|(Part 1. AR15 - Part 2. M16 - Part 3. M4)|
The Colt M16 assault rifle is a lightweight, select-fire (Full-Auto / Semi Auto), 5.56 mm caliber, air-cooled, gas-operated, magazine-fed rifle, with a rotating bolt, actuated by direct impingement gas operation. It is constructed of steel, aluminum and composite plastics.
The M16 assault rifle was adopted as a standard weapon by the U.S. Army in 1967. The M16 superseded the M14 rifle. The M16 fires 5.56 millimeter (.22" caliber) ammunition at the rate of 700–950 rounds per minute. These rifles will fire the 5.56x45 NATO cartridge and the 223 Remington commercial cartridge as well.
The M16 Rifle family including the M16A1, M16A2, M16A3 and M16A4 has been the primary infantry rifle of the United States military since the 1960s, is in use by 15 NATO countries, and has been the most produced firearm in its caliber.
The M16A1 was simply the M16 with a forward assist as requested by the Army. This weapon remained the primary infantry rifle of the United States military from 1967 until the 1980s, when it was supplemented by the M16A2.
The M16A2 entered service in the 1980s and fired the NATO standard 5.56 NATO round. The M16A2 is a select fire rifle capable of semi-automatic or three-round bursts and incorporating design elements desired by the Marine Corps. These features included an adjustable rear-sight for windage and elevation, a 5/8 inch longer buttstock, heavier barrel, case deflector for left-handed shooters, and rounded handguards. Mode of fire is determined by using a selector switch on the side of the weapon.
The M16A3 was essentially an M16A2 with an M16A1 fire control group. The M16A3 is a fully-automatic variant of the M16A2, issued primarily within the United States Naval Special Warfare. The M16A2, in turn, is currently being supplemented by the M16A4, which incorporates the flattop receiver unit developed for the M4 Carbine. Previous versions of the weapon are still in stock and used primarily by reserve and National Guard units in the United States as well as by the U.S. Air Force.
The M16A4 became standard issue for the United States Marine Corps during Operation Iraqi Freedom, increasingly replacing the earlier M16A2. In the United States Army, a combination of the M16A4 and M4 Carbine continue to replace existing M16A2 Rifles. The A4 incorporates a flattop receiver unit developed for the M4 Carbine. The USMC version of the M16A4 features a handguard with four Picatinny rails for mounting optical sights, laser pointers, night vision, forward handgrips, removable carry handle and flashlights.