M4 carbine

The M4 carbine is a direct impingement, select fire carbine, chambered in 5.56 NATO. The M4 carbine is the main infantry rifle issued to the U.S. military and others around the world. The M4 family is a carbine offshoot of the M16 rifle. (A carbine is shorter than a rifle, longer than a pistol, and is usually fitted with an 11-18" barrel)

Carbine, 5.56 mm, M4
Colt M4 Carbine with ACOG Scope and a foregrip
Type	Assault rifle Carbine
Place of origin	United States
Service history
In service	1994–present
Used by	See Users
Wars	1998 Kosovo war War in Afghanistan (2001–14) War in Iraq (2003–2011) 2006 Lebanon war Mexican Drug War Gaza War 2010 Rio de Janeiro Security Crisis Colombian Armed Conflict Operation Enduring Freedom 2008 Russo-Georgian war Syrian civil war Battle of Arsal 2013 Lahad Datu standoff
Production history
Designed	1988–1994
Manufacturer	See Manufacturers
Unit cost	$700
Produced	1994–present
Variants	M4A1, CQBR (Mk. 18)
Specifications
Mass	6.36 lb (2.88 kg) empty 7.5 lb (3.4 kg) with 30 rounds
Length	33 in (840 mm) (stock extended) 29.75 in (756 mm) (stock retracted)
Barrel length	14.5 in (370 mm)
Cartridge	5.56×45mm NATO
Caliber	5.56 mm (.223 in)
Barrels	1
Action	Gas-operated, rotating bolt (Direct impingement)
Rate of fire	700–950 round/min cyclic
Muzzle velocity	2,900 ft/s (880 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

The M4 utilizes a Direct Gas Impingement system to cycle the action, meaning there is gas vented from the barrel, which travels through the gas tube, back into the upper receiver. This gas pushes the bolt carrier back which, consequently, discharges the fired cartridge, cocks the hammer, and reloads the chamber to fire the next round. The M4 is fitted with a 14.5 inch barrel, and is classified as an SBR. (Short Barreled Rifle) An SBR is a "pistol" fitted with a barrel shorter than 16", and is allowed to be fitted with a stock and vertical foregrip. The M4 family of rifles is chambered in the venerable 5.56 NATO round, the same round that the M16 family and AR-15 family of rifles fires.

The M4 can be fired in either the semi-automatic setting (one round fired per trigger pull), or the three-round burst setting ("burst fire" is the term used for the mechanical limitation of the full-auto function of the rifle from "full-auto" to firing up to three rounds when trigger is depressed). The M4A1 is the full-auto variant of the M4 . The carbine can be fitted with an M203 grenade launcher as well as the newer M320 grenade launcher. The M4 can be fitted with many accessories, such as night vision devices, silencers, PEQ boxes, telescopic sights, bipods, an under-barrel shotgun, and 1913 rail-mounted fore-grips.

The United States Marine Corps (USMC) has ordered its officers (up to the rank of lieutenant colonel) and non-commissioned officers to carry the M4 carbine instead of the M9 pistol. The M4 is also widely used by police officers, along with the AR-15. The M4 is widely used due to its low cost, low jamming, effeciveness at any range, and highly modifiable.

Trademark Information

The carbine was developed and produced for the United States government by Colt Firearms, which had an exclusive contract to produce the M4 family of weapons through 2009. Colt previously held a U.S. trademark on the term "M4".

Other manufacturers offer M4-like firearms. Many manufacturers have production firearms that look and function close to the M4. A civilian model is sometimes colloquially referred to as an "M4gery", a portmanteau word from "M4" and "forgery".

Colt said it held sole rights to the M4 name and design. Other manufacturers said that Colt was overstating its rights, and that "M4" was now a generic term for a shortened AR-15. On December 8, 2005, a District court judge ruled that "M4" was now a generic name, and that Colt's trademark should be revoked.