The XM312 made up the infantry heavy machine gun portion of the now-canceled XM307 Automatic Grenade Launcher
Authored By: Staff Writer | Last Edited:
At one point, the General Dynamics XM312 was being developed to replace the venerable and tenured - yet aging - Browning M2HB heavy machine gun in service with the United States military. Design work was headed by General Dynamics as part of the Joint Services Small Arms Program beginning in 2000 which ultimately yielded a working prototype in 2004. The XM312 was to serve alongside the proposed XM307 "Advanced Crew Served Weapon" (ACSW), a 25mm belt-fed grenade launcher. The XM312 was to become the 12.7mm (.50 BMG) heavy machine gun component in the new endeavor as both were completed with commonality of parts allowing each system to be converted to the other with some modification by the crew. In this fashion, the combined weapon system would prove logistically friendly to the US military in the long term. However, both the XM307 and XM312 were cancelled as the US military refocused its efforts on procuring their tried-and-true Browning M2 machine gun and Mk 19 automatic grenade launcher - more cost feasible solutions at the time.
Undoubtedly, the XM312 was a futuristic-looking weapon and the next logical evolution of the heavy machine gun platform. The weapon's physical characteristics included a smooth-contoured receiver sporting a molded shroud. The barrel protruded a distance away from the shroud and noticeably lacked a muzzle brake. Ammunition was fed via a belt which was held in a hard box fitted along the left side of the receiver, ejected through a port at the right side. Sighting was through a flip-up assembly at the rear of the receiver or through (optional) optics allowing for much improved ranged accuracy. The weapon would be typically fitted to a heavy-duty adjustable tripod mounting or a vehicle pintle. The entire weapon system weighed a hefty 52lbs and featured a running length of 61.4 inches with 36 inch barrel in place. A standard operating crew was two personnel - one to manage the firing function and the other manage the ammunition supply, help to clear stoppages and change out an overheated barrel as required.
The XM312 initially relied on a gas and recoil system of operation. The gas actuated the bolt as the recoil action managed the feed. When this proved unreliable in testing, it was deemed to make the weapon fully recoil-operated (as in the Browning M2). The action allowed for a cyclic rate-of-fire of 260 rounds per minute to be achieved with 40 rounds through sustained action before requiring a change of barrel. Maximum range during testing reached 2,000 meters.
As in the XM312, the General Dynamics XM806 - another 12.7mm heavy machine gun development appearing in 2009 - failed to unseat the famous Browning M2 series. This development was cancelled in 2012.
Manufacturing General Dynamics - USA
United States (cancelled)
- Fire Support / Suppression / Defense
1,560 mm (61.42 in)
914 mm (35.98 in)
41.89 lb (19.00 kg)
Basic Iron; Optional Optics
Recoil-Operated; Rotating Bolt; Belt-Feed
6,560 ft (1,999 m; 2,187 yd)
XM312 - Base Series Designation for advanced prototypes.
XM307 - 25mm Automatic Grenade Launcher Prototype on which the XM312 was based on.
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