M16 Variants
Colt AR-15
The civilian version of the M-16, called the AR-15, is a single-shot weapon manufactured by Colt. The Colt AR-15 is used by private citizens for everything from deer hunting to plinking at cans.
Any weapon which shoots automatically, more than one shot, without manual reloading, by a single function of the trigger, is a machinegun as defined in 26 U.S.C. 5845(b), the National Firearms Act (NFA). In addition, the definition of a machinegun also includes any combination of parts from which a machinegun may be assembled, if such parts are in possession or under the control of a person. An AR-15 type assault rifle which fires more than one shot by a single function of the trigger is a machinegun under the NFA. Any machinegun is subject to the NFA and the possession of an unregistered machinegun could subject the possessor to criminal prosecution. ATF has encountered various AR-15 type assault rifles such as those manufactured by Colt, E.A. Company, SGW, Sendra and others, which have been assembled with fire control components designed for use in M16 machineguns. The vast majority of these rifles which have been assembled with an M16 bolt carrier, hammer, trigger, disconnector and selector will fire automatically merely by manipulation of the selector or removal of the disconnector. Many of these rifles using less than these five M16 parts also will shoot automatically by manipulation of the selector or removal of the disconnector.
An assault weapon was defined under federal law as a semi-automatic [capable of being fired as fast as the operator can pull the trigger] assault pistol or rifle that can accept a detachable magazines and with two or more assault characteristics; or semi-automatic shotguns with two or more assault characteristics, including a pistol grip or thumbhole stock; folding stock or telescopic stock; flash suppressor or a threaded barrel capable of accepting a flash suppressor, bayonet mount, or grenade launcher.
The Colt AR-15 is a semiautomatic assault weapon as defined in the Gun Control Act of 1968. 18 U.S.C. 921(a)(30). Under this law it waa generally unlawful to possess or transfer these firearms. 18 U.S.C. 922(v)(1). This prohibition, however, did not apply to any AR-15 that was lawfully possessed on or before Sept. 13, 1994. 18 U.S.C. 921(v)(2). This 1994 federal assault weapons ban expired in September 2004, and with it the prohibition against selling this type of semiautomatic firearm.
M16A1 Semiautomatic Rifle
In 1967 the M16A1 was adopted by the US Army. It featured a positive forward assist to help close the bolt when dirty, chromium plated chamber and bore to resist corrosion and an improved gas system with a new bolt buffer designed to reduce the rate of fire on full auto. These improvements, together with a new field cleaning kit and better maintenance instruction, helped to get rid of the reliability problems.
Despite the problems encountered during initial fielding, better training, preventive maintenance, and several design changes, resulted in the weapon that has become the standard issue rifle of the US Army, with some 3,690,000 having been manufactured. The weapon, chambered for 5.56x45mm NATO caliber, has been a mainstay of the U.S. military ever since, and gradually replaced the M14 in U.S. service through the 1960's.
M16A2 Semiautomatic Rifle
The M16A2 semiautomatic rifle is the standard by which all military rifles of the future will be judged. This variant of the M16 fires a three-round burst in semiautomatic operation. The system incorporates an adjustable rear sight which corrects for both wind and elevation, a heavier barrel with 1-in-7 rifling, and a muzzle compensator to prevent muzzle climb during semiautomatic operation. The M16A2 is capable of firing all NATO standard 5.56mm ammunition and can fire 40mm grenades when equipped with the M203 Grenade Launcher.
The M16A2 replaced the M16A1 in U.S. Army service in 1983. It is essentially an improved M16A1. Major changes include: a switch from full automatic to 3-round burst capability; a heavier barrel; improved sights; new, stronger plastic buttstock, handguard, and pistol grip.The M16A2 has some practical features missing from the M16A1, found on the M4A1 -- the prime examples being the ability to rapidly breakdown the gun and fieldstrip, as well as the high metal parts content.
The M16A2 5.56mm rifle is a lightweight, air-cooled, gas-operated, magazine-fed, shoulder- or hip-fired weapon designed for either automatic fire (3-round bursts) or semiautomatic fire (single shot) through the use of a selector lever. The weapon has a fully adjustable rear sight. The bottom of the trigger guard opens to provide access to the trigger while wearing winter mittens. The upper receiver/barrel assembly has a fully adjustable rear sight and a compensator which helps keep the muzzle down during firing. The steel bolt group and barrel extension are designed with locking lugs which lock the bolt group to the barrel extension allowing the rifle to have a lightweight aluminum receiver.
The M16A2 rifle is a product improvement of the M16A1 rifle. The improvements are:
- a heavier, stiffer barrel than the barrel of the M16A1;
- a redesigned handguard, using two identical halves, with a round contour which is sturdier and provides a better grip when holding the rifle;
- a new buttstock and pistol grip made of a tougher injection moldable plastic that provides much greater resistance to breakage;
- an improved rear sight which can be easily adjusted for windage and range;
- a modified upper receiver design to deflect ejected cartridges, and preclude the possibility of the ejected cartridges hitting the face of a left-handed firer;
- a burst control device, that limits the number of rounds fired in the automatic mode to three per trigger pull, which increases accuracy while reducing ammunition expenditure;
- a muzzle compensator, designed to reduce position disclosure and improve controllability and accuracy in both burst and rapid semi-automatic fire;
- a heavier barrel with a 1 in 7 twist to fire NATO standard SS 109 type (M855) ammunition which is also fired from the M249 Squad Automatic Weapon (SAW). This further increases the effective range and penetration of the rifle cartridge. The M16A2 will also shoot the older M193 ammunition designed for a 1 in 12 twist.
M16A2 Squad Advanced Marksman Rifle [SAMR]
The Squad Advanced Marksman Rifle [SAMR] consists of the Trijicon Advanced Combat Optical Gunsight mounted on top of a M-16A2 with a match-grade heavy barrel and Harris bipod. It is an interim solution. Currently, Marine rifle squads have two sets of distinct weapons: three grenade launchers and three squad automatic weapons. If the experiment proves successful, they could get three SAMs as well. Some squads used SAMs for effective long-range shots against single targets. Others put SAMs in over-watch positions to cover a squad's movement to an objective, while some used them to scour avenues of approach, gathering on-scene intelligence. The scope, which has a unique reticle pattern with a red chevron for a 300-meter aiming point, also improved the ability to range targets at unknown distances. The chevron's upside-down V fits squarely over the shoulders of a man-sized target at 300 meters. The 400-, 500- and 600-meter bars just below the chevron also fits within the outer limits of a man's shoulders at that distance. Marines, shooting the M-16A2 with iron sights, had a first-shot hit rate of 45 percent on targets between 137 and 432 meters. With the SAMR, those rates were 88 percent.
M16A2E4 Semiautomatic Rifle
The M16A2E4 rifle is a standard M16A2 Rifle modified by changing the current upper receiver to a flat-top upper receiver with a detachable carrying handle. The flat-top upper receiver has an integral rail which is utilized (when the carrying handle is removed) to mount optical devices to the weapon. This integral rail has been designed to conform to MIL-STD 1913 and allows common mounting of many different items.
M16A3 Semiautomatic Rifle
The M16A3, which replace the M16A2 in 1994, is basically an M16A2 with full-automatic capability and optional M4A1-style Rail Interface System (RIS). The M16A3 and the M16A4 are identical to the M16A2, but both have the modular upper receiver. The M16A3 is capable of fully automatic fire, like the M16A1, while the M16A4 uses the M16A2's three-round burst mechanism. Additionally, several types of optical sights have been developed for the modular upper.
M16A4 Semiautomatic Rifle
The M16A4 is identical to the M16A3, but can fire single shots or 3-round bursts (no full auto). The M16A4 Rifle is a standard M16A2 Rifle with a flat top upper receiver and detachable carrying handle. The flat top upper receiver has an integral rail that will be utilized (when the carrying handle is removed) to mount optical devices to the weapon. The M16A4 Rifle in combination with the M5 Rail Adapter forms the Modular Weapon System (rifle version) which provide soldiers the flexibility to configure their weapons with those accessories required to fulfill an assigned mission. There are no differences between the internal dimensions of the M16A2 Rifle and the M16A4 Rifle.
