Heckler & Koch HK 21 General Purpose Machine Gun / Light Machine Gun / Automatic Rifle (1961)
Despite its 1960s origins, the HK21 general purpose machine gun is still in use around the globe today.
The HK21 was initially designed as a belt-fed weapon however an adapter was then produced to allow the use of box magazines or an ammunition drum. All Heckler & Koch machine guns (including the HK21) feature the same successful roller-delayed blowback action - based on the original late-World War 2-era StG45 prototype - with a fixed barrel. A two-part breech block and roller delays were standard and a smooth extraction was due to a fluted chamber. The firing action was sequenced by a two-position lever to facilitate either single, semi-automatic fire or for full-automatic fire. If the operator wanted to fire the 7.62x39mm or the 5.56x45mm standard cartridge a simple change of barrel, feed plate and the bolt would suffice in creating an all-new weapon platform. To prevent the bolt from striking obliquely against the barrel and return the lock assembly, a spring-powered extractor was used. The recoiling bolt utilized energy from the preceding shot and would extract the cartridge via this lever ejector system. The selector switch was labeled clearly 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 enter a "safety" mode.
To accept a number of multiple ammunition feed systems HK also devised a module to allow use of the German DM6 and DM1 belt as well as the American M13 belt. This module was fitted below the weapon in which the bolt would pass over the ammunition 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 adjustable iron 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 at the center mass of the weapon was provided for ease of transportation of the weapon in whole. In addition to a bipod, the HK 21 could be affixed to a tripod or vehicle pintle mount.
After some time in the field, the HK21 line was simplified and improved to become the HK21A1 in the 1970s. The HK11 series was similar to the HK21 though differentiated by its magazine-only feed and classification as an automatic rifle. The HK21E was an export model chambered for the 7.62x51mm NATO cartridge. The HK23E was an export light machine gun chambered for the 5.56x45mm NATO cartridge. The HK13E was another automatic rifle development and fed by magazines holding 5.56x45mm NATO cartridges. The HK G8 offered telescopic sights, a quick-change barrel and various box magazine and one drum magazine ammunition count. The HK GR-6 and GR-9 were issued to special forces units and had their serial identifiers removed. The GR-6 represented the automatic rifle form while the GR-9 was the light machine gun form.
Portugal license-produced the HK21 as the m/986 while Mexico designated their local variants (HK21E) as the MG21 with production by SEDENA. Text ©2003-2013 www.MilitaryFactory.com • All Rights Reserved • No Reproduction Permitted
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Specifications for the
Heckler & Koch HK 21
General Purpose Machine Gun / Light Machine Gun / Automatic Rifle
Country of Origin: Germany
Manufacturer: Heckler & Koch GmbH - Germany / SEDENA - Mexico / Fabrica do Braco de Prata - Portugal
Initial Year of Service: 1961
Overall Length: 1020mm (40.16in)
Barrel Length: 450.00mm (17.72in)
Weight (Empty): 16.09lbs (7.30kg)
Cartridge: 7.62x51mm NATO; 5.56x45mm NATO
Action: Delayed Blowback; Selective Fire
Feed: Metal Link Belt; 10- or 20-round box magazine; 50-round drum
Muzzle Velocity: 2,700ft/sec (823m/sec)
Rate-of-Fire: 900 rounds per minute
Range: 6,600ft (2,012m; 2,200yds)
Sights: Hooded Front Post; Rear Rotary Diopter Drum
Variants:
HK21 - Base General Purpose Machine Gun
HK21A1 - General Purpose Machine Gun; simplified production model; revised feed mechanism; increased weight; carrying handle; hooked-style buttstock; magazine and belt feed.
HK11A1 - Automatic Rifle; magazine feed only.
HK21E - Modernized HK 21; general purpose machine gun; belt fed; chambered for 7.62x51mm NATO round; export model.
HK11E - Modernized HK 11; automatic rifle; magazine fed; chambered for 7.62x51mm NATO round; export model.
HK23E - Light Machine Gun; belt-fed; chambered for 5.56x45mm NATO round; export model.
HK13E - Automatic Rifle; magazine fed; chambered for 5.56x45mm NATO round; export model.
HK G8 / Gewehr G8 - Telescopic sights; quick-change barrel; bipod; 10- or 20-round box magazines OR 50-round drum.
HK G8A1 / Gewehr G8A1 - Based on the HK 11A1 model; magazine and drum feeds.
HK GR-6 - Automatic rifle based on the HK 13; sans serial numbers and iron sights; optical sights; wood and desert camouflage patterns.
HK 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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