CrazySanMan
2013'er
This Exotic Bullpup Rifle Is Competing To Replace The Army's M4 Carbines And M249 SAWs
https://www.thedrive.com/the-war-zone/30472/this-exotic-bullpup-rifle-is-competing-to-replace-the-armys-m4-carbines-and-m249-saws
https://www.thedrive.com/the-war-zone/30472/this-exotic-bullpup-rifle-is-competing-to-replace-the-armys-m4-carbines-and-m249-saws
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.
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 for the Army. 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.
Most interestingly, both guns use a novel "gas and recoil-operated, impulse averaged, air-cooled" operating mechanism, according to The Firearms Blog. It's not entirely clear how the guns function, but the description suggests that they use a combination of physical energy from firing a round, as well as propellant gas siphoned off as the bullet travels down the barrel, to cycle the action. By comparison, the U.S. Army's standard M4 carbine uses propellant gas alone.
A promotional video below shows that the barrel on the RM277 versions moves back and forth during firing, which is indicative of so-called "long recoil" designs. Though the basic concept of a long-recoil action has been around for decades, they have become increasingly rare and pairing it together with a gas system would be very unusual.
In principle, using a combination of long-recoil and gas-operated action could help mitigate felt recoil, which would improve accuracy, even during fully automatic fire. This could also help keep weight down, by minimizing the force firing each round exerts on the weapon and, in turn, reducing the need for more robust recoil system components. Combining all of this will a bullpup configuration could also ensure maximum barrel length without needing to dramatically increase the overall length of the weapon to accommodate this operating mechanism, as well.