M16 Series

From top: M16A1, M16A2, M4A1, M16A4

The **M16 rifle**, officially designated *Rifle, Caliber 5.56 mm, M16*, is a United States military adaptation of the ArmaLite AR-15 rifle. The original M16 was a select-fire, 5.56×45mm rifle with a 20-round magazine.

In 1964, the M16 entered American military service and the following year was deployed for jungle warfare operations during the Vietnam War. In 1969, the M16A1 replaced the M14 rifle to become the U.S. military's standard service rifle. The M16A1 improvements include a bolt-assist, chrome plated bore and a new 30-round magazine. In 1983, the USMC adopted the M16A2 rifle and the U.S. Army adopted it in 1986. The M16A2 fires the improved 5.56×45mm NATO cartridge and has a new adjustable rear sight, case deflector, heavy barrel, improved handguard, pistol grip and buttstock, as well as a semi-auto and three-round burst only fire selector. Adopted in 1998, the M16A4 is the fourth generation of the M16 series. It is equipped with a removable carrying handle and Picatinny rail for mounting optics and other ancillary devices.

The M16 has also been widely adopted by other militaries around the world. Total worldwide production of M16s has been approximately 8 million, making it the most-produced firearm of its 5.56 mm caliber. The U.S. Army has largely replaced the M16 in combat units with the shorter and lighter M4 carbine, and the U.S. Marine Corps approved a similar change in October 2015.

## Variants

### AR-15

The prototype AR-15 rifle was designed by ArmaLite as a selective fire weapon for military purposes. Armalite sold the design to Colt due to financial difficulties. After some modifications, the rifle eventually became the US Army's M16 rifle.

The AR-15 is a lightweight, intermediate cartridge magazine-fed, air-cooled rifle with a rotating lock bolt, actuated by direct impingement gas-operation or long/short stroke piston operation. Its design splits the rifle into two major components: the lower receiver, containing the trigger and buttstock and the upper receiver, which contains the bolt and barrel. This approach allows modular replacement of components.

### M16

Variant originally adopted by the U.S. Air Force. This was the first M16 adopted operationally. This variant had triangular handguards, butt stocks without a compartment for the storage of a cleaning kit, a three-pronged flash suppressor, full auto, and no forward assist. Bolt carriers were originally chrome plated and slick-sided, lacking forward assist notches. Later, the chrome plated carriers were dropped in favor of Army issued notched and parkerized carriers though the interior portion of the bolt carrier is still chrome-lined. The Air Force continued to operate these weapons until around 2001, at which time the Air Force converted all of its M16s to the M16A2 configuration. The M16 was also adopted by the British SAS, who used it during the Falklands War.

* **M16A1:** The U.S. Army XM16E1 was essentially the same weapon as the M16 with the addition of a forward assist and corresponding notches in the bolt carrier. The M16A1 was the finalized production model in 1967. Various changes were made after numerous problems in the field. Cleaning kits were developed and issued while barrels with chrome-plated chambers and later fully lined bores were introduced. With these and other changes, the malfunction rate slowly declined and new soldiers were generally unfamiliar with early problems. The M16A1 is no longer in service with the United States, but is still standard issue in many world armies.

* **M16A2:** The development of the M16A2 rifle was originally requested by the United States Marine Corps as a result of the USMC's combat experience in Vietnam with the XM16E1 and M16A1. It was officially adopted by US Department of Defense as the "US Rifle, 5.56mm, M16A2" in 1982. The Marines were the first branch of the U.S. Armed Forces to adopt the M16A2 in the early/mid-1980s, with the United States Army following suit in the late 1980s. Modifications to the M16A2 were extensive. In addition to the new rifling, the barrel was made with a greater thickness in front of the front sight post, to resist bending in the field and to allow a longer period of sustained fire without overheating. The rest of the barrel was maintained at the original thickness to enable the M203 grenade launcher to be attached. A new adjustable rear sight was added, allowing the rear sight to be dialed in for specific range settings between 300 and 800 meters to take full advantage of the ballistic characteristics of the new SS109 rounds and to allow windage adjustments without the need of a tool or cartridge. The weapon's reliability allowed it to be widely used around the United States Marine Corps special operations divisions as well.
* **M16A3:** The M16A3 is a modified version of the M16A2 adopted in small numbers by the U.S. Navy SEAL, Seabee, and Security units. It features the M16A1 trigger group providing "safe," "semi-automatic." and "fully automatic" modes instead of the A2's "safe," "semi-automatic," and "burst."
* **M16A4:** The M16A4 is the fourth generation of the M16 series. It is equipped with a removable carrying handle and a full length quad Picatinny rail for mounting optics and other ancillary devices. The FN M16A4, using safe/semi/burst selective fire, became standard issue for the U.S. Marine Corps and is the current issue to Marine Corps recruits in both MCRD San Diego and MCRD Parris Island. Military issue rifles are also equipped with a Knight's Armament Company M5 RAS hand guard, allowing vertical grips, lasers, tactical lights, and other accessories to be attached, coining the designation M16A4 MWS (or Modular Weapon System) in U.S. Army field manuals.

### Compact Models

* **CAR-15:** The CAR-15 Carbine was a shortened version for situations where longer weapons could be unwieldy, such as aboard vehicles or helicopters. The only significant change from the M16 rifle was that the barrel was shortened to 15 inches (381 mm) in length, so that it ended just forward of the front sight base. Because of the shorter barrel, no bayonet mounting lugs were provided.
* **M4 Carbine:** The M4 carbine is a shorter and lighter variant of the M16A2 assault rifle. The M4 is a 5.56×45mm NATO, air-cooled, direct impingement gas-operated, magazine-fed carbine. It has a 14.5 in (370 mm) barrel and a telescoping stock. The M4 carbine is heavily used by the United States Armed Forces and is replacing the M16 rifle in most United States Army and United States Marine Corps combat units as the primary infantry weapon. The M4 is also capable of mounting the M203 grenade launcher. The distinctive step in their barrel is for mounting the M203 with the standard hardware. The **M4** is capable of firing in semi automatic and three-round burst (like the M16A2 and M16A4), while the **M4A1** is capable of firing in semi-auto and full automatic (like the M16A1 and M16A3).

* **CAR-15 Commando:** The Commando was not initially part of the CAR-15 Military Weapons System, but was added in 1966 in response to the US military's desire for a shorter M16 and the Model 607 SMG's inadequacies. In April 1967, the Army purchased 510 Colt 629 Commandos for use by troops assigned to the Military Assistance Command, Vietnam Studies and Observations Group, and designated them *XM177E2*. The Air Force adopted a similar model without the forward assist feature as the *GAU-5A/A*. Problems with range, accuracy, barrel fouling, and usage of tracer bullets continued to plague the XM177 series, and production of the Commando ended in 1970.

## Mashup Rules

The M16A2, M16A3, M16A4, and M4 Carbine each feature a three-round burst setting.  When used with the Burst Fire feat, it fires only three bullets instead of five and can be used with only three bullets in the weapon. This setting does not grant the ability to make burst fire attacks without the Burst Fire feat; if you use the setting without the feat, you make a normal attack and the extra two bullets are wasted. Because these weapons do not have the automatic rate of fire, they cannot be used to make autofire attacks.

The CAR-15 Commando grants a +2 circumstance bonus on Sleight of Hand checks made to conceal the weapon.