Introduction:
The M16 is a lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed assault rifle, with a rotating bolt, actuated by direct impingement gas operation. The rifle is made of steel, aluminum, composite plastics and polymer materials.
The U.S. Air Force's rifle, the M16, and the United States Marine Corps and Army rifle, the XM16E1, were the first versions of the M16 rifle fielded. Soon, the Army standardized the XM16E1 as the M16A1 rifle, an M16 with a forward assist feature requested by the Army. All of the early versions were chambered to fire the M193/M196 cartridge in the semi-automatic and the automatic firing modes. This occurred in the early 1960s, with the Army issuing it in late 1964. Commercial AR-15s were first issued to Special Forces troops in spring of 1964.
A U.S. soldier on NBC exercise, holding an M16A1 rifle and wearing an M40 Field Protective Mask. Note the receiver, forward assist and the barrel flash suppressor.
The M16A2 rifle entered service in the 1980s, chambered to fire the standard NATO cartridge, the Belgian-designed M855/M856 cartridge. The M16A2 is a select-fire rifle (semi-automatic fire, three-round-burst fire) incorporating design elements requested by the Marine Corps: an adjustable, windage rear-sight; a stock 5/8-inch longer; heavier barrel; case deflector for left-hand shooters; and cylindrical hand guards. The fire mode selector is on the receiver's left side. The M16A2 is still the primary rifle in the U.S. Navy, Coast Guard, Air Force, and still is in heavy use in the Army and Marine Corps.
The M16A4 rifle was standard issue for the United States Marine Corps in Operation Iraqi Freedom; it replaced the M16A2 in front line units. In the U.S. Army the M16A2 rifle is being supplemented with two rifle models, the M16A4 and the M4 carbine as the standard issue assault rifle. The M16A4 has a flat-top receiver developed for the M4 carbine, a handguard with four Picatinny rails for mounting a sight, laser, night vision device, forward handgrip, removable handle, or a flashlight.
The M16 rifle is principally manufactured by Colt and Fabrique Nationale de Herstal (under a U.S. military contract since 1988 by FNH-USA; currently in production since 1991, primarily M16A2, A3, and A4), with variants made elsewhere in the world. Versions for the U.S. military have also been made by H & R Firearms General Motors Hydramatic Division most recently by Sabre Defence. Semi-automatic versions of the AR-15 are popular recreational shooting rifles, with versions manufactured by other small and large manufacturers in the U.S.
History:
Summary
The AR-15 was first adopted in 1962 by the United States Air Force, ultimately receiving the designation M16. The U.S. Army began to field the XM16E1 en masse in 1965 with most of them going to the Republic of South Vietnam, and the newly organized & experimental Airmobile Divisions, the 1st Air Cavalry Division in particular. The U.S. Marine Corps in South Vietnam also experimented with the M16 rifle in combat during this period. The XM16E1 was standardized as the M16A1 in 1967. This version remained the primary infantry rifle of U.S. forces in South Vietnam until the end of the war in 1975, and remained with all U.S. military ground forces after it had replaced the M14 service rifle in 1970 in CONUS, Europe (Germany), and South Korea; when it was supplemented by the M16A2. During the early 1980s a roughly
standardized load for this ammunition was adopted throughout NATO (see: 5.56x45mm NATO).
The M16A3 is a fully-automatic variant of the M16A2, issued within the United States Navy. The M16A2 is currently being supplemented by the M16A4, which incorporates the flattop receiver unit developed for the M4 carbine, and Picatinny rail system. M16A2s are still in stock with the U.S. Army and Marine Corps, but are used primarily by reserve and National Guard units as well as by the U.S. Air Force.
Design details:
The M16's receivers are made of aluminium alloy, its barrel, bolt, and bolt carrier of steel, and its handguards, pistol grip, and buttstock of plastics. Early models were especially lightweight at 6.5 lb (2.9 kg) without magazine and sling. This was significantly less than older 7.62 mm "battle rifles" of the 1950s and 1960s. It also compares with the 6.5 lb (2.9 kg) AKM without magazine. M16A2 and later variants weigh more (8.5 lb (3.9 kg) loaded) because of the adoption of a thicker barrel profile. The thicker barrel is more resistant to damage when handled roughly and is also slower to overheat during sustained fire. Unlike a traditional "bull" barrel that is thick its entire length, the M16A2's barrel is only thick forward of the handguards. The barrel profile under the handguards remained the same as the M16A1 for compatibility with the M203 grenade launcher. The rifle is the same length as the M16A2.
One distinctive ergonomic feature is a plastic or metal stock directly behind the action, which contains a recoil spring. This serves the dual function of operating spring and recoil buffer.The stock being in line with the bore reduces muzzle rise, especially during automatic fire. Because recoil does not significantly shift the point of aim, faster follow-up shots are possible and user fatigue is reduced.
Another distinctive ergonomic feature is a carrying handle on top of the receiver, with an integrated rear sight assembly and charging handle. This design is a by-product of the original design where the carry handle served to protect the charging handle and mount a scope. In practice, the handle is rarely used to carry the weapon and doing so is expressly prohibited in many military organizations, as it is considered unsafe.[citation needed] Holding the weapon by the pistol grip provides quicker response time and better "muzzle awareness," while a shoulder sling provides a more convenient option when response time is not a concern. More importantly, with the sight plane 2.5 in (63.5 mm) over the bore, the M16 has an inherent parallax problem that can be confounding to shooters. At closer ranges (typically inside 15–20 meters), the shooter must aim high in order to place shots where desired.
Newer models have a "flattop" upper receiver with a Picatinny rail, to which the user can attach either a conventional sighting system or numerous optical devices such as night vision scopes.
The M16 utilizes direct impingement gas operation; energy from high-pressure gas tapped from a non-adjustable port built into the front sight assembly actuates the moving parts in the weapon. Combustion gases travel via a gas tube above the barrel directly into a chamber in the bolt carrier behind the bolt itself, pushing the carrier away from the bolt. This reduces the number of moving parts by eliminating the need for a separate piston and cylinder and it provides better performance in rapid fire by keeping reciprocating masses on the same axis as the bore.
The primary criticism of direct impingement is that fouling and debris from expended gunpowder is blown directly into the breech. As the superheated combustion gas travels down the tube, it expands and cools. This cooling causes vaporized matter to condense as it cools depositing a much greater volume of solids into the operating components of the action. The increased fouling can cause malfunctions if the rifle is not cleaned as frequently as should be. The amount of sooting deposits tends to vary with powder specification, caliber, and gas port design.
Production and users:
The M16 is the most commonly manufactured 5.56x45mm rifle in the world. Currently, the M16 is in use by 15 NATO countries and more than 80 countries world wide. Together, numerous companies in the United States, Canada, and China have produced more than 8,000,000 rifles of all variants. Approximately 90% are still in operation. The M16 replaced the M14 and M1 carbine as standard infantry rifles of the U.S. armed forces. The M14 continues to see limited service, mostly in sniper, designated marksman, and ceremonial roles.
The M16 is a lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed assault rifle, with a rotating bolt, actuated by direct impingement gas operation. The rifle is made of steel, aluminum, composite plastics and polymer materials.
The U.S. Air Force's rifle, the M16, and the United States Marine Corps and Army rifle, the XM16E1, were the first versions of the M16 rifle fielded. Soon, the Army standardized the XM16E1 as the M16A1 rifle, an M16 with a forward assist feature requested by the Army. All of the early versions were chambered to fire the M193/M196 cartridge in the semi-automatic and the automatic firing modes. This occurred in the early 1960s, with the Army issuing it in late 1964. Commercial AR-15s were first issued to Special Forces troops in spring of 1964.
A U.S. soldier on NBC exercise, holding an M16A1 rifle and wearing an M40 Field Protective Mask. Note the receiver, forward assist and the barrel flash suppressor.
The M16A2 rifle entered service in the 1980s, chambered to fire the standard NATO cartridge, the Belgian-designed M855/M856 cartridge. The M16A2 is a select-fire rifle (semi-automatic fire, three-round-burst fire) incorporating design elements requested by the Marine Corps: an adjustable, windage rear-sight; a stock 5/8-inch longer; heavier barrel; case deflector for left-hand shooters; and cylindrical hand guards. The fire mode selector is on the receiver's left side. The M16A2 is still the primary rifle in the U.S. Navy, Coast Guard, Air Force, and still is in heavy use in the Army and Marine Corps.
The M16A4 rifle was standard issue for the United States Marine Corps in Operation Iraqi Freedom; it replaced the M16A2 in front line units. In the U.S. Army the M16A2 rifle is being supplemented with two rifle models, the M16A4 and the M4 carbine as the standard issue assault rifle. The M16A4 has a flat-top receiver developed for the M4 carbine, a handguard with four Picatinny rails for mounting a sight, laser, night vision device, forward handgrip, removable handle, or a flashlight.
The M16 rifle is principally manufactured by Colt and Fabrique Nationale de Herstal (under a U.S. military contract since 1988 by FNH-USA; currently in production since 1991, primarily M16A2, A3, and A4), with variants made elsewhere in the world. Versions for the U.S. military have also been made by H & R Firearms General Motors Hydramatic Division most recently by Sabre Defence. Semi-automatic versions of the AR-15 are popular recreational shooting rifles, with versions manufactured by other small and large manufacturers in the U.S.
History:
Summary
The AR-15 was first adopted in 1962 by the United States Air Force, ultimately receiving the designation M16. The U.S. Army began to field the XM16E1 en masse in 1965 with most of them going to the Republic of South Vietnam, and the newly organized & experimental Airmobile Divisions, the 1st Air Cavalry Division in particular. The U.S. Marine Corps in South Vietnam also experimented with the M16 rifle in combat during this period. The XM16E1 was standardized as the M16A1 in 1967. This version remained the primary infantry rifle of U.S. forces in South Vietnam until the end of the war in 1975, and remained with all U.S. military ground forces after it had replaced the M14 service rifle in 1970 in CONUS, Europe (Germany), and South Korea; when it was supplemented by the M16A2. During the early 1980s a roughly
standardized load for this ammunition was adopted throughout NATO (see: 5.56x45mm NATO).
The M16A3 is a fully-automatic variant of the M16A2, issued within the United States Navy. The M16A2 is currently being supplemented by the M16A4, which incorporates the flattop receiver unit developed for the M4 carbine, and Picatinny rail system. M16A2s are still in stock with the U.S. Army and Marine Corps, but are used primarily by reserve and National Guard units as well as by the U.S. Air Force.
Design details:
The M16's receivers are made of aluminium alloy, its barrel, bolt, and bolt carrier of steel, and its handguards, pistol grip, and buttstock of plastics. Early models were especially lightweight at 6.5 lb (2.9 kg) without magazine and sling. This was significantly less than older 7.62 mm "battle rifles" of the 1950s and 1960s. It also compares with the 6.5 lb (2.9 kg) AKM without magazine. M16A2 and later variants weigh more (8.5 lb (3.9 kg) loaded) because of the adoption of a thicker barrel profile. The thicker barrel is more resistant to damage when handled roughly and is also slower to overheat during sustained fire. Unlike a traditional "bull" barrel that is thick its entire length, the M16A2's barrel is only thick forward of the handguards. The barrel profile under the handguards remained the same as the M16A1 for compatibility with the M203 grenade launcher. The rifle is the same length as the M16A2.
One distinctive ergonomic feature is a plastic or metal stock directly behind the action, which contains a recoil spring. This serves the dual function of operating spring and recoil buffer.The stock being in line with the bore reduces muzzle rise, especially during automatic fire. Because recoil does not significantly shift the point of aim, faster follow-up shots are possible and user fatigue is reduced.
Another distinctive ergonomic feature is a carrying handle on top of the receiver, with an integrated rear sight assembly and charging handle. This design is a by-product of the original design where the carry handle served to protect the charging handle and mount a scope. In practice, the handle is rarely used to carry the weapon and doing so is expressly prohibited in many military organizations, as it is considered unsafe.[citation needed] Holding the weapon by the pistol grip provides quicker response time and better "muzzle awareness," while a shoulder sling provides a more convenient option when response time is not a concern. More importantly, with the sight plane 2.5 in (63.5 mm) over the bore, the M16 has an inherent parallax problem that can be confounding to shooters. At closer ranges (typically inside 15–20 meters), the shooter must aim high in order to place shots where desired.
Newer models have a "flattop" upper receiver with a Picatinny rail, to which the user can attach either a conventional sighting system or numerous optical devices such as night vision scopes.
The M16 utilizes direct impingement gas operation; energy from high-pressure gas tapped from a non-adjustable port built into the front sight assembly actuates the moving parts in the weapon. Combustion gases travel via a gas tube above the barrel directly into a chamber in the bolt carrier behind the bolt itself, pushing the carrier away from the bolt. This reduces the number of moving parts by eliminating the need for a separate piston and cylinder and it provides better performance in rapid fire by keeping reciprocating masses on the same axis as the bore.
The primary criticism of direct impingement is that fouling and debris from expended gunpowder is blown directly into the breech. As the superheated combustion gas travels down the tube, it expands and cools. This cooling causes vaporized matter to condense as it cools depositing a much greater volume of solids into the operating components of the action. The increased fouling can cause malfunctions if the rifle is not cleaned as frequently as should be. The amount of sooting deposits tends to vary with powder specification, caliber, and gas port design.
Production and users:
The M16 is the most commonly manufactured 5.56x45mm rifle in the world. Currently, the M16 is in use by 15 NATO countries and more than 80 countries world wide. Together, numerous companies in the United States, Canada, and China have produced more than 8,000,000 rifles of all variants. Approximately 90% are still in operation. The M16 replaced the M14 and M1 carbine as standard infantry rifles of the U.S. armed forces. The M14 continues to see limited service, mostly in sniper, designated marksman, and ceremonial roles.
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