M16 / AR15 Overview
One of the most popular automatic rifle designs to date, the M16 began life as the AR15 (Armalite Rifle) at the Armalite Division of the Fairchild Aircraft Corporation, designed by Eugene Stoner, Robert Fremont and James Sullivan.
The AR15 / M16 is actually the product of a scaled-down redesign of another Armalite rifle, the AR-10, a rifle designed during the mid-1950s to fire the full-power 7.62x51mm NATO cartridge. At the time, the AR-10 was unique in that was partially constructed of lightweight materials such as aluminum forgings and synthetic materials, which reduced weight substantially.
The USAF-sponsored “Project SALVO” opened the doors for a lightweight rifle of .22 caliber and low recoil, designed to increase the effectiveness of automatic fire. The AR-10 was then scaled down to accept a new cartridge, tentatively titled the .222 Special, and eventually sold commercially as the .223 Remington. The cartridge was classified as the 5.56x45mm M193 by the military. Resistance to this small-caliber concept from certain military elements and government entities led Armalite to sell rights to the AR-10 / AR15 design to Colt’s Patent Firearms Manufacturing Company in 1959.
Colt aggressively marketed the AR15 to militaries (as well as commercially), winning sizable US contracts which found the rifles type-classified as the M16 by the US Army. The rifles were then shipped to a small but growing conflict in Vietnam. During the Vietnam War, problems arose with the M16. Congressional inquiry into the matter found that the problems were due in large part to Army mismanagement (lack of training, incomplete testing of components prior to issue). With the addition of a slightly heavier barrel, a new flash suppressor, and a forward bolt assist, the rifle was officially adopted by the US Army in 1967 as the M16A1. Problems with the rifle quickly dissolved. Also during this time, an experimental, shortened version of the rifle, called the CAR-15, was put to use by special forces elements, nick-named the “commando”. Slight revisions landed it a type classification of XM177.
During the late part of the Vietnam War and into the late 1970s, NATO countries saw which way the wind was blowing and put some effort into developing other rifles and cartridges to improve the effectiveness of the 5.56x45mm cartridge. Fabrique Nationale developed a new bullet for the cartridge, designated internally as the SS109. This bullet led to the acceptance of the 5.56x45mm cartridge by NATO. The M16 was redesigned once again to maximize reliability for the new NATO cartridge (US M855), along with some improvements to the rifle, namely a heavier barrel, a new flash suppressor/compensator, and a new dual-aperture adjustable rear sight that represents a vast improvement over previous versions. The rifle was also restricted to three-round bursts instead of full-automatic fire in the interest of ammunition conservation. The rifle was officially type-classified as the M16A2 in 1982.
Several military elements had expressed interest in a version of the M16A2 for urban combat, somewhere in size between the M16A2 and the XM177 Commando. Colt developed the M4 Carbine, with a 14.5″ (368mm) barrel, step-cut to accept the M203 grenade launcher. By 1994, the M4, along with a full-automatic version of the M16A2 that included an integrated M1913 Picatinny Rail optics-mounting platform (M16A3), were also type-classified. Colt also shortened the M4 barrel another three inches and now markets the resulting carbine as the M4 Commando, a progression of the original XM177.
Development progressed with the M16 series rifles in the form of the SOPMOD (Special Operations Peculiar Modifications) program from the Naval Surface Warfare Center in Crane, Indiana. This program involves the addition of several aftermarket available parts and accessories for the M4A1 Carbine, maximizing effectiveness for special operations. This includes two sub-categories of the rifle, including the Special Purpose Rifle (SPR), an urban sniper platform, and the Close Quarters Battle Receiver (CQBR), yet another progression of the “commando” carbine.
There are now countless variations of the AR15 / M16 design, manufactured and sold by literally dozens of companies including Armalite, Bushmaster, Colt, Diemaco, DPMS, Fabrique Nationale, Les Baer Custom, Olympic Arms, Rock River Arms, Wilson Combat, and countless assembly companies. The M16 rifle is supported by a vast industry providing aftermarket parts, optics, and other accessories. This massive level of support suggests that the AR15 / M16 rifle is here for the forseeable future.