Heckler & Koch HK 21

Heckler & Koch HK 21 History

In 1949, Heckler & Koch GmbH was founded in Oberndorf am Neckar, West Germany, as a designer and manufacturer of small arms. Today, HK is one of the world's top manufacturers of small arms, with a product line that includes battle rifles, assault rifles, submachine guns, personal defense weapons, marksman rifles, sniper rifles and various air-cooled machine guns. HK saw an opportunity in 1961 and started designing a new "universal" machine gun, this development became the "HK21" series.

The HK 21 was officially classified as a "General Purpose Machine Gun" (GPMG) - although it was also considered a "Light Machine Gun" (LMG) - which later became a family of supporting weapons. The series was based on the very successful HK G3 battle rifle/assault rifle, which was later widely used around the world. The original G3 automatic rifle design used a 20-round straight detachable magazine, and a 50-round drum to assist fire.

As the HK21 descends from the G3, the HK21 uses a similar receiver, can be operated from a magazine or belt feed, and includes a detachable bipod for stabilization in fire support roles.

The HK21 was originally designed as a belt gun, but an adapter was made to allow the use of a cassette magazine or ammo drum. All Heckler & Koch machine guns (including the HK21) have the same successful barrel delayed recoil action - based on the original StG45 prototype from late WWII - with a fixed barrel. A two-piece breech block and roller retard are standard, while smooth extraction is due to the grooved cavity. Shooting action is sequenced by a two-position lever to allow semi-automatic single-shot or fully automatic fire.

If the operator wants to fire 7.62x39mm or standard 5.56x45mm cartridges, simply changing the barrel, feed plate and breech is enough to create an entirely new weapon platform. To prevent the bolt from hitting the barrel at an angle and reset the locking assembly, a spring-loaded extractor was used.

The recoil bolt uses the energy of the previous shot and extracts the cartridge through this lever ejection system. The selector switch is clearly marked with "E" for semi-automatic fire and "F" for fully automatic fire, and turning the joystick to the "0" or "S" setting will prevent the fire from entering the "safe" mode switch.

To accommodate a range of multiple ammunition delivery systems, HK has also developed a module that allows the use of German DM6 and DM1 conveyor belts, as well as American M13 conveyor belts. The module is mounted under the gun with the bolt passing through the ammo belt - upside down, so the link points down. The new cartridge is then put in place by the reciprocating motion of the bolt.

A heavy-duty barrel with muzzle flash suppression is standard, as are adjustable iron sights consisting of front and rear sights, with rear sights ranging from 100 m to 1200 m in 100 m increments. The HK21 received a fixed but adjustable and removable polymer stock. A foldable carrying handle is provided in the center of the weapon for easy transport of the entire weapon.

In addition to a bipod, the HK 21 can also be attached to a tripod or vehicle socket mount.

After a period of actual combat, the HK21 line was simplified and improved to become the HK21A1 in the 1970s. The HK11 series is similar to the HK21, but differs only in the magazine feed and automatic rifle classifications. The HK21E is an export model that holds the 7.62x51mm NATO cartridge. The HK23E is an export light machine gun chambered for the 5.56x45mm NATO cartridge.

The HK13E is another automatic rifle development that is magazine loaded with 5.56x45mm NATO cartridges. The HK G8 offers telescopic sights, quick-change barrels and a variety of box magazines, as well as ammo counts for drum magazines.

HK GR-6 and GR-9 were issued to special forces and their serial numbers were removed. GR-6 stands for automatic rifle form, while GR-9 is for light machine gun form.

Portugal produced the HK21 under license as m/986, while Mexico designated its local variant (HK21E) as the MG21 produced by SEDENA.

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