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Heckler & Koch HK121 (MG5)

General Purpose Machine Gun (GPMG) Project [ 2005 ]

The Heckler and Koch HK121 GPMG was adopted as the MG5 by the German Army in 2005 and is the direct successor to the storied Cold War-era MG3 series.

Authored By: Staff Writer | Last Edited: 08/16/2023 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The Heckler & Koch HK121 fulfills the General Purpose Machine Gun (GPMG) product slot for German gunmaker Heckler & Koch. It stands as a 7.62x51mm NATO-chambered offshoot of the 5.56x45mm HK MG4 squad automatic weapon. At its core is a proven gas-operated system performing at 600 to 800 rounds-per-minute with feeding from an ammunition belt. Effective range reaches out to 600 meters with a maximum range double that - sighting through a standard diopter arrangement or iron sights. The weapon exhibits a weight of 10.8 kilograms and length of 1,165mm with a barrel length of 550mm while also showcasing very little observable recoil when fired. The HK 121 has been adopted in limited numbers by the German Army since 2005 and is intended to replace the MG3 GPMG line, itself a post-World War 2 (1939-1945) development of the MG42.

MG5 is the official German Army designation for the HK121

As a GPMG, the HK121 follows accepted practice as a belt-fed, air-cooled multi-use weapon. It can be fired from the shoulder with support from a shoulder strap and foregrip, along the ground through use of a folding bipod, from a tripod assembly or from a vehicle as a suppression weapon. The design is dominated by a large rectangular receiver with an optional shoulder stock while the pistol grip and trigger unit are integral. Along the top of the receiver is a length of rail for the adoption of various optics and night vision accessories to suit both customer requirements and mission needs. The barrel is of a "quick-change" design which is required of a good air-cooled machine gun and the included carrying handle aids in its changing for a process lasting just seconds. The gas cylinder sits under the barrel in the usual way.

Vehicle versions lose the full shoulder stock and are given spade grips that interact direction with the trigger unit (the pistol grip is still retained). Portability for the infantryman is broadened by use of the shoulder strap with vertical foregrip or by way of the folding bipod. The heavy-duty tripod allows the weapon a very stable gunnery platform that reduces recoil to nil. As a belt-fed weapon, the HK 121 can use exposed ammunition belts, a 50-round drum container or a 120-round box as a feeding sourcing. Robustness is key with the HK121 product, its operation suffering not when even fully submersed in water and fired thereafter - with no degradation of the action.

The HK121 certainly has large shoes to fill as the MG3 is a proven winner and has been adopted in large numbers by many world armies while also license-produced by local factories is several countries.©MilitaryFactory.com
Note: The above text is EXCLUSIVE to the site www.MilitaryFactory.com. It is the product of many hours of research and work made possible with the help of contributors, veterans, insiders, and topic specialists. If you happen upon this text anywhere else on the internet or in print, please let us know at MilitaryFactory AT gmail DOT com so that we may take appropriate action against the offender / offending site and continue to protect this original work.


Service Year

Germany national flag graphic


General Purpose Machine Gun (GPMG) Project

Heckler & Koch GmbH - Germany
(View other Arms-Related Manufacturers)
National flag of modern Germany Germany
(OPERATORS list includes past, present, and future operators when applicable)
Fire Support
Capable of suppressing enemy elements at range through direct or in-direct fire.

Overall Length
1,165 mm
45.87 in
Barrel Length
550 mm
21.65 in
Empty Wgt
23.81 lb
10.80 kg

Diopter Sight


Gas-Operated; Full-Automatic Fire Only

Rounds are automatically ejected from the breech, a new cartridge stripped from the feed and set in the chamber, and rounds are continuously fired so long as the trigger is pulled and an ammunition supply exists.
Gas-operated system is featured, typically involving a gas cylinder and rear-driven piston directing energy to the bolt component.
(Material presented above is for historical and entertainment value and should not be construed as usable for hardware restoration, maintenance, or general operation - always consult official manufacturer sources for such information)


7.62x51mm NATO

Sample Visuals**

Graphical image of a 7.62x51mm / .308 Winchester rifle cartridge
Rounds / Feed

50-round belt or drum; 120-round belt box
Cartridge relative size chart
*May not represent an exhuastive list; calibers are model-specific dependent, always consult official manufacturer sources.
**Graphics not to actual size; not all cartridges may be represented visually; graphics intended for general reference only.
Max Eff.Range
1,970 ft
(600 m | 657 yd)
Muzzle Velocity
2,656 ft/sec
(810 m/sec)

HK 121 - Base Company Designation; model of 2010; 7,114 procured by German Army for initial evaluation.
MG5 - German Army designation.

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Images Gallery

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Image of the Heckler & Koch HK121 (MG5)
Image from the US DoD DVIDS imagery database; Public Release.

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