Key point: The M27 might not be as good as thought and is also expensive.

For over a half century, the M16 assault rifle—and later the more compact M4 carbine—have served as the primary service rifles for both the U.S. Army and Marine Corps. The “plastic toy rifles” have evolved considerably since their troubled debut in Vietnam, and boast greater ranged accuracy (but also greater maintenance requirements) than Kalashnikov rifles they have often faced in battle.

Nonetheless, both the Army and Marine Corps are finally looking for a replacement—and the latter service has selected the heavier M27 Infantry Automatic Rifle and has plans to eventually requisition as many as fifty thousand. However, cost concerns and recent performance evaluations have raised doubts about the plan and Congress recently delayed funding the transition.

The M27 is a variant of the German Hechler & Koch HK416 assault rifle, which has already long served with U.S. Special Forces—one was used in the killing of Bin Laden—and more recently been inducted as the service rifle of the French Army. The rifle’s numerical designation comes from its initial testing with the 2nd Battalion of the 7th Marine Regiment way back in 2001.

The HK416 and M27 trace their lineage to the M16 and use the same 5.56-millimeter ammunition and thirty-round magazines. However, in place of the M16’s gas-operated direct-impingement system, the HK416 family uses a heavier short-stoke piston which is cleaner and thus less maintenance intensive. The M27 also comes with a built-in 3.5x magnification ACOG optical sight and a bipod, as well as picatinny rails to add on extra devices.

The Marines first introduced the M27 in 2011 to replace their M249 light machineguns (derived from the Belgian FN Minimi), itself a controversial change. The Corps liked the M27’s dramatically lighter weight (9.8 pounds loaded compared to twenty-two for the M249) and the fact that it looked so similar enough to the M16 that the gunners weren’t liable to be singled-out by enemy snipers. Unlike the Army, Marine doctrine is oriented around aggressive employment of rifle squads, so mobility is greatly valued.

However, while capable of automatic fire, the M27 could only accept thirty-round magazines compared to the M249’s two-hundred-round belts and replaceable barrel. This makes the M27 less suitable for delivering sustained suppressive fire by spraying an area with such a hail of lead the enemy is compelled to keep their heads down rather than shoot back.

But the most touted advantage of the M27 was superior long-range accuracy: in a test, the M27 could consistently land a bullet within a foot of a target at six hundred meters, while the M249 could was only that accurate at one hundred meters. The M27’s proponents argued it would land more rounds on or near target with fewer bullets than an M249—and have a lower likelihood of collateral damage. Currently, each Marine twelve-man rifle squad is equipped with three M27s divided between its three fireteams, while six M249s are retained as company level fire support weapons.

However, the Marine Corps next decided the M27 should replace its standard M16 assault rifles and M4 carbines. Because the M27 was already in service, the Corps could bypass having a time-consuming competition.

The M27’s heavier, thicker barrel allows it to fire up to thirty-six rounds per minute without overheating, whereas an M16 will begin to overheat if sustaining more than twelve to fifteen rounds per minute. There are some tradeoffs, though: the M27 is more than two pounds heavier than an M16, and lacks the handiness of the M4 carbine in close quarters, which can have its stock folded down to thirty inches. The M27 also doesn’t appear to support an M203 under-barrel grenade launcher, so Marine grenadiers must carry both an M27 and a separate M320 grenade-launcher.

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In September 2018, the Marine will phase in a special sniper-variant called the M38 Designated Marksmen’s Rifle, equipped with a variable-power scope (2.5x to 8x magnification). Experience in Afghanistan and Iraq had shown that every squad could benefit from having its own ‘street-level’ sharpshooter to provide precision-fire support to infantry squads within six hundred meters.

The Designated Marksmen and their weapons are not expected to perform to the same standards, or use the same tactics, as elite scout-sniper teams that stalk their prey from greater distances. Nonetheless, the M38 has been criticized for lacking more powerful ammunition and using the dated TS-30A2 scope based purportedly on availability rather than suitability (the scope does not even use the same range increments as the rifle’s adjustment knobs).

Another issue affecting both the M27 and M38 regards the Marine Corps new policy of issuing suppressors as standard equipment for riflemen and even support weapons, at an estimated cost of $700,000 per battalion. Though movies infamously exaggerate the sound-dampening properties of suppressors, they still prove effective at disorienting enemies as to the origin point of an attack by dampening sound and muzzle flash. According to Marine officers, the suppressors also help by decreasing the noise level so that NCOs and officers can more effectively communicate with their own soldiers during battle!

However, a recent internal test document leaked on The Firearms Blog in April 2018 revealed that the M27 and M38 demonstrated serious drops in accuracy when using the standard KAC suppressor—increasing the spread by as much as two to five additional inches off target for every one hundred meters, which could increase the point of impact radius by an entire foot or more at six hundred meters. An alternate OSS modular suppressor system did not exhibit the same accuracy loss but was inferior in terms of reliability and ease of maintenance. As the Marine Corps remains intent on standardizing the use of suppressors, this could pose a major shortfall unless addressed.

The M27’s cost has also caused concern. The M27 originally came in at $3,000 each—or even higher for HK416s. This was reduced to $1,300 in a later bath due to economies of scale, but this is still two or three times the cost of a new M4 or M16.

The Marine Corps is inclined to proceed with the transition to the M27 regardless, with eleven thousand currently on order out of an eventual planned fifty thousand. However, Congress has denied 20 percent of the necessary funding in the 2019 Defense Authorization Act until the Corps can describe a long-term strategy for its small arms.

This is related to the Army’s disinterest in adopting the M27, apparently due to concerns that the 5.56-millimeter round may prove ineffective at penetrating modern body armor at medium or long range. This problem would not be especially apparent when combatting poorly equipped insurgents in Afghanistan, but could become relevant in a conflict against the soldiers of a better-funded near-peer state.

Dealing with this problem may entail returning to the heavier 7.62-millimeter cartridge—there already an HK417 automatic rifle chambered for such a round—but the Army seems interested in a weapon using an “intermediate” round of around 6.5 millimeters for its next generation squad automatic weapons. Currently, the Army is holding a competition to replace its own M249s, to begin entering service in the mid-2020s. Whichever squad automatic weapon ends up being adopted, the Army hopes it will lead to an entire family of related weapons including new service rifles.

If a new family of Army small arms is introduced in 2020s, there will be pressure on the Marines adhere to the new standard—and displeasure that so much money was spent procuring an expensive rifle which may not remain long in service. Still, despite potential future problems, most reports from the field suggest the leathernecks are pretty satisfied with their beefy new assault rifles for now.

Sébastien Roblin holds a master’s degree in conflict resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring. This first appeared in August 2018.

Image: Wikimedia.