Heckler & Koch HK21

From Wikipedia, the free encyclopedia

Heckler & Koch HK21
Type	General purpose machine gun
Place of origin	West Germany
Production history
Designer	Heckler & Koch
Designed	1961
Manufacturer	Heckler & Koch
Variants	See variants
Specifications
Weight	7.92 kg (HK21) 8.30 kg (HK21A1) 7.70 kg (HK11A1) 9.30 kg (HK21E) 8.15 kg (HK11E) 8.75 kg (HK32E) 8.00 kg (HK13E)
Length	1,021 mm (HK21) 1,030 mm (HK21A1, HK11A1, HK11E, HK23E, HK13E) 1,140 mm (HK21E)
Barrel length	450 mm (HK21, HK21A1, HK11A1, HK11E, HK23E, HK13E) 560 mm (HK21E)

Cartridge	7.62x51mm NATO (HK21, HK21A1, HK11A1, HK21E, HK11E) 5.56x45mm NATO (HK23E, HK13E)
Action	Roller-delayed blowback
Rate of fire	900 rounds/min (HK21, HK21A1) 800 rounds/min (HK11A1, HK21E, HK11E) 750 rounds/min (HK23E, HK13E)
Muzzle velocity	800 m/s (HK21, HK21A1, HK11A1, HK11E) 840 m/s (HK21E) 910 m/s (HK23E, HK13E using the SS109 cartridge)
Effective range	100 to 1,200 m sight adjustments, graduated every 100 m
Feed system	M13, DM6, DM1 ammunition belt
Sights	Rear: rotary diopter; front: hooded post

The HK21 is a 7.62 mm general purpose machine gun of German design, introduced in 1961 by Heckler & Koch based on the 7.62 mm G3 automatic rifle. It uses the 7.62x51mm NATO rifle cartridge. The weapon is in use with the armed forces of several Latin American, African and Asian countries. It was also manufactured under license by INDEP in Portugal as the Metralhadora 7,62 mm m/968 and in Mexico by SEDENA as the MG21.

1 Operation
2 Manufacture
- 2.1 HK21E
3 Service
4 See also
5 References
6 External links

[edit] Operation

The method of operation of the HK21 is the same as that used in the G3 rifle, employing a two-part breech block and delay rollers. The delayed blowback system, with a fluted chamber for easy cartridge movement, operates from the closed bolt position with a round in the chamber when the gun is ready to fire. Ammunition for HK21 is usually carried in disintegrating link belts. The gun will function using either the German DM 60 belt, the American M13 belt, or the French belt; however, the continuous link belt DM 1 can also be used if required. Furthermore, by changing the barrel, the belt feed plate, and the bolt, the gun can be converted to firing the 5.56x45mm NATO or the 7.62x39mm cartridge.

The utility of the weapon is further increased by inserting a magazine adaptor in place of the feed mechanism. This takes any of the proprietary Heckler & Koch 7.62 mm box magazines intended for the G3 rifle or the HK11 automatic rifle. If required, the belt feed unit can be withdrawn altogether and replaced with a magazine unit which fits into the receiver and is held by two locking pins. The unit allows the use of the HK11's 20-round box magazine or 80-round double-lobed drum magazine.

[edit] Manufacture

Both the HK21 and HK21A1 models are currently discontinued by Heckler & Koch, but are still manufactured under licence in Mexico, Portugal and Greece. Currently, Heckler & Koch manufactures two improved models: the HK21E, chambered in 7.62x51mm NATO, and the HK23E, chambered in 5.56x45mm NATO. The HK23E is similar to the HK21E in every respect except for the chambering and barrel length. The most major updates over the 21A1 are a slightly lengthened receiver, a fire control block with semi-auto, 3-round bursts and full-auto modes of fire, a special bolt closing device for quiet bolt closure, and a redesigned belt-feeding mechanism (the belt feed mechanism smoothly feeds the belted ammunition in two stages, during the rearward and the forward movement of the bolt). The ability to use G3 or STANAG (for HK23E) box or drum magazines is available with an optional feed module kit that consists of the bolt, recoil spring and belt feed module or magazine well. The HK21E has rear drum sights graduated up to 1200 meters and up to 1000 meters for HK23E; both sights are adjustable for windage.

[edit] HK21E

The HK21E mainstay uses a roller locked bolt and fires a 7.62x51mm NATO caliber round. It has belt-feeding capabilities and fills the role of a squad automatic weapon. Most versions of the HK21E had three-round burst trigger groups, so a three-round burst mode was available. The HK21E started as the HK21, a simple machine gun using the same caliber rounds. Then came the HK21A1, which featured some other minor modifications. The E in HK21E simply stands for Export. It was tuned until it fit American import standards before it was imported.