M4 Carbine American 5.56mm Assault Rifle
M4
Assault Rifle
Other
Basic Information
Name
M4 Carbine American 5.56mm Assault Rifle
Designation
M4
Alternate Designation
—
Equipment Type
Assault Rifle
Manufacturer
Colt's Manufacturing Company, US Colt Canada in Ontario, Canada Lewis Machine and Tool Company in Milan, Illinois, US Bushmaster Firearms International, US U.S. Ordnance, US Remington Arms Company, US Daniel Defense in Black Creek, Georgia, US Lithgow Small Arms Factory, Australia Forjas Taurus São Leopoldo, RS, Brazil FN Herstal, Belgium. SME Ordnance, Malaysia Sarsilmaz, Turkey Caracal International, United Arab Emirates
Date of Introduction
1994
Description
Hezbollah Proliferation. The M4 carbine is a shorter and lighter variant of the M16A2 assault rifle. The M4 is a 5.56×45mm NATO, air-cooled, gas-operated, magazine-fed carbine. It has a 14.5 in (370 mm) barrel and a telescoping stock. The M4 carbine is extensively used by the United States Armed Forces and is largely replacing the M16 rifle in the United States Army and the United States Marine Corps combat units as the primary infantry weapon and service rifle. The M4 is also capable of mounting the M203 and M320 grenade launchers. The distinctive step in its barrel is for mounting the M203 with the standard hardware. The M4 has semi-automatic and three-round burst firing modes (like the M16A2 and M16A4), while the M4A1 has semi-automatic and fully automatic firing modes (like the M16A1 and M16A3).
Variants
Note
Except for the first delivery order, all U.S. military-issue M4 and M4A1 carbines possess a flat-top NATO M1913-specification (Picatinny) rail on top of the receiver for attachment of optical sights and other aiming devices—Trijicon TA01 and TA31 Advanced Combat Optical Gunsights (ACOG), EOTech 550 series holographic sights, and Aimpoint M68 Close Combat Optic (M68 CCO) being the favorite choices—and a detachable rail-mounted carrying handle. Standards are the Colt Model 920 (M4) and 921 (M4A1).
Variants of the carbine built by different manufacturers are also in service with many other foreign special forces units, such as the Australian Special Air Service Regiment (SASR). While the SASR uses weapons of essentially the same pattern built by Colt for export (Colt uses different models to separate weapons for the U.S. military and those for commercial/export purposes), the British SAS uses a variant on the basic theme, the Colt Canada (formerly Diemaco) C8SFW.
XM177
The XM177 was used in the military since 1965 until 1994 when it was replaced by the M4. The weapon, however, was at its prototype stage, and it was used as a testing weapon to see how it can be used in combat. The Colt 607 was its first model based on the XM16E1. However, it was referred to as the CAR-15 SMG. In 1966, Colt introduced the XM177, which was an improved variant of the CAR-15 Carbine. The Colt 609 was used by the US Army, the US Navy Seals, and the MACV-SOG, referred as the XM177E1. The USAF however used the Colt 610, which is referred to as the GAU-5A, which became known as the GUU-5P. The XM177E1 does have problems with weapon jamming, however it does have positive reviews, and some soldiers preferred the XM177 over the M16. Mainly because it was shorter, lighter, and easier to handle. In 1967, Colt adopted the Colt 629, which is known as the XM177E2. The XM177E2 has some improvements over the M16A1, and Is prone to jamming less than the older variants. The weapon quickly became a favorite of the MACV-SOG. In 1970, Colt stopped making the Colt Commando series, and in 1983, Colt start making a variant of the XM177E2 with some M16A2 features. The XM177E2 prototype was completely finished in 1993, and it became the M4.
M4 MWS (Modular Weapon System)
Colt Model 925 carbines were tested and fitted with the Knight's Armament Corporation (KAC) M4 RAS under the designation M4E2, but this designation appears to have been scrapped in favor of mounting this system to existing carbines without changing the designation. The U.S. Army Field Manual specifies for the Army that adding the Rail Adapter System (RAS) turns the weapon into the M4 MWS or Modular Weapon System.
M4A1
The M4A1 carbine is a fully automatic variant of the basic M4 carbine intended for special operations use. The M4A1 was introduced in May 1991 with improvements. and was in service in 1994. The M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger group, while the M4 has a "S-1-3" (safe/semi-automatic/3-round burst) trigger group. The M4A1 is used by almost all U.S special operation units including, but not limited to, Marine Force Recon, Army Rangers, Army Special Forces, Navy SEALs, United States Air Force Pararescue and Air Force Combat Control Teams. It has a maximum effective range of about 500 to 600 meters (550–660 yd). The fully automatic trigger gives a more consistent trigger pull, which leads to better accuracy. According to Mark A. Westrom, owner of ArmaLite, Inc., automatic fire is better for clearing rooms than burst fire.
In the last few years, M4A1 carbines have been refitted or received straight from the factory with barrels with a thicker profile under the handguard. This is for a variety of reasons such as heat dissipation during full-auto, and accuracy as a byproduct of barrel weight. These heavier barrel weapons are also fitted with a heavier buffer known as the H2. Out of three sliding weights inside the buffer, the H2 possesses two tungsten weights and one steel weight, versus the standard H buffer, which uses one tungsten weight and two steel weights. These weapons, known by Colt as the Model 921HB (for Heavy Barrel), have also been designated M4A1, and as far as the government is concerned the M4A1 represents both the 921 and 921HB.
Conversion of M4s to the M4A1 began in 2014, the start of all U.S. Army forces being equipped with the automatic variant. Though in service with special forces, combat in Afghanistan showed the need for providing automatic suppression fires during fire and movement for regular soldiers. The 101st Airborne Division began fielding new-built M4A1s in 2012, and the U.S. 1st Infantry Division became the first unit to convert their M4s to M4A1-standard in May 2014. Upgrades included a heavier barrel to better dissipate heat from sustained automatic firing, which also helps the rifles use the M855A1 EPR that has higher proof pressures and puts more strain on barrels. The full-auto trigger group has a more consistent trigger pull, whereas the burst group's pull varies on where the fire control group is set, resulting in more predictable and better accuracy on semi-automatic fire. Another addition is an ambidextrous selector lever for easier use with left-handed shooters. The M4-M4A1 conversion only increases weapon weight from 7.46 lb (3.38 kg) to 7.74 lb (3.51 kg), counting a back-up iron sight, forward pistol grip, empty magazine, and sling. Each carbine upgrade costs $240 per rifle, for a total cost of $120 million for half a million conversions. Three hundred conversions can be done per day to equip a brigade combat team per week, with all M4A1 conversions to be completed by 2019.
Mark 18 CQBR
The Mk 18 Close Quarters Battle Receiver is an M4A1 with a 10.3-inch barrel upper receiver. Current contractors for the Mark 18 are Colt and Lewis Machine & Tool (LMT) NSN 1005-01-527-2288.
Enhanced M4
For the Individual Carbine competition, Colt submitted their Enhanced M4 design, also known as the Colt Advanced Piston Carbine (APC). The weapon has a suppression-ready fluted barrel, which is lighter and cools better than previous M4 barrels. It is claimed to have "markedly better" accuracy. To improve reliability, Colt used an articulating link piston (ALP), which "reduces the inherent stress in the piston stroke by allowing for deflection and thermal expansion". In traditional gas piston operating systems, the force of the piston striking the bolt carrier can push the bolt carrier downwards and into the wall of the buffer tube, leading to accelerated wear and even chipped metal. This is known as carrier tilt. The ALP allows the operating rod to wiggle to correct for the downward pressure on the bolt and transfers the force straight backwards in line with the bore and buffer assembly, eliminating the carrier tilt. This relieves stress on parts and helps to increase accuracy. The Individual Carbine competition was canceled before a winning weapon was chosen.
M4 Commando
The modern Model 933 has a "flattop" receiver, with a removable carrying handle and a MIL-STD-1913 Picatinny rail, with semi-automatic and automatic fire. The Model 935 Commando has the features of the Model 933, but has three-round burst fire instead of automatic. Though originally called the M16A2 Commando, Colt markets them as the M4 Commando around 1995.
Armwest LLC M4
In 2014, American firearms designer Jim Sullivan provided a video interview regarding his contributions to the M16/M4 family of rifles when working for Armalite. A noted critic of the M4, he illustrates the deficiencies found in the rifle in its current configuration. In the video, he demonstrates his "Arm West LLC modified M4", with enhancements he believes necessary to rectify the issues with the weapon. Proprietary issues aside, the weapon is said to borrow features in his prior development, the Ultimax. Sullivan has stated (without exact details as to how) the weapon can fire from the closed bolt in semi-automatic and switch to open bolt when firing in fully automatic, improving accuracy. The weight of the cyclic components of the gun has been doubled (while retaining the weapon's weight at less than 8 pounds). Compared to the standard M4, which in automatic fires 750-950 rounds a minute, the rate of fire of the Arm West M4 is heavily reduced both to save ammunition and reduce barrel wear. The reduced rate also renders the weapon more controllable and accurate in automatic firing.
System
Alternate Designation(s)
M4
Type
Assault Rifle
Proliferation
Hezbollah
Date of Introduction
1994
Manufacturer
Colt's Manufacturing Company, US
Colt Canada in Ontario, Canada
Lewis Machine and Tool Company in Milan, Illinois, US
Bushmaster Firearms International, US
U.S. Ordnance, US
Remington Arms Company, US
Daniel Defense in Black Creek, Georgia, US
Lithgow Small Arms Factory, Australia
Forjas Taurus São Leopoldo, RS, Brazil
FN Herstal, Belgium.
SME Ordnance, Malaysia
Sarsilmaz, Turkey
Caracal International, United Arab Emirates
Proliferation
Widely Proliferated
Action
Gas-operated, rotating bolt, Stoner expanding gas
Rate of Fire
700–950 round/min cyclic
Muzzle Velocity
910 m/s
Effective Firing Range
500 m (550 yd)
Feed System
30-round box magazine or other STANAG magazines. Magazines with different capacities also available.
Sights
Iron sights or various optics
Dimensions
Length
838 mm
Length, Stock Collapsed
757 mm
Barrel Length
370 mm
Weight, Empty
2.5 kg
Ammunition
Type
Rifle
Caliber
5.56 mm
Cartridge
5.56x45 mm
Details
Country of Origin
United States
Category
Rifles
Land > Infantry Weapons > Rifles
Filter Label
M
Classification
Domain
Ground
Equipment Status
Active
Dimensions
Length
0.84 m
Width
—
Height
—
Weight
2.5 kg
Operators (59)
Russia
China
United States
France
Israel
Italy
Japan
Poland
Turkey
India
Pakistan
Brazil
Serbia
Afghanistan
Albania
Argentina
Australia
Bahrain
Bangladesh
Belize
Bolivia
Bosnia and Herzegovina
Canada
Colombia
Croatia
Dominican Republic
Ecuador
Egypt
El Salvador
Georgia
Ghana
Greece
Hungary
Indonesia
Iraq
Jamaica
Kenya
Kuwait
Lebanon
Liberia
Malaysia
Nepal
New Zealand
North Macedonia
Oman
Panama
Philippines
Portugal
Romania
Senegal
Singapore
Slovakia
Thailand
Tonga
Tunisia
Uganda
United Arab Emirates
Yemen
Non-State Actors
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