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Fabrique Nationale Mk 46 LWMG

Light Weight Machine Gun

Infantry / Small Arms

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Image courtesy the United States Department of Defense

The Mk 46 Light Weight Machine Gun was developed to USSOCOM specifications utilizing the 5.56mm NATO cartridge.

Authored By: Staff Writer | Last Edited: 5/22/2018 | Content ©www.MilitaryFactory.com
In the early 2000s, USSOCOM (United States Special Operations COMmand) began a program to replace its long-running Mk 43 Mod 0 Light Machine Gun (LMG). The Mk 43 was a specialized, portable form of the Vietnam-era M60 General Purpose Machine Gun (GPMG) through the M60E4 variant, retaining the gas-operation and 7.62x51mm NATO belt-fed cartridge. The Mk 43 improved upon reliability of the M60 series and was given iron sights, a folding bipod and a forward vertical hand grip for additional support. However, reliability was never truly resolved and higher portability was required of a more modern system. This gave rise to the "Light Weight Machine Gun" program under the direction of United States Naval Special Warfare Command (US NSWC) and partnered through the Belgian concern of Fabrique Nationale which produced an off-shoot of the successful M249 SAW (Squad Automatic Weapon), itself based on the Fabrique Nationale Minimi family. The new product became the "Mk 46 Mod 0", a gas-operated automatic weapon feeding from the US M13 disintegrating belt and chambered for the 5.56x45mm NATO cartridge. Similarly, the dimensionally larger Mk 48 was developed concurrently for special forces use and chambered for the larger rifle-caliber 7.62x51mm NATO cartridge.

The Mk 46 was based specifically on the M249 SPW (Special Purpose Weapon) variant of the M249 line. The M249 SPW was given a shorter barrel and forend and lacked the standard carrying handle, vehicle mounts and magazine well of the original M249 offering which lightened the design to an extent and, thusly, made it more portable. Unlike the SPW with its collapsible stock, the Mk 46 was instead given the formed shoulder stock of the original M249 production model. MIL-STD 1913 rails (located at the sides and underside of the forend and along the top of the receiver) were added to broaden the tactical nature of the weapon and allow for various optics and accessories to be fitted as required. A bipod could be optionally fitted ahead of the forend/heat shield for additional frontal support required in the suppression fire role.

The M46 action relies on an open-bolt operation and features a changeable barrel assembly to prevent overheating and subsequent fracturing. The weapon is coated in a non-reflective black finish to protect the operator from glint while the bipod is of lightweight, though heavy-duty, titanium to content with the abuses of the modern battlefield. The receiver itself is of a formed steel frame construction while the barrel is of hammer-forged steel with a hard chrome-plated bore (as is the internal chamber). The buttstock is completed from lightweight polymers and ergonomically. An optional telescoping metal buttstock can be fitted that includes a hydraulic recoil buffer system and non-slip buttplate. The trigger guard is oversized for gloved hand operation. A carrying handle, affixed above the heat shield, is optional.

The Mk 46 provides the special warfighter with a compact, portable and adaptable high-volume automatic weapon system. Its belt-fed nature means that the Mk 46 operator can provide voluminous fire at range in both the direct contact and suppression fire roles, additionally accurized by way of available aimers and optics. The use of 5.56x45mm ammunition also makes for a logistically-friendly complement to the M4 Carbine and M16 assault rifles currently in widespread use by the US military and others. Additionally, the larger Mk 48 itself complements the Mk 46 when the larger rifle-caliber 7.62x51mm cartridge and its longer-range penetrative capabilities are required. The Mk 46 has gone on to become a proven performer under extreme circumstances across both open field and urban environments.

The Mk 46 sports an effective range of 800 meters against point targets with a maximum range of 1,800 meters against a target area. The system's overall length is 36.22 inches with an overall empty weight of 15.44lbs. Its listed cyclic rate-of-fire is 730 rounds-per-minute.

As of this writing, USSOCOM is the only recognized operator of the Mk 46 LWMG. The MK 46 Mod 1 is an updated version of the original Mk 46 Mod 0 model.


Fabrique Nationale - Belgium
National flag of United States United States
- Fire Support / Suppression / Defense
Overall Length:
919 mm (36.18 in)
Barrel Length:
414 mm (16.30 in)
Weight (Unloaded):
15.43 lb (7.00 kg)
Iron; Optional Optics
Gas-Operated; Open Bolt; Full-Automatic
Muzzle Velocity:
5,900 feet-per-second (1,798 meters-per-second)
730 rounds-per-minute
Mk 46 Mod 0 - Base Series Designation; chambered for the 5.56x45mm NATO cartridge through disintegrating belt feed.
Mk 46 Mod 1 - Updated version of the Mk 46 Mod 0
Mk 48 Mod 0 - 7.62x51mm NATO variant

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