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Heckler & Koch HK 21
Despite its 1960s origins, the HK 21 general purpose machine gun is still in use around the globe today.
By JR Potts, AUS 173d AB
HK (or Heckler & Koch) is a small arms weapons designer and manufacturer owned by the British company, BAE Systems, though the company itself is located in Oberndorf Neckar, Germany. HK is one of the world’s finest small arms producers whose product line delves into assault rifles, submachine guns and various air-cooled machine guns. HK saw an opportunity in 1961 to branch out and design a new universal machine gun, with this design becoming the HK 21. The HK 21 fell into the general purpose light machine gun family and used the stellar G3 automatic rifle as a model. The G3 automatic rifle design used a 20-round box magazine or a 50-round drum. As the G3 was the blueprint for the HK 21, the HK 21 used a similar receiver along with a detachable bipod.
The HK 21 was designed to be belt-fed however an adapter was produced to allow the use of box magazines or an ammunition drum. All Heckler & Koch machine guns (including the HK 21) feature the same successful delayed blowback action with a stationary barrel. A two-part breech block and roller delays were standard with smooth extraction was due to a fluted chamber. The firing action was sequenced by a two-position lever to accept single rounds or allow for full automatic fire. If the operator wanted to fire the 7.62x39mm or the 5.56x45mm round a simple change of barrel, feed plate and the bolt would suffice. To prevent the bolt from striking obliquely against the barrel and return the locking assembly, a spring-powered extractor was used. The recoiling bolt utilized energy from a shot and would extract the cartridge via this lever ejector system. The selector switch was labeled with an “E” for semi-automatic fire, an “F” for full automatic fire and rotating the lever to the 0 or S setting would block firing to a "safe" mode.
To accept a number of multiple ammunition feed systems HK devised a module to allow use of the German DM6 and DM1 belt and the American M13 belt. The module was fitted below the weapon in which the bolt would pass over the ammo belt - set upside down so the links face down. The new round was then fed into position by the reciprocating action of the bolt. A heavy barrel with a flash suppressor was standard as were iron adjustable sights, this consisting of a forward and rear sight with the rear sight ranging from 100m to 1200m in 100m increments. The HK21 was given a fixed though adjustable and removable polymer stock. A collapsible carrying handle located in the center mass was provided for easy carrying of the weapon. In addition to a bipod, the HK 21 could be affixed to a tripod or vehicle, the latter via a pintle mount.
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Last Updated: 4/22/2009
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| Specifications for the Heckler & Koch HK 21 |
Operation: |
Action: Delayed Blowback; Selective Fire
Cartridge: 7.62x51mm
Feed System: Metal Link Belt
Muzzle Velocity: 2,700ft/sec (823m/sec)
Cyclic Rate-of-Fire: 900 rds/min
Effective Range: 6,600ft (2,012m; 2,200yds)
Sights: Hooded Front Post; Rear Rotary Diopter Drum
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Dimensions: |
Overall Length: 1,020mm (40.16in)
Barrel Length: 450mm (17.72in)
Empty Weight: 7.3kg (16.09lbs)
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| Variants |
HK 21 - Base General Purpose Machine Gun
HK 21A1 - General Purpose Machine Gun; simplified production model; revised feed mechanism; increased weight; carrying handle; hooked-style buttstock; magazine and belt feed.
HK 11A1 - Automatic Rifle; magazine feed only.
HK 21E - Modernized HK 21; general purpose machine gun; belt fed; chambered for 7.62x51mm NATO round; export model.
HK 11E - Modernized HK 11; automatic rifle ; magazine fed; chambered for 7.62x51mm NATO round; export model.
HK 23E - Light Machine Gun; belt-fed; chambered for 5.56x45mm NATO round; export model.
HK 13E - Automatic Rifle; magazine fed; chambered for 5.56x45mm NATO round; export model.
G8 / Gewehr G8 - Telescopic sights; quick-change barrel; bipod; 10- or 20-round box magazines OR 50-round drum.
G8A1 / Gewehr G8A1 - Based on the HK 11A1 model; magazine and drum feeds.
GR-6 - Automatic rifle based on the HK 13; sans serial numbers and iron sights; optical sights; wood and desert camouflage patterns.
GR-9 - Light machine gun based on the HK 23; sans serial numbers and iron sights; optical sights; wood and desert camouflage patterns.
m/968 - Portuguese license-production HK 21 under Fabrica do Braco de Prata.
MG21 - Mexican license-production HK 21E under SEDENA.
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