The Colt IAR light machine gun / squad automatic weapon was developed by the famous American gun-making company Colt for the Infantry Automatic Rifle trials, initiated by the US Marine Corps in 2008. These trials, as announced, sought a lighter and a more maneuverable and reliable replacement for the M249 light machine gun, when used in the SAW / Automatic Rifle role. The USMC IAR trials were won by the HK 416 rifle, designed by the Heckler & Koch in Germany and adopted by the USMC as the M27 IAR. However, Colt decided to keep its own version of the Infantry Automatic Rifle, known as the Colt IAR Model 6940, as a production item. Circa 2010 Mexican Marines bought an undisclosed number of the Colt IAR machine guns for their units engaged in the fighting with the drug cartels, and after that there were no news about the Colt IAR until the spring of 2023. In April of 2023 the Ministry of Defense of Singapore announced that the Colt IAR would be adopted by the Singaporean military to replace old Ultimax 100 Mk.2 light machine guns in the Squad Automatic Weapon role. It is interesting to note that in the Singaporean trials the Colt IAR rifle apparently beat the HK 416 / IAR rifle, which also participated in the contest.
The Colt IAR light machine gun / squad automatic weapon is based on the Colt M4A1 carbine. It uses the M4A1 lower receiver with a select-fire trigger group that allows for single shots and continuous automatic fire, and fires from the closed bolt. It also uses the standard direct impingement gas operated action, the same as used in an AR-15, M16 and M4 rifles. The key difference between the Colt IAR and the M4A1 carbine is that the former has a much heavier and thicker barrel 16,1 inch long, which allows for more sustained fire capability. To further increase available volume of automatic fire before overheating, the barrel is provided with a massive heatsink / radiator, made of aluminum alloy. Most of its bulk is hidden inside a lower handguard. The upper receiver is of monolithic type, with the upper handguard made integral with the receiver to provide a single long Picatinny rail. Other features include a Vltor shoulder stock, and a proprietary folding front sight. The Colt IAR machine gun is compatible with most 5.56mm STANAG magazines, including various standard issue 20 or 30-round double stack box magazines, 60- and 100-round four stack box magazines and various drums that can hold up to 150 rounds of ammunition.
The Colt IAR light machine gun has no standard bipod; instead, a variety of supporting accessories can be attached to the Picatinny rail, integrated into the lower handguard. It also has a bayonet lug on the barrel, a feature very rarely seen on machine guns of any type.
It also must be noted that there were two other versions of the Colt IAR that never made it past the prototype stage. Those included a Colt IAR6940H with a different type of the heat sink / radiator, developed by the Knight’s Armament Co, and the Colt IAR6940P, an upper receiver with a short stroke piston instead of the more common direct impingement gas system.
Finally, it is worth noting that back around 2016 the Colt company sold a small number of Colt IAR upper receivers on the civilian market. Those upper receivers can be legally mounted onto any compatible semi-automatic mil-spec AR-15 lower receiver, or onto a compatible registered Class III select-fire AR-15 / M16 / M4 type lower receiver.
The Colt IAR light machine gun specifications: