SOCOM’s latest rifles embrace the 6.5 Creedmoor cartridge

While the big Army is obsessed with the new 6.8x51mm round, SOCOM is looking at a commercial off-the-shelf option in the form of the 6.5 Creedmoor.

Over the last couple of years, SOCOM has adopted two new carbines chambered in the 6.5 Creedmoor cartridge: the MRGG-S and the MRGG-A.

The 6.5 Creedmoor is a full-power rifle round designed by Hornady and Creedmoor Sports for the commercial market. The cartridge’s initial purpose was to provide a long-range target round that could fit into short-action weapons. This allowed the 6.5 Creedmoor to function effectively in the same types of rifles that fire 7.62x51mm cartridges.

On the commercial market, the cartridge became an instant success. It’s incredibly challenging for new cartridges to gain traction in the modern marketplace. For a new cartridge to succeed, it has to offer substantial benefits over other cartridges in its category. The 6.5 Creedmoor did just that: It provided excellent ballistics, amazing accuracy, and a considerable increase in range without having to increase the overall size of a rifle platform.

After the cartridge proved successful in the commercial market, the military took notice.

Special operators tend to have a little more leeway in their caliber selection and use and the 6.5 Creedmoor would be an adequate replacement for the 7.62x51mm cartridge in the armories of special operators.

SOCOM found that when using rifles chambered in 6.5 Creedmoor, soldiers had twice the likelihood of hitting targets at 1,000 meters, or 1,093 yards. So, SOCOM went shopping for two new guns, the MRGG-S, which stands for Medium Range Gas Gun – Sniper, and MRGG-A which stands for Medium Range Gas Gun – Assaulter.

The Medium Range Gas Gun – Sniper

The MRGG-S rifle. (Geissele Automatics)

SOCOM chose Geissele Automatics for the MRGG-S project in 2023. Although “sniper” is in the rifle’s name, according to SOCOM, the rifle will be used in a designated marksman or sniper support role. The MRGG-S has all the modern features you expect from a sniper rifle. Its 20-inch barrel is free-floated meaning that nothing touches it, which could affect the rifle’s accuracy.

The MRGG-S features a cold-hammer-forged, matched barrel designed to maximize accuracy and stability out to extreme ranges. The rifle uses a two-stage match-grade trigger system to help eliminate some of that human error and deliver a smooth trigger pull that’s consistent and predictable.

The rifle is semi-automatic and is based on the Stoner design used for the M4 and AR-15, just upscaled to fire the more powerful, full-sized rifle round. Prior to the M16, Stoner had created the AR-10, which was a full-powered rifle firing the 7.62x51mm. For all intents and purposes, the MRGG-S and the MRGG-A are AR-10 type rifles. The semi-auto action offers faster follow-up shots and allows troops to repeatedly engage or even suppress the enemy if necessary.

The MRGG-S features a fixed stock with an adjustable comb for use with optics. The optic of choice is unknown, but I’d imagine it will be used with Nightforce optics since they seem to be a SOCOM favorite. Overall, the MRGG-S is a modern, fairly lightweight, and compact platform that’s extremely precise and capable.

Related: Is the Army’s new M7 rifle a step back over its predecessor?

The Medium Range Gas Gun – Assaulter

The MARS-H 6.5 DMR rifle. (LMT Defense)

The MRGG-A, or Medium Range Gas Gun – Assaulter, is a similar platform to the sniper variant, but overall more compact. With a 14.5-inch barrel, it falls into the size range of the M4 carbine, albeit it has a heavier profile. As the name suggests, MRGG-A is designed for assaults, room-clearing, and general combat duty.

For the MRGG-A platform, SOCOM chose the LMT MARS-H series that stands for Modular Ambidextrous Rifle System-Heavy. As the name implies, the rifle is fully ambidextrous.

Its carbine-like size makes it much more maneuverable than the sniper variant. The weapon can be used well inside and outside of vehicles, as well as in close-quarters combat.

One of the most interesting features of the MARS-H series rifles is its monolithic upper receiver: The rail and upper receiver are all one single piece which gives users increased rigidity and allows them to mount various optics and laser-aiming devices from front to rear.

While this smaller carbine variant won’t offer the same range as the sniper model, it will offer more range than the standard M4 carbine as well as more terminal ballistic performance on target. The assaulter version gives troops in open areas an edge on standard assault rifles. If you can hit your enemy at ranges they can’t even engage you at, then you have a remarkable edge.

The Creedmoor will continue to see success in and out of SOCOM. The command seems dedicated to the cartridge and has proposed a variety of rifles and even machine guns chambering the round. The Creedmoor’s increased range and accuracy over the 7.62x51mm makes it tough to ignore and since it is already available, there isn’t a costly selection process necessary to develop a new cartridge. The Creedmoor does a lot of things right and will likely be SOCOM’s preferred cartridge for the near future.

Feature Image: U.S. Army Green Berets with 10th Special Forces Group (Airborne) kneel in position while preparing for their next movement during a joint training exercise at Fort Carson, Colorado, Aug. 13, 2025. (U.S. Army photo by Sgt. Rhianna Ballenger)

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