The U.S. Army has selected a new round to replace those equipping its M4A1 carbine and M249 Squad Automatic Weapons. The Army selected five companies to produce prototype weapons in the new, mysterious 6.8-millimeter round.

Since the 1960s, the U.S. Army has used the 5.56-millimeter round. The number refers to the diameter of the bullet, which also corresponds to .22 inches. Unlike civilian .22 rounds however the 5.56 round is heavier, longer, and travels at greater velocity, transferring much more energy to the target and causing much more serious wounds.

Advertisement - Continue Reading Below

Recently, the Army decided the 5.56 round was not going to cut it against modern body armor, particularly that worn by Russian Army troops. The service called for a larger, heavier round that could penetrate current and future body armors, but at the time, the service was kind of elusive about what exactly that caliber would be. The new round is also expected to be accurate to greater ranges.

M249 Squad Automatic Weapon. U.S. Army photo by Spc. Rolyn Kropf

Now, we know the answer: The Army is bumping up to 6.8mm, adding more than a millimeter in diameter. This is close to the caliber the Army fielded in the early 1960s, the 7.62x51 round. The older round features considerably greater recoil than 5.56, making it more difficult to deliver rounds accurately in automatic fire. The 6.8 is an attempt to reach a compromise between the two.

In July, the Army awarded contracts to AAI/Textron Systems, FN America, General Dynamics, PCP Tactical, and Sig Sauer. The Next Generation Squad Weapon will replace the M4A1 carbine, while the Next Generation Squad Automatic Rifle will replace the M249 Squad Automatic Weapon. The M4A1 arms individual infantrymen, while one in three soldiers carries the heavier, faster-firing M249 for suppressing enemy fire. Each company will submit one prototype NGSW and one NGSA, but FN is allowed to submit two different variants. The prototypes are due in July.

According to the Prototype Opportunity Notice posted online, the Army wants the new weapons to fire in semi-automatic and fully automatic modes and share the same ammunition magazine. They must include a flash hider for minimizing muzzle blast at night time, a removable sound suppressor, and a carry sling. The weapons must be resistant to rust, scratches, chemical, biological, and nuclear weapons, electromagnetic pulse, and cyber attacks (something for the contractors to keep in mind if the weapon is electrically controlled), and must come in some shade of Coyote, a shade of brown popular with the U.S. military. They must function in “all environments and weather conditions” and come equipped with a so-called “Picatinny rail” for mounting of optics, aiming lasers, and other weapon enhancements.

Advertisement - Continue Reading Below

The 6.8SPC round (left) vs. 5.56 round (right). The Army’s 6.8 round may not have the same characteristics as the round pictured, but it will be the same width. Wikipedia Editor Hellbus Wikimedia Commons

Not much is known about the Army’s new 6.8-millimeter round. A 6.8mm Remington Special Purpose Cartridge, invented in 2002 by U.S. Special Forces, exists but critics charge it exhibits only marginal improvements over 5.56. It could be the round in question, but maybe not. It could be an enhancement of that round, or something different altogether that shares the same width.

Of the five companies, the Army will choose three to produce weapons in 6.8 caliber. Production, according to Army Times, could start as early as 2021 and involve up to 250,000 of both guns over a ten year period. Given that the Army, Army Reserves, and National Guard combined are much larger, a second order would almost certainly follow, for up to a million brand-new weapons.

Fielding a new weapon in 6.8 will put the Army at odds with the Marine Corps and America’s NATO allies when it comes to ammunition. The Pentagon has traditionally tried to standardize on a single or carbine caliber to streamline logistics and enable US and NATO forces to share ammunition. The U.S. Marines are content with their 5.56 weapons to the point where they are planning to standardize the Heckler and Koch 416 rifle among all frontline infantry units. America’s Allies in NATO and Asia, including Germany, France, the United Kingdom, Japan, and South Korea are still committed to the 5.56 round with no plans to change.