Colt IAR6940
A lightweight contender in the USMC IAR program.
The Colt IAR6940, also called the Colt Infantry Automatic Rifle or simply the Colt IAR, is a light machine gun chambered in 5.56×45mm NATO. Phil Hinckley designed it, and Colt manufactured it.
The weapon was built for the United States Marine Corps’ Infantry Automatic Rifle program. That program aimed to replace the M249 Squad Automatic Weapon with a lighter, more portable automatic rifle for individual Marines. Colt entered two variants into the competition: the IAR6940 and the IAR6940H. The IAR6940 weighed 10.1 lb, partly because it used a monolithic upper receiver. The IAR6940H weighed 9.28 lb, using a lighter Knight’s Armament handguard instead. Both models met the Marine Corps’ specifications and reached the finals, but Heckler & Koch’s M27 IAR won the contract. The Colt IAR never saw widespread U.S. military service. It was released to the civilian market in 2017, with only 200 units made by the U.S. Armament Company.
The IAR6940 is a magazine-fed, gas-operated, air-cooled weapon that uses a closed bolt and direct impingement, similar to the CAR-15. It accepts standard AR-15 magazines, including STANAG, PMAG, and drum types. It weighs 4.32 kg, compared to the M249’s 7.5 kg, and measures 934 mm with the stock extended. The gas regulator can be adjusted to change the rate of fire between 700 and 1,000 rounds per minute. Military models offer select-fire capability between semi-automatic and full automatic.
The upper receiver is monolithic, with the handguard integrated. It features a full-length Picatinny rail on top and two shorter rails on each side of the handguard, with venting along the top. Other upper receiver features—forward assist, cartridge deflector, and ejection port cover—are similar to M4/M16-type rifles. A large heat sink sits on the lower handguard to delay cook-off during sustained fire. The handguard can accept grip attachments. Most configurations include a Grip Pod, a vertical foregrip with an integrated bipod. The bolt assembly, charging handle, and bolt carrier group are identical to the M4’s. The lower receiver is functionally similar to the M4’s but adds an ambidextrous fire selector and magazine release. The rear uses an H3 buffer tube, compatible with most AR stocks, and comes standard with a VLTOR E-Mod stock.
The barrel is 16 inches long, internally chrome-plated, with a 1/7 right-hand parabolic twist.
Quick Facts
- Origin
- United States
- Is Ranged
- Yes
- Service
- 2010–present
- Designer
- Phil Hinckley
- Design Date
- 2008
- Manufacturer
- Colt's Manufacturing Company
- Weight
- 6940 & 6940E-SG unloaded: 4.32 kg (9.52 lb) · 6940 & 6940E-SG loaded (30-round STANAG): 4.95 kg (10.91 lb) / 6940H unloaded: 4.58 kg (10.1 lb) / 6940H loaded (30-round STANAG): 5.21 kg (11.49 lb)
- Length
- 851 mm (33.5 in) stock retracted, / 934 mm (36.8 in) stock extended
- Part Length
- 406 mm (16 in)
- Cartridge
- 5.56×45mm NATO
- Caliber
- 5.56 mm (0.22 in)
- Action
- Gas Operated, Rotating bolt
Facts from the source article.
Lore & Background
The IAR6940 was submitted by Colt Defense to the United States Marine Corps IAR Program, which began on March 27, 2008, when the USMC issued a Purchase Description outlining requirements. The program aimed to replace the M249 SAW with a single-infantry marine-operated automatic rifle that prioritized lightweight and ease of portability to enhance dismounted maneuverability. Colt submitted two variants: the IAR6940 and the lighter IAR6940H, which used a Knight's Armament Handguard. Both met the desired specifications and reached the finals, but ultimately lost to Heckler & Koch's M27 IAR.
The IAR6940 is a magazine-fed, gas-operated, air-cooled light machine gun using direct impingement similar to the CAR-15. It fires the 5.56×45mm NATO cartridge and accepts AR-15 magazines, including STANAG, PMAG, and drum magazines. The weapon features a monolithic upper receiver with a full-length Picatinny rail, a large heat sink on the lower handguard to delay cook-off, and a Grip Pod for stability. The lower receiver is functionally similar to the M4's but includes an ambidextrous fire selector and magazine release. The barrel is 16 inches long with chrome-plating and progressive 1/7 right-hand parabolic twist rifling, and it includes a bayonet stud and compensator.
Despite losing the USMC contract, the IAR6940 was released to the civilian market in 2017 in very low quantity—only 200 units by the U.S. Armament Company. It saw adoption by the Naval Infantry Corps of the Mexican Navy in 2010, and in 2024 it was introduced to the Singapore Armed Forces as the IAR6940E-SG, replacing the Ultimax 100. The Los Angeles County Sheriff's Department also uses the weapon.
Reader's Guide
The Colt IAR6940's significance lies in its role as a finalist in the USMC IAR Program, a high-profile competition that sought to modernize the Marine Corps' squad automatic weapon. Although it lost to the M27 IAR, the IAR6940 demonstrated the viability of a lightweight, magazine-fed automatic rifle based on the AR-15 platform. Its design emphasized portability and reduced weight—4.32 kg compared to the M249's 7.5 kg—while retaining select-fire capability and a rate of fire adjustable between 700 and 1000 rounds per minute. The weapon's legacy includes limited civilian sales and adoption by military forces outside the United States. The Mexican Naval Infantry Corps began using it in 2010 during the drug war, and the Singapore Armed Forces adopted a customized variant, the IAR6940E-SG, in 2024 to replace the aging Ultimax 100. The IAR6940 also saw use by the Los Angeles County Sheriff's Department. Its monolithic upper receiver, heat sink, and compatibility with standard AR-15 magazines made it a practical design, though it never achieved widespread U.S. military service.
Did You Know?
- The IAR6940 was designed by Phil Hinckley and manufactured by Colt.
- It lost the USMC IAR program to Heckler & Koch's M27 IAR.
- Only 200 units were released to the civilian market in 2017.
- The IAR6940E-SG variant replaced the Ultimax 100 in the Singapore Armed Forces in 2024.
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