The Marines' M27 LMG Substitute: Hit, or Miss?

The US Marines are about to try an experiment that would change the way their squads fight. Its test will take place in Afghanistan, starting this fall. The good news is that front lines reviews will be the key, not back-room maneuvering. The bad news is that the test may miss the boat on the real battlefield evolution taking place in Afghanistan, which aims to reclaim the traditional infantry half-kilometer.

What’s beyond question is that many of the Corps’ existing 5.56mm M249 Squad Automatic Weapon (SAW) light machine guns are getting old, reporting problems, and need replacement. The question was, with what?

A 2005 solicitation asked for a gun that was at least 30% lighter than the 15-17 pound SAW, could fire from the open or closed bolt position to give it single-shot and “first through the door” capabilities with less “cook off” risk, and used switchable 30-round magazines instead of a belt feed. Basically, they wanted an assault rifle that could stand up to higher firing rates, offer better accuracy than an LMG, and be more useful in the close-quarters urban combat that had dominated Iraq.

They got what they wanted. The December 2008 short list of contracts to Colt, FN-USA, and HK didn’t include General Dynamics’ Ultimax 100 Mk5 LMG; and in October 2009, a variant of the reliable HK416 assault rifle in use by American special forces won the shoot-off. The HK416 replaces the M4 carbine’s upper receiver with a short-stroke piston system that soundly beat the standard M4/M16 in May 2007 US Army reliability tests.

But will the new “M27 IAR” work in combat, in this role? USMC Commandant Gen. Conway isn’t fully convinced. From a December 2009 press conference:

“Let’s step away from accuracy for a moment and talk about suppression, and the psychology of a small-unit fight, that says if other guy’s got a light machine gun and I’ve got an automatic rifle, I’m going to be hard-pressed… to keep his head down instead of him keeping mine down…. let’s talk about what it does to squad tactics…. every 30 rounds, you gotta change magazines…. [the problem is that] fire superiority is fleeting…. I’m concerned that moving at night… the other squad members carrying those additional magazine for that automatic rifleman, might in a spread formation be hard pressed to get him what he needs in a timely fashion…. I don’t want to get so far in the weeds… but it’s a big deal when you start changing how a Marine infantry squad fights, and, and, we’re gonna treat it as a big deal…”

Those are absolutely the right questions. Psychology matters. The vast majority of units break morale or become ineffective long before they’re wiped out, and keeping the enemy’s head down saves lives.

In response, however, some will point to the Marines’ own 2008, fight at Shewan, Afghanistan. The Taliban put 250 jihadis up against 30 Marines in an ambush. They lost 50 or so jihadis, in exchange for one wounded Marine. Marine marksmanship was key, and was cited as an important reason the enemy couldn’t get its act together. One USMC designated marksman racked up 20 kills – in 20 shots. Oorah!

So, cyclic LMG suppression, or 65 shot per minute accuracy with smaller magazines, and no quick change barrel?

What if that’s the wrong question?

Despite terrible Taliban marksmanship, the central problem of Afghanistan for many Western armies is very different from Iraq. Iraq was all about close quarters battle in the urban fight. Afghanistan is serving as a reminder that marksmanship and range still matter; Shewan aside, many engagements are taking place against enemies more than 300 yards away. At those ranges, light 5.56mm rounds lose accuracy and killing power. Hence seminal papers like Major Thomas P. Ehrhart of the Command and General Staff College’s “Increasing Small Arms Lethality in Afghanistan: Taking Back the Infantry Half-Kilometer.” Hence US Army moves to add 7.62mm M14s to their infantry squads, and replace some 5.56mm M249 SAWs with the 7.62mm M240 GPMG, including the new part-titanium M240L. Hence efforts by the British to supplement their 5.56mm SA80A2 assault rifles with the new 7.62mm L129A1 Sharpshooter rifle, essentially an accurate assault rifle.

Despite repeated studies showing significant benefits from 6.8mm SPC or 6.5mm Grendel as a standard caliber, the US military hasn’t led. As a result, the realities of combat are forcing them to field mixed-caliber squad weapons.

The M27 IAR might be the right idea for the USMC squad, but its 5.56mm caliber bucks a key trend, and may limit its usefulness in the very environment that seems tailor made for its type of weapon. Suppressive fire that relies on accuracy, range, and penetrating power through obstacles, while still being useful in close quarters battle, can make a big difference to the 13-man Marine squad in environments like Afghanistan. It would be equally useful in the “MOUT” urban warfare that’s expected to make up a large share of future fights.

Unfortunately, that isn’t what the Marines are getting. The 7.62mm HK417 is very similar to the base 5.56mm HK416 design that won, but a caliber shift would likely force a do-over for the entire competition. If its little brother the M27 IAR fails to measure up, the response will likely be a drift back toward a 5.56mm light machine gun. And the branch of the American military best positioned to exploit a 7.62mm suppression and assault weapon, could end up being an anomaly because they don’t have one.