Of the companies competing to build the U.S. Army's next standard infantry rifle and squad automatic rifle, both of which will use new 6.8mm ammunition, only one offering has a so-called bullpup configuration where the main action is positioned behind the pistol grip. There are benefits to this arrangement, namely the ability to maintain the accuracy that a longer barrel offers in a more compact package, but the U.S. military as a whole has rejected them in the past in favor of more traditional designs. General Dynamics Ordnance and Tactical Systems (GD-OTS) first unveiled its RM277 small arms line at the Association of the U.S. Army's main annual convention in Washington, D.C., which opened on Oct. 14, 2019, and wrapped up today. The Firearms Blog was first to report the guns' designation, as well as other details about the particular features of the infantry rifle and automatic rifle variants that have emerged so far. However, GD-OTS has been relatively tight-lipped about the weapons, which are competing in the Army's Next Generation Squad Weapons (NGSW) program, which aims to replace the service's 5.56mm M4 carbines and M249 Squad Automatic Weapons (SAW). The company told The Firearms Blog that its policy is not to issue formal press releases regarding systems taking part in "an active, open competition."

As noted, the basic design of both RM277 variants is a bullpup with the action, along with the magazine, situated all the way to the rear. They both also feature a large top-mounted rail for optics, night and thermal vision systems, and other accessories. There are back up sights offset to the side and there appear to be attachment points for additional rails on the sides and underneath the forend handguard. The automatic rifle variant, which has a folding bipod, has a slightly longer barrel than the rifle version, but we don't yet know the exact dimensions of either model. The barrel on the automatic rifle version, intended for more sustained fire, is clearly fluted to reduce weight and help it cool faster. It is possible the one in the basic rifle design is, as well, and it is just not visible.

GD-OTS via The Firearms Blog GD-OTS' RM277 automatic rifle variant, at top, and infantry rifle version, at bottom.

Both guns fire a 6.8mm round, with a polymer case rather than a brass one to keep weight down, that ammunition maker True Velocity developed to go along with the guns. All of the NGSW entrants will have to be chambered in this caliber. 6.8mm is roughly .277 caliber, which is the origin of the "277" in the RM277 designation. The U.S. military has been exploring polymer cases for years as a way to reduce how much weight individuals troops have to carry and it has begun to buy such ammunition, and rounds that use hybrid polymer-metal cases, already. These developments are extremely innovative and notable in their own right.

True Velocity True Velocity's 6.8mm cartridge design.