"The 3rd generation of the M16 has been upgraded with a RIS (Rail Interface System) for mounting accessories and is capable of Automatic and Semi-Automatic fire. Available to front line units engaged in urban combat, the M16A3's low recoil makes a capable all around weapon."
— Battlelog description
The M16A3 is the standard assault rifle of the United States Marine Corps' Assault kit in Battlefield 3, filling in the same role as the AK-74M which is the Russian Ground Forces' starting assault rifle. It can later be unlocked for the Russian Ground Forces with 220,000 Assault points.
The M16A3 does the same damage as most Assault weapons. It possesses low kick, low spread, and a relatively high rate of fire. It is capable of rail-mounting either the M320 or the M26 MASS. The M16A3 tends to kick rightwards hard, so the Foregrip attachment is recommended to remedy this. When fitted with a non-magnifying optical sight such as a Reflex or Holographic Sight, the front iron sight is still visible on the weapon.
"This 4th generation M16A4 is equipped with a removable carring handle, a RIS (Rail Interface System) for mounting accessories, and is capable of both 3 Round Burst and Semi-Automatic fire. The original flaws of the M16 design have all but been eliminated and the M16A4 serves as the standard rifle of the USMC. Low recoil with a high rate of fire, the M16A4 is an accurate medium range weapon."
— Battlelog description
The M16A4 is the first burst-fire weapon unlocked. It is available for both factions at 89,000 Assault points.
Though aesthetically identical, the M16A4 differs from the M16A3 in a few notable ways, the foremost feature being its burst, semi-auto fire selector unlike the M16A3 which has a full auto, semi auto fire selector. As of patch 1.04, its stats differ from the M16A3. The M16A4 has only half the spread of the M16A3 when aiming down sights, making it much more viable as a long range weapon. The M16A4 also has tendency to kick rightwards, but not to an extent to M16A3. Still, Foregrip attachment is recommended to remedy this.
The M16A4 also possesses the semi-unique feature of sharing unlocks with the M16A3—otherwise only applicable to the M4 and M4A1. Any kills by the M16A3 or M16A4 total together so any unlocks received for the M16A3 will immediately be available to use on the M16A4 and vice versa.