Several months ago, the Army’s Project Engineering Office for Individual Weapons announced it was looking for sources to pursue what it called M4A1+, a series of upgrades to the M4A1 carbine that will be sourced from commercially existing components.

Lt. Col. Terry Russell, the project manager for Individual Weapons at Picatinny Arsenal, New Jersey related the impetus for the program in an Army Times story: “We’re always trying to modernize and upgrade the weapon to make sure we’ve got the best weapon available … There are no deficiencies that we’re trying to correct; we’re just trying to make sure it remains a premier weapons system.”

Task & Purpose has covered upgrading the M4 with commercial parts before, but Russell’s remarks have clarified the scope and direction of the M4A1+ program; they also indicate changing attitudes regarding carbine gunfighting in the Army.

One of the most significant upgrades would be a new modular railed forend. The Army has specified that the rail be at least 12 inches long. The longer rail would allow soldiers to accommodate the thumb-over-bore shooting technique, which straightens the elbow of the support hand and allows the shooter to better manage recoil. While thumb-over-bore has been around for decades, the technique has entered the shooting mainstream. The Army also wants the rail to be free-floated, eliminating outside forces like sling pressure and the shooter’s grip that affect the barrel’s accuracy. The Army’s acknowledgement of current shooting techniques and technology with the M4A1+ design is welcome sign of evolving thinking regarding the infantry rifle.

Over the past 15 years, accessories like lights, infrared aiming lasers, and foregrips have become a common sight on infantry rifles. This has added weight to the carbine, while also crowding the limited space on the current issue seven-inch long Knight’s Armament rail. The Army has therefore asked that the new rail feature a continuous length of Picatinny rail in the “12-o’clock” position, with modular rail segments of varying lengths for the other sides of the rail. This saves weight, slims the profile of the handguard, and allows the user to mount only the rail space he needs.

There are plenty of products on the market that fit this description; including the Knight’s Armament URX, Geissele Automatics Super Modular Rail and the Centurion Modular Rail. It’s understandable why the Army would retain the Picatinny rail standard; virtually all the accessories it issues to troops use it. But the Army could plan ahead by adopting one of two new attachment standards. Finally, the Army wants the rail to be a more neutral coyote tan color, in order to disrupt the outline of the carbine and impede visual detection.

The first is an open-source system called Keymod, which features a key-shaped chamfered slot and nut system. Introduced in 2012, the open-source nature of the system has ensured that many railed forends and accessories are now on the market. M-LOK, developed by well-known gun accessories company Magpul Industries, uses a T-nut and lug system. The system is licensed freely by Magpul in order to maintain manufacturing standards. M-LOK is fairly new, so there are less rail and accessory options available. Both Keymod and M-LOK allow accessories to be directly mounted, saving weight, and allowing for a tighter overall profile that aids in weapons manipulation. Both systems also feature legacy Picatinny rail adapters, so the Army could adopt either one, and replace accessories with the appropriate direct-mounted version as time goes on.

The M4A1+ solicitation provides a goal for improved accuracy: “The system accuracy for the M4A1+ shall be 5 inches mean radius at 300 meters throughout barrel life (required) and shall be 5 inches extreme spread at 300 meters throughout barrel life with .9 probability (desired) and shall be 10 inches extreme spread at 600 meters throughout barrel life with.9 probability (desired).”

This is actually a pretty ambitious accuracy goal, considering the M4A1+ program does not alter the stock barrel. Free-floating rails will enhance the accuracy of the M4A1, but the barrel and ammo will also contribute heavily. As such, the Army has label this specification as “desirable,” rather than required.

The extended rail means that a new low-profile gas block is required, along with the option of removable front and real sights. The increasing prevalence of optics on infantry rifles means that more traditional iron sights are less important. Removing them shaves off a little more weight from the weapon. Still, the Army plans to purchase flip-up irons sights as part of M4A1+, for those without optics or who desire a backup sight to their primary optic. Dozens of companies produce these parts; so the Army will be spoilt for choice.

A new flash suppressor has also been requested, with the goal being “to reduce the day and night firing signature and night vision device blooming effect of the weapon to be less than the current carbine without loss in system performance.” The only other requirement is that it be compatible with is a blank-firing adapter for training purposes. It seems the Army opted to forgo the option of brakes and other hybrid muzzle devices, likely due to concerns about hot gas and debris from muzzle blasts hitting those adjacent to the shooter in range and close-quarters combat settings. Surefire, Advanced Armament Corporation, and B.E. Meyers have all provided flash hiders to special operations units in the past; they’re also popular on civilian AR-15s.

Perhaps the most surprising request is for an internal change to the M4A1. The Army wants to outfit M4A1 being used as designated-marksman rifles with precision triggers that feature less trigger pressure and travel. Russell explains the advantages of such a trigger: “It’s very sensitive to the touch. When pulling the trigger you don’t have to pull it as hard, which allows you to maintain accuracy on the target … At shorter distances it (the difference in accuracy) is not that significant, but at longer range, it becomes more significant.” Aftermarket triggers like this are becoming popular in civilian shooting circles; Geissele Automatics and ALG Defense are well-known options.

There are several other requests, like quick-detach sling mounts and ambidextrous charging handles. The Army also has its Soldier Enhancement Program, which is looking to field improvements like better cleaning equipment and zeroing tools. Some other commercial upgrades the Army might want to pursue include better accessory switches and more ergonomic pistol grips. One note of concern is that the Army wants to source all these upgrades save the trigger from the same vendor. This could potentially limit the options the Army has for upgrades, and prevent the best possible parts from getting selected. But the fact that the Army is pursuing these upgrades at all is a welcome indication that the M4A1 carbine will be brought up to the latest standards as a modern weapon system.