In December 2017, the Marine Corps announced that it would equip every member of an infantry squad with the M27, supplanting the M4 carbine which would be retained at the platoon leadership positions and above.

The Universal Need Statement spent six years going through the procurement process before an official program was begun and a list of required capabilities was created in early 2005.

[10] The Infantry Automatic Rifle program began on 14 July 2005, when the Marine Corps sent Requests For Information to arms manufacturers.

[18] [19] After the Marine Corps Operational Test and Evaluation Activity conducted further testing at Twentynine Palms, Fort McCoy and Camp Shelby for dust, cold-weather, and hot-weather conditions, respectively, limited fielding of 458 IARs were sent to four infantry battalions, one per each Marine expeditionary force one reserve, and one light armored reconnaissance battalion, all of which deployed to Afghanistan in 2011.

[20][21][22] In May 2011, Marine General James F. Amos approved the conclusion of the Limited User Evaluation (LUE) and ordered the replacement of the M249 LMG by the M27.

Though program officials were aware that switching from the belt-fed M249 would result in a loss of suppressive fire capability, Charles Clark III, of the Marine Corps' Combat Development and Integration Office, cited the substantially increased accuracy of the M27 as a significant factor in the decision to replace the M249.

[23][24] In early 2017, Commandant of the Marine Corps General Robert Neller said he wanted to equip every "0311" rifleman with an M27 IAR.

As of August 2017, officials stated that "riflemen are the top priority", but that the M27 "will be in the hands of combat engineers and light armored reconnaissance battalion scouts next.

"The new pre-solicitation notice of 50,184 [M27s]", said Woodburn, "is [meant] to up the production capacity that H&K must be able to meet as the sole-source provider [of the M27], should the Marines decide to order more in the future."

[10] The notion that the M27 represents a reduction in suppressive fire has spawned considerable debate between 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.

[citation needed] It also blended in with standard M16-style service rifles, making it difficult for enemy forces to identify the machine gunner.

[citation needed] Due to budget limitations, the Marine Corps is looking at ways to implement the IAR as a multipurpose weapon.

[35][36] It features a gas-operated short-stroke piston action with a rotating bolt and a cold hammer forged[37] free-floating barrel.

[39] To rectify the incompatibiliy, Magpul developed the PMAG 30 GEN M3 magazine, which is compatible with both the M27 and M16-series rifles and is in the process of arranging verification and official testing.

[40] After Marine Corps testing of the M855A1 Enhanced Performance Round with the M27 showed reliability problems from feeding issues from standard magazines,[41] leading to the introduction of the PMAG 30 GEN M3 Window, which had better reliability with the EPR, was approved for use by Marines in December 2016, so that M27 gunners who receive M855A1 rounds do not face such issues.

[19] Unlike the original HK416, the rifle does not utilize HK designed iron sights, instead using USMC approved accessories.

The SU-281/PVQ is a variable-power magnified day optic that comprises a noncaliber-specific reticle and an illuminated or nonilluminated aim-point and is intended to supplement the attrition and replacement of the older ACOG RCO and SDO sights for weapons including the M27.

In January 2017, a USMC unit deployed with KAC NT4 QDSS suppressors mounted to their M27 rifles as part of a concept to suppress every weapon in an infantry battalion.

Disadvantages included additional heat and weight, increased maintenance, and the greater cost of equipping so many troops with the attachment.

[52]The M38 Squad Designated Marksman rifle (M38 SDMR) is essentially the same as the M27 IAR and retains its selective fire capabilities.

One M38 marksman version, fitted with a scope and QDSS suppressor, is to be fielded per infantry squad to engage targets out to 600 meters.

This article incorporates public domain material from websites or documents of the United States Marine Corps.