The M4 Carbine is a shorter and lighter version of the M16A2 assault rifle, achieving 80% parts commonality with the M16A2. As with many carbines, it was meant to provide troops with an effective, shoulder-fired
weapon in lieu of pistols, such as the M9. Since the
weapon is shorter (and therefore lighter), it is handy and more convenient to carry than a full-length rifle. While this makes it a candidate for non-infantry troops (vehicle crews, clerks and staff officers) it has been used by US Special Operations Command (SOCOM) and others seeking a compact
weapon for close quarters combat.
The M4A1 was developed and is produced for the United States
government by Colt Firearms, who has an exclusive contract to produce the M4 family of weapons through 2009.
The M4A1 carbine, an improvement upon the M4 carbine intended for Special Operations use, features a fully-automatic
fire mode, a flattop NATO M1913-specification rail on
top of the receiver (for attachment of optics and other devices), and a detachable rail-mounted carrying handle. The M4A1 can be found in use in many US military units, including the U.S. Army Rangers, the elite Delta Force, U.S. Navy SEALs, and the United States Marine Corps Force Reconnaissance companies. Variants of the carbine built by different manufacturers are also in service with many other foreign special forces
unit, most notably UK's SAS and
Australia's SASR.
The M4A1 Carbine is specially favored by counter-
terrorist and special forces units because of its compactness and firepower that the rifle offers for close quarters combat (CQB). It is very useful in urban warfare. Although the M4 does not have as far an effective range as the longer M16, many military analysts consider engagement with a non-specialized small arm above a range of 300m to be unnecessary.
The Special Operations Peculiar Modification (SOPMOD) I M4A1 Kit was developed by USSOCOM for use with units under its jurisdiction. The kit features an M4A1 rifle, a Rail Interface System (RIS) handguard system developed by Knight's Armament Company (KAC), a shortened quick-detachable M203 grenade launcher and leaf sight, a KAC silencer, KAC rear back-up sight, an Insight Technologies AN/PEQ-2A visible laser/infrared designator, along with Trijicon ACOG, Reflex optics and a nightvision sight. This kit was designed to be configurable (modular) for various missions and the kit is in service right now with Special Operations units (though many soldiers have changed the Trijicon Reflex sight for M68 Aimpoint red dot sights and EOTech holographic sights).
A 2nd generation SOPMOD (now known as SOPMOD II) is currently under development, with many different manufacturers competing for a contract. Notable manufacturers include Knight's Armament Company and their URX II, ARMS and their Selective Integrated Rail (SIR) system, along with Lewis Machine &
Tool's Monolithic Rail Platform (MRP).
The M4/M4A1 5.56 mm Carbine is a gas operated, air cooled, magazine fed, selective rate, shoulder fired weapon with a collapsible stock. A shortened variant of the M16A2 rifle with a 36 cm barrel, the M4A1 provides the individual soldier operating in close quarters the capability to engage targets at extended range with accurate, lethal
fire. The original M4 Carbine had "semi" and three round burst
fire modes, while the M4A1 has "semi" and "auto" but no three-round burst. The M4A1 Carbine achieves over 80% commonality with the M16A2 Rifle and was intended to replace M3 .45 ACP submachine guns and selected M9 pistols and M16 rifle series (though this plan
may be changed with the development of the XM-29 OICW and the XM8 carbine with most
Army units.) It is capable of mounting the M203 Grenade Launcher.
I had to apologize for making this
definition so damn long.
