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)

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".US Trademark serial number 76335060 registration number 2734001

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.

 References 

Category:5.56 mm firearms
Category:Assault rifles