Modular Weapon System. This model retains the 3-round burst mode of the M16A2.

Caliber:      5.56x45 mm NATO
Magazine capacity:     30 rounds
Weight without magazine:     7.5 lbs.
Overall length:     39.6 in.
Barrel Length:     20 in.
Method of operation:     gas
Muzzle velocity (M855/SS109):     3,100 ft/sec
Maximum range (M855/SS109):     3,600 meters