General Dynamics Lightweight Medium Machine Gun

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Lightweight Medium Machine Gun prototype with Trijicon TA648MGO-M2 6x48 ACOG scope - .338 Norma Magnum

The General Dynamics Lightweight Medium Machine Gun (LWMMG) is a prototype gas-operated open-bolt general-purpose machine gun (since that is what a "lightweight medium machine gun" is) chambered in .338 Norma Magnum. It is mechanically based on a patented system called "short recoil impulse averaging," a recoil-mitigating technology derived from the "differential firing" mechanism developed for the cancelled XM806 and XM307 & XM312. In both systems a large part of the gun's mechanism including the barrel and gas system (save on the recoil-operated XM806) reciprocates during firing and shots are timed to occur when the group is moving forward, forcing recoil to first overcome the momentum of the forward-moving component group. It seems General Dynamics has finally solved the rate-of-fire issues that plagued past iterations of this technology, and while the rate of fire is still at the low end of the scale for a machine gun, it is almost doubled from the XM806 and similar to that of a Browning M2. Because of this technology, it has similar felt recoil to the M240 Machine Gun despite being the same weight as the M240L and almost six pounds lighter than the M240B while firing a much more powerful round.

It was developed in-house by General Dynamics based on the experiences of US forces in Afghanistan around 2010, who were finding their M240s had issues countering insurgent forces using PKMs, particularly when ambushed from high ground at extreme range where the 7.62mm NATO round drifts noticeably more than the 7.62x54mmR. The goal of the project was to develop a weapon with the effective range of a heavy machine gun while retaining the portability of a GPMG.

The .338 Norma Magnum is a Swedish-manufactured precision rifle cartridge originally designed by American sport shooter Jimmie Sloan with the help of Dave Kiff of Pacific Tool and Gauge. It fires a 300-grain projectile with over 4,600 foot-pounds of muzzle energy: it is four times more powerful than 7.62mm NATO at 1,000 yards (though on the downside both the rounds and belt links are twice as heavy), and more accurate at range than both 7.62mm NATO and .50 BMG. The concept of a machine gun firing a round intermediate between rifle and true heavy machine gun is not a new one: there was a brief fad for such weapons in the 1930s, resulting in what could be termed "heavy medium" machine guns chambered for rounds like 8x59mmRB Breda.

In May 2017, the United States Marine Corps and SOCOM issued a Sources Sought Solicitation for 5,000 machine guns chambered for a polymer-cased .338 Norma Magnum cartridge, weighing 24 pounds or less with a 24-inch quick-change barrel with the option of a suppressed barrel, compatible with the existing M192 tripod and fitted with a lightweight bipod, with a rate of fire of 500-600 rpm and a range against area targets of no less than 2,000 yards. Currently, the GD LWMMG and the SIG-Sauer MG 338 are the two main machine gun designs in this caliber. The LWMMG is designed specifically with replacing the M240 in mind and requires no alteration to existing M240 mountings in order to fit on them.

Specifications

(Prototype, first displayed 2012, suppressed version demonstrated 2014)

  • Type: General-purpose machine gun
  • Caliber(s): .338 Norma Magnum (8.6x63mm)
  • Weight: 24 lbs (10.9 kg) (first prototypes), 105 lbs (47.6 kg) (complete shippable first variant with M192 tripod, 500 rounds of ammunition, spare barrel and ACOG optic), 22 lbs (10 kg) (current model)
  • Length: 49 in (124.5 cm)
  • Barrel length(s): 24 in (61 cm)
  • Capacity: Belt-fed, usually 50 round soft pack or 100 round belt box
  • Fire Modes: Safe / semi / auto (500rpm)

The General Dynamics Lightweight Medium Machine Gun appears in the following movies, TV shows, and video games:

Video Games

Game Title Appears as Mods Notation Release Date
ArmA III SPMG .338 Marksmen DLC 2013




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