The weapon that future U.S. warfighters will be carrying into action is still yet to be determined, but a final option could be selected soon. This month the U.S. Army picked three finalists to replace its legacy M4 carbine and M249 squad automatic weapons. Each of the weapons has starkly different designs, but notably each will be chambered for the new 6.8mm round, which was developed to be more lethal than the currently used 5.56mm NATO ammunition.

Replacing both the M4 and the M249 has presented no small challenge – notably because of how different each weapon is, and how these have been deployed.

The M249 light machine gun (LMG), formerly designated as the M249 Squad Automatic Weapon (SAW), has been in service since 1984 and was introduced to provide automatic firepower to small units. It offers the high rate of fire of a machine gun combined with the accuracy and portability of a rifle. It is an American adaptation of the Belgian FN Minimi, and it features a gas-operated long-stroke pistol, open bolt action. It has a muzzle velocity of 915 m/s and an effective firing range of 700 meters.

The M4 Carbine, which is in essence a shorter and lighter variant of the long-storied M16A2 assault rifle, has been in service since 1994. It can be used with M203 and M320 grenade launchers and offers semi-automatic and three-round burst firing modes, while the M4A1 variant offers semi-automatic and fully automatic firing modes.

The United States Marine Corps is already opting to replace the M249 with the M27 Infantry Automatic Rifle (IAR), chambered in the 5.56mm NATO round. However, the Army has opted to replace both the M4 and M249 with a single weapon.

Three Different Options

Last August the service awarded transaction authority agreements to Sig Sauer, General Dynamics Ordnance and Tactical Systems and Textron Systems. All three companies will provide prototypes for soldier evaluation by the end of the year.

The Sig Sauer design is actually two versions, each reportedly based off its MCX firearms line. It features a folding stock capability along with a machine gun version with 16-inch barrel and a rifle version with 13-inch barrel. The overall design of Sig Sauer’s firearm is similar enough to the legacy systems that soldiers shouldn’t need additional training.

General Dynamics has opted for a more “radical” approach with a bullpup design, which is when the firearm’s magazine is placed behind the pistol grip. This reduces the overall length of the weapon as the magazine is essentially in the stock, but allows for a full-length barrel. In fact, bullpups can offer longer barrels, which can improve accuracy, yet be shorter weapons overall. The General Dynamics option has a 20-inch barrel, just two inches less than the M249.

The placement of the magazine could require some additional training, but new soldiers won’t have a frame of reference to compare it to, and by some accounts changing a magazine can be accomplished faster with a bullpup design. The British Army has used the SA80/L85 Rifle, with a bullpup configuration, since 1985, and it was used in the Persian Gulf War as well as in the War in Afghanistan and the Iraq War.

The Textron Systems version is notable in that it isn’t just the firearm that is being completely redesigned from the ground up, but also the ammunition. While Sig Sauer has developed a more traditional three-piece bass case with stainless steel hard and lock washer for its ammunition, General Dynamics has opted to utilize a magnum cartridge but with a composite case. Textron is taking it a step further with its cased telescope ammunition that reduces the weight by using a plastic polymer to completely surround the projectile.

In addition, unlike the magazine-fed designs from both Sig Sauer and General Dynamics, the Textron System design is belt-fed – a trait that is a holdover from the M249. It will still employ a magazine for the rifle version replacement of the M4, meaning that while there will be two variations these will be distinct to what each replaces.

Very Unique Options

Having three distinct options could play into the U.S. Army’s favor.

First of all, the difference in the three offerings – Sig Sauer, General Dynamics and Textron – “will allow the Army to evaluate different technologies, themselves at different stages of maturity,” said Amael Kotlarski, weapons research analyst at Jane’s.

“This was enabled by the ‘open-endedness’ of the initial tender,” Kotlarski told ClearanceJobs. “If this latest program flounders, then the U.S. Army will at least have a good idea of which technologies to pursue down the line.”

The other consideration is the ammunition, something that hasn’t been updated in 40 years. The 5.56 NATO cartridge family is actually even older as it was derived form – but not identical to – the .223 Remington cartridge designed in the early 1960s. While military ammunition can go unchanged for years, and the Russian 7.62x54mmR has been used since 1891, there are proponents suggesting it is time for an update!

“The biggest ‘revolution’ will be in cartridge casing technology rather than in the firearms themselves, with the exception of the Textron weapons – mechanically quite different to what we know today due to the unique nature of their polymer cased telescoped ammunition,” added Kotlarski.

Big Contract Opportunities

Whichever company is able to hit the bullseye could find itself in a good position as the U.S. Army seeks to replace not one but two weapons in the small arms arsenal.

“While not as lucrative compared to a new jet fighter or aircraft program, an opportunity to completely re-define and re-equip a countries’ small arm inventory only comes around roughly once in a generation, so this competition is a pretty big deal for the three contenders,” said Kotlarski.

“Other than the potential direct sales to the U.S., replacing the M4 and M249 would most likely usher in a new NATO standard caliber, something that has not happened in over 50 years,” Kotlarski told ClearanceJobs. “The last time such a major shakeup of the military small arms market occurred was with the introduction of the M16 and the 5.56 NATO round in the early 1960s. This would open further opportunities for either direct sales or licensed production of weapons and ammunition abroad for decades to come.”

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Peter Suciu is a freelance writer who covers business technology and cyber security. He currently lives in Michigan and can be reached at You can follow him on Twitter: @PeterSuciu.