Marine Corps IAR M27

(By guest author Sam Bocetta)

The US Marines are soon to receive a new weapon, the M27 Infantry Automatic Rifle (IAR). Designed to replace the M249 light machine gun, this new rifle is something of a technological marvel.

Chambered in the 5.56mm round also used by the M4A1, the new rifle is designed to improve the manoeuvrability of US Marine infantry troops, and is based on the Heckler and Koch HK416. The HK416 has seen increasing use in recent years, having been recently designated as the official weapon of the French Army, and its standardization as the M27 promises to improve the combat effectiveness of US troops.

Currently, the US Marine Corps plan to purchase 6,500 of the new rifle. Though nominally used as a replacement for the M249 light machine gun, approximately 8,000 – 10,000 M249s will be retained in active service. The idea is to give company commanders another option on the battlefield.

At present, the new rifle is to be used solely by the US Marines. Though there have been recent calls for the US Army to also replace its standard rifle, at present it has no plans to purchase the M27.

The M27 offers several advantages over the M249, and makes use of the latest technology. Let’s take a look at the history, and some of the features, of this new weapon.


  • History


The M249 machine gun that the M27 replaces it itself a good weapon, though definitely showing signs of its age. Initially purchased in 1985 in a joint decision with the US Army, the belt-fed M249 is quite portable, and offers a high volume of fire. However, it is also pretty heavy, and by 1999 it was realized that a lighter weapon was required for urban conflicts.

Specifically, it was felt that an infantry automatic rifle (IAR) was required to improve combat effectiveness in Iraq and Afghanistan. A program to purchase such a weapon was put in place in 2005, when the desired characteristics of a new weapon were sent to arms manufacturers.

The requirements for the new weapon were quite stringent. It had to be portable and reliable, and also look similar to other weapons in the squad so that the gunner would not attract undue attention from the enemy. It had to be suitable for counter-insurgency operations, and be capable of maintaining a high rate of fire. The new rifle had to be chambered in the 5.56mm round, to ensure compatibility with other weapons in the squad.

Several manufacturers submitted designs to be evaluated, including both Heckler and Koch and Colt. Ultimately, it was the HK 416 that won the competition, and in December 2009 this weapon began a five month period of testing.

Though some in the Marines were initially sceptical that a magazine-fed 5.56mm rifle would not be able to maintain the same rate of fire at the belt-fed M249, in the end the enhanced portability of the HK416 won it many converts. Though undoubtedly delivering less firepower, it is also a more accurate weapon than the M249, and the reduction in importance of suppressive fire means that this is now a more pressing concern than in years past.


  • Design


One of the most striking features of the M27, and one of it’s advantages over standard infantry rifles, is that it is a “gas-piston” rifle. In M16, which are still used by most of the US armed forces, the hot gases generated by each round are vented inside the weapon. This can eventually lead to corrosion, reducing the reliability of these weapons. In contrast, the M27 uses these gases to drive a piston which advances the gun’s mechanism, and then vents this gas outside the weapon. This means that the weapon is more reliable, and also easier to maintain in the field.

The M27 also features four rails for mounting optics, and a wide variety of accessories are used by troops in the field. Though alternative calibers are being considered, at the moment the M27 comes chambered only for the 5.56mm round.

The standard magazine for the M27 is a 30-round STANAG unit. However, larger magazines are being considered, and the weapon has been successfully tested with a 150-round drum magazine. One reason why the M27 uses the relatively small 5.56mm round is that this allows more magazines to be carried, which is especially important for automatic weapons – while the average rifleman normally carries seven magazines, the IAR gunner must carry up to 16, and sometimes as many as 21.

Many accessories have been added to the M27 by the Marine Corps. The original HK416 was a very adaptable gun, and has been extensively modified by both civilian and military users. Like the AR-15 lower reciever, the M27’s receiver can be used as a base on which to fit various barrels and other parts. The standard optic issued to Marines with the M27 is the Trijicon ACOG Squad Day Unit, a 3.5×35 machine gun optic which offers slightly less magnification but longer eye relief than the standard optic on the M16, in order to facilitate close-quarters combat.

One interesting development, and an unusual one for an automatic weapon, is that the M27 has been trialed with a suppressor mounted. For a while now, the US Marines have been considering suppressing every weapon within a squad, because tests suggest that this improves communication and combat effectiveness. Though suppressors generally increase the weight of a weapon, and complicate the maintenance of them, these tests continue.


  • In The Field


Initial field assessments of the M27 have been positive. In combat, the weapon is distributed to one man in a four-man fireteam. Gunners have reported that the light weight of the weapon, in comparison to the M249, makes it much better for extended missions. In addition, the M27 has been called “two weapons in one” – able to deliver accurate single shots out to 800 metres, but also devastatingly effective at short range on automatic fire.

It remains to be seen, of course, whether the M27 will achieve the cult status of other military rifles like the M16 or the AR-10. However, at first glance this looks like a powerful, portable, and reliable weapon.

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