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M27 Infantry Automatic Rifle News Photo 120322-M-PH863-005 - U.S. Marine Corps Lance Cpl. Leobardo Nunez provides security during a census patrol through a village near Khan Neshin Afghanistan on March 22.jpg
A U.S. Marine armed with an M27 fitted with a Harris bipod and a 3.5x SAW Day Optic covers his team in Afghanistan in March 2012.
Type * Squad automatic weapon
Place of origin  Germany
Service history
In service 2011–present
Used by United States United States Marine Corps
Wars Operation Enduring Freedom
Production history
Designer Heckler & Koch
Designed 2008
Manufacturer Heckler & Koch
Produced 2010–present
Number built 4,500 planned
Weight 7.9 lb (3.6 kg) empty
Length 36.9 to 33 in (940 to 840 mm) w/ adjustable stock
Barrel length 16.5 in (420 mm)
Width 3.1 in (79 mm)
Height 9.4 in (240 mm)

Cartridge 5.56×45mm NATO
Action Gas-operated short-stroke piston, rotating bolt
Rate of fire Sustained: 36 rpm
Cyclic: 700 to 850 rpm
Effective range 550 m (point target)
700 m (area target)[1]
Maximum range 3,938 yd (3,601 m)[1]
Feed system 30-round STANAG magazine
Sights 3.5x SAW Day Optic, flip-up rear rotary diopter sight and front post

The M27 Infantry Automatic Rifle (IAR) is a lightweight, magazine-fed 5.56mm weapon used by the United States Marine Corps. It is intended to enhance an automatic rifleman's maneuverability and displacement speed, and it is based on the HK416. The U.S. Marine Corps is planning to purchase 6,500 IARs to replace a portion of the M249 light machine guns currently employed by automatic riflemen within Infantry and Light Armored Reconnaissance Battalions. Approximately 8,000–10,000 M249s will remain in service at the company level to be used at the discretion of company commanders. The United States Army does not plan to purchase the IAR.[2][3][4]



In 1985, the U.S. Marine Corps adopted the M249 Squad Automatic Weapon, one year after the U.S. Army. Procurement was a service-level decision because the weapon was adopted by the Army with a contract method the Marines could use. While the belt-fed M249 was portable and had a high volume of fire, it was heavy for its role and unreliable. Gunners could not keep pace with riflemen and the cumbersome light machine gun was not suited for Military Operations on Urban Terrain.[5]


In 1999, a universal need statement was issued for an Infantry Automatic Rifle (IAR). Around 2000, the 1st Marine Division’s 2nd Battalion, 7th Marines Regiment conducted initial limited IAR trials which showed the desire for a light automatic rifle. Experiences in Iraq and Afghanistan continued requests for formal recommendations. The universal need statement spent six years going through the procurement process when it was given official program status in early 2005 and capabilities were drawn up.[5]

The Infantry Automatic Rifle program began on 14 July 2005, when the Marine Corps sought information from manufacturers. Objectives sought by the weapon included: portability and maneuverability; reduction of visual identification of an automatic weapon to the enemy; strengthen the gunner's participation in counter-insurgency situations; and to maintain a high volume of fire. An initial requirement for a 100-round capacity magazine at minimum was dropped in favor of the 30-round STANAG magazine because at the start of testing, available 100-round magazines were unreliable. It had to be 5.56×45mm caliber with non-linked ammunition to be achieve commonality with service rifles.[5][6]

In 2006, contracts were issued for sample weapons to Fabrique Nationale d'Herstal (providing an IAR variant of the FN SCAR), Heckler & Koch (with a variant of the HK416), and Colt Defense, which provided two competing designs. Companies that attempted to compete but were not accepted as finalists for testing include Land Warfare Resources Corporation, which competed with the M6A4 IAR,[7][8] Patriot Ordnance Factory,[3] and General Dynamics Armament and Technical Products with the CIS Ultimax 100 MK5 (marketed as the GDATP IAR).[9]

In December 2009, the Heckler & Koch model beat out the other three finalists, and entered the final five months of testing.[10][11] It was designated as the M27 in the summer of 2010,[12] coincidentally sharing a designation with the M27 link it would not use, but instead it was named after 2nd Battalion, 7th Marines, who were testing with automatic rifles since before September 11, 2001.[13]

An M27 IAR displayed at the NDIA Joint Armaments Conference in May 2010.

While Marine Corps Systems Command was optimistic about operational testing, former Commandant of the Marine Corps General James T. Conway remained skeptical that the reduced firepower at the fireteam-level was a viable option.[14] He felt that while less accurate, the M249 was a belt-fed LMG, which an automatic rifle was unlikely to provide fire superiority over. A magazine-fed rifle would have to reload more often and not be able to sustain firing. Squad members that carry additional magazines for the gunner may be in a position unable to supply the IAR during a firefight. Also, the SAW had been battle-proven and the Army was not pursuing the IAR concept.[5]

After the Marine Corps Operational Test and Evaluation Activity supervised a round of testing at MCAGCC Twentynine Palms, Fort McCoy, and Camp Shelby (for dust, cold-weather, and hot-weather conditions, respectively), limited fielding began for 458 IARs to four infantry battalions (one per each Marine Expeditionary Force and one reserve) and one light armored reconnaissance battalion; all of which deployed to Afghanistan in 2011.[15][16]

In May 2011, General James Amos of the U.S. Marine Corps approved the termination of a Limited User Evaluation (LUE), and the replacement of the M249 LMG by the M27. Fielding of the approximately 6,500 M27 units is expected to be completed in the summer of 2013, for a cost of $13 million. M27 gunners will be equipped with around 22 of the 30-round magazines already in use with the M16 and M4 Carbine. Twenty-two magazines will approximate the prescribed individual combat load of a M249 SAW gunner, and although the M27 gunner is not expected to carry all 22 magazines, they are provided to the units so that a determination can be made at the unit level on what the individual combat load should look like. It will undoubtedly vary by unit, based on the evaluations conducted by the four infantry battalion and one light armored reconnaissance battalion that were issued quantities of the M27 for the LUE. Though program officials are aware that switching from the belt-fed M249 will result in a loss of suppressive fire capabilities, Charles Clark III, of the Marine Corps' Combat Development and Integration office cites the substantially increased accuracy of the M27 as a significant factor in replacing the M249.[17]

Suppressive fire

A U.S. Marine practices firing an M27 IAR on fully automatic fire in April 2012.

The notion that the M27 represents a reduction in suppressive fire has spawned considerable debate among proponents of the M249 SAW within the infantry, and those who advocate that a lighter, more maneuverable, and accurate weapon is sufficient to support offensive operations at the squad level. It is debatable, in fact, that program officials actually concede a loss of suppressive fire capabilities, as the only statements of concern over this concept were made by General Conway.

Beyond the increased accuracy another proposed benefit of the M27 over the M249 are that it is in many respects a modified M4 rifle as used by the rest of the squad. This makes it far more suitable for operating indoors and in other cramped situations where its reduced size and weight make it faster and easier to handle. Although not ideal for close quarters fighting, it is far better in this function than the M249.

With a SAW, the doctrine of fire suppression was the sound of continuous fire with rounds landing close to the enemy. While the M249's volume of fire may be greater, it is more inaccurate. Experienced troops who have dealt with incoming fire are less likely to take cover from incoming rounds if they are not close enough. With an IAR, the doctrine is less volume of fire is needed with better accuracy. Less rounds need to be used and automatic riflemen can remain in combat longer and in more situations.[5]

Combat reviews

1st Battalion 3rd Marines was deployed to Afghanistan in April 2011 with 84 IARs. Former SAW gunners initially did not like the M27, but appreciated it as time went on. It weighed 9 lb loaded, compared to 22 lb for an M249, which was a significant difference when on 5-hour long missions. Gunners said it was "two weapons in one," being able to fire single shots accurately out to 800 meters and have fully automatic fire. It also blended in with standard M16-style service rifles, so the enemy did not know who was a machine gunner. The battalion leadership also saw the M27 as better at preventing collateral damage, as it is more controllable on automatic than the M249. Concern of volume of fire loss was made up for through training courses developed in December 2010. With the M249 SAW, the idea of suppression was volume of fire and the sound of the machine gun. With the M27 IAR, the idea of suppression shifts to engaging with precision fire, as it has rifle accuracy at long range and automatic fire at short range. Shooters transitioned from long-range precision fire at 700 meters to short-to-medium suppressive fire at 200 meters, both while in the prone position. Some gunners in combat have been used as designated marksman. An M27 gunner with one aimed shot has the effect of three or four automatic shots from the SAW, and still has the option of a heavier volume with an accurate grouping.[18]

Marines issued with the M27 enjoy its familiarity with the M4-style weapons in service. It is more friendly to troops due to its cleaner, lightweight system having fewer moving parts and jams. IAR gunners consider the rifle-grade accuracy to be a huge improvement over the SAW, despite the loss of sustained firing. With a shrinking budget, the Marine Corps is looking at ways to implement the IAR as a multipurpose weapon. Suggestions include use as an automatic rifle and as a designated marksman rifle.[19]


Close up view of a U.S. Marine armed with an M27 IAR affixed with ACOG Squad Day Optic.

The M27 is based on the Heckler & Koch HK416, which in turn derives from the M4 carbine and Heckler & Koch G36.[20] It features a gas-operated short-stroke piston action with a rotating bolt. The free-floating barrel is surrounded by MIL-STD-1913 Picatinny rails for use with accessories and optics. The simpler gas-piston rifle system reduces the amount of time it takes to resolve malfunctions on the IAR compared with the M249.[13] The M27 is so similar to the standard M16A4 that its bolt carrier can fit into one and chamber a round. Conversely, an M16 bolt carrier cannot fit into an M27.[1] Alternate calibers other than 5.56 mm are being considered for the M27.[5]


The IAR will be distributed one per four-man fireteam, three per squad, 28 per company, 84 per infantry battalion, and 72 per Light Armored Reconnaissance Battalion,[21] with 4,476 total for the Marine Corps. Nine M249s will still be available per company in reserve.[13][18]


The M27 draws ammunition from a standard 30 round STANAG magazine. Due to its role, high capacity magazines of between 50 and 100 rounds are being explored.[13] The M27 has been successfully test fired with the Armatac SAW-MAG 150 round drum magazine.[22] The improved STANAG magazine with the tan-colored anti-tilt follower is favored over the previous version with the green follower because it can be inserted more easily and the anti-tilt follower can handle high rates of automatic fire with less chance of malfunction. While a rifleman normally carries seven 30-round magazines, an IAR gunner has to carry up to 16, and may carry as many as 21, due to its role and automatic rate of fire. The magazine well has a flared opening that aids in magazine insertion, but cannot be inserted with a PMAG 30 GEN M2 magazine due to the frontal plastic bevel on the PMAG.[1] Because the M27 cannot be fed from the widely used M2 PMAG magazines that M4s or M16 rifles in the squad could take, the Marines banned the polymer PMAG for issue on November 26, 2012 to prevent interchangeability issues.[23] In response, Magpul began the process of arranging verification and official testing for their newer PMAG 30 GEN M3 magazine, which is compatible with both the M27 and M16-series rifles.[24]


The M27 is essentially an HK416 D16.5RS with accessories required by the Marine Corps.[25] The standard optic is the Trijicon ACOG Squad Day Optic (SDO), officially designated the Sight Unit, SU-258/PVQ Squad Day Optic. It is a 3.5×35 machine gun optic that has a Ruggedized Miniature Reflex (RMR) sight screwed on top for close-quarters engagements under 100 meters. Created for the SAW, the day optic offers more magnification and longer eye relief than the ACOG Rifle Combat Optic (RCO) on M16s and M4s. The longer relief helps reduce injury risk from recoil.[1][18] It is issued with the Vickers Combat Applications sling and rail sling mounts, AIM Manta Rail Covers, Harris bipod, KAC backup iron sights, a foregrip, and bayonet lug.[26] The M27 initially had a Grip Pod, which is a foregrip with bipod legs inside, but it was later replaced by a separate foregrip and bipod.[5]

See also


  1. 1.0 1.1 1.2 1.3 1.4 M27 First Impressions -, 20 April 2013
  2. Lamothe, Dan (February 4, 2009). "Marines to test, evaluate 4 auto-rifle models". Marine Corps Times. Retrieved 2 July 2010. 
  3. 3.0 3.1 Cox, Matthew (September 15, 2008). "So long, SAW?". Marine Corps Times. Retrieved 2 July 2010. 
  4. "Corps to Replace SAW With Automatic Rifle". 2011. Retrieved 20 July 2011. 
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 From BAR to IAR – How the Marines Finally Got Their Infantry Automatic Rifle -, 20 November 2012
  6. "10—Non-developmental, 5.56mm, Infantry Automatic Rifle (IAR)". FedBizOpp. July 14, 2005. Retrieved 20 August 2010. 
  7. "M6A4". LWRC. 2009. Retrieved 2 July 2010. 
  8. "Opening Round". Retrieved 3 February 2011. 
  9. Crane, David (October 21, 2008). "GDATP IAR (Infantry Automatic Rifle)/Ultimax 100 MK5 LMG/SAW (Photos!)". Defense Review. Retrieved 2 July 2010. 
  10. Lamothe, Dan (December 4, 2009). "H&K is frontrunner in IAR competition". Marine Corps Times. Retrieved 16 December 2009. 
  11. Lamothe, Dan (December 3, 2009). "Corps chooses H&K to make SAW replacement". Marine Corps Times. Retrieved 20 August 2009. 
  12. Lamothe, Dan (July 2, 2010). "Conway eyes additional testing for auto-rifle". Marine Corps Times. Retrieved 2 July 2010. 
  13. 13.0 13.1 13.2 13.3 Marines swap firepower for accuracy with IAR -, June 29, 2011
  14. Lamothe, Dan (April 19, 2010). "Corps may field infantry auto-rifle this fall". Marine Corps Times. Retrieved 19 April 2010. 
  15. Lamothe, Dan (August 9, 2010). "SAW replacement set for real world testing". Marine Corps Times. Retrieved 10 August 2010. 
  16. "Infantry Automatic Rifle: Update on a Marine Corps Priority Weapon System". MCOTEA Journal. United States Marine Corps. August 2009. p. 9. Retrieved 27 October 2010. 
  17. "Corps to Replace SAW With Automatic Rifle". 2011. Retrieved 16 July 2011. 
  18. 18.0 18.1 18.2 IAR wins over skeptical Marine infantrymen -, 19 July 2011
  19. M249 Light Machine Gun: Endangered species for Marines in Afghanistan -, November 12, 2012
  20. Crane, David (December 4, 2009). "U.S. Marine Corps Selects Heckler & Koch Infantry Automatic Rifle (HK IAR) Candidate as Replacement for FN M249 SAW/LMG". Retrieved 20 August 2010. 
  21. M27 IAR -, May 16, 2012
  22. Armatac SAW-MAG for USMC’s HK M27 IAR -, June 8, 2010
  23. Marine Corps bans popular rifle magazines -, November 26, 2012
  24. Magpul speaks out on the Marine Corps polymer magazine ban - Militarytimes, November 30, 2012
  25. Breakdown: M27 IAR vs. HK416 -, October 24, 2011
  26. The U.S. Marine Corps’ New M27 IAR -, September 10, 2012

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