Heckler and Koch HK21A1: A belt-feed-only general-purpose machine gun

by Eric Sof

HK21A1 general-purpose machine gun

The Heckler and Koch HK21A1 was the further development of the HK21 gun, which has been in military service for years, and the aim has been to produce a one-man general-purpose machine gun that will improve the firepower of the infantry squad without adding to their logistic load. As well as being the squad light gun it can be tripod-mounted and uses as a company support weapon.


The layout of the gun is similar to the company’s rifle design, and it uses the same roller-locked delayed blowback breech mechanism. A major change has been to do away with the magazine-loading option and make this a belt-fed-only gun. The belt feed unit has been redesigned to make belt loading much quicker than previously.

A schematic of the Heckler and Koch roller-delayed blowback mechanism
A schematic of the Heckler and Koch roller-delayed blowback mechanism (Photo: Heckler & Koch)

The barrel can be quickly changed by cocking the weapon, releasing the barrel latch, and then easing the barrel forward and sideways through a slot in the ventilated barrel guard. There is a bipod that can be mounted in the usual place, at the front end of the jacket, or can be moved to a position, at the center of the balance, if preferred.

HK21A1 is based on the Heckler and Koch HK21
HK21A1 is based on the Heckler and Koch HK21 (Photo: XY)

A variety of specialized mountings are available; there is a spring-buffered tripod with panoramic sight for support fire roles; a column mount that fits on light vehicles and uses spring balancing gear to take the weight of the gun; and two different 360 degrees tracks for ground, vehicle or anti-aircraft defense.


Since then, the HK21 was offered in two main variants: the HK21A1 general-purpose machine gun (with a different belt feed mechanism) and the HK11A1 automatic rifle (optimized for magazine feed only). The HK11A1 proved more successful in export sales and was adopted by the Hellenic Army and several African and Asian armies. Both weapons, as in the original HK21, can be converted to chamber the 5.56×45mm NATO round by replacing the appropriate components.

The Heckler and Koch HK21A1 machine gun are understood to have been adopted by several African and Asian armies, but no firm details have been released.

Technical specifications

Manufacturer: Heckler & Koch GmbH, D-7238 Oberndorf/Neckar, Germany
Designed: 1961
Service: 1961-present
Type: delayed blowback general-purpose automatic
Caliber:  7.62mm NATO
Barrel: 17.7 in (450 mm)
Weight (empty): 17.63 lbs (8 kg)
Effective firing range: 100-1200 m (109–1,312 yd) sight adjustments
Rate of fire: 900 rounds per minute
Magazine capacity: belt-feed-only
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