HK 21

The HK 21 along with all its variants is without a shadow of a doubt, one of the most adaptable and flexible weapons of its class. So successful is the unique modular design of the HK 21 that any number of configurations are possible to make it suit a variety of functions. It is a General Purpose Machine Gun par excellence. In fact the weapon that started out as a modified G3 assault rifle has evolved into a GPMG that is appreciated for its capabilities and functionality by special units the world over.

The earliest HK 21 had its fair share of problems and hitches due to the fact that it was a modified assault rifle with a delayed blowback system, altered to a belt fed machine gun. The delayed blowback system using a two part breechblock and delay rollers and operating from a closed bolt position is commonly a feature of all HK variants. The fluted chamber actually helps to push the cartridge case ensuring that the extraction is smooth and positive. The early HK 21 suffered part breakages, buffer problems and other structural problems, which were subsequently ironed out. But the modular design is so flexible and adaptable that by merely swapping the barrel, feed unit and bolt group it can be converted to two different calibers i.e 7.62 x 52 mm NATO and 5.56 x 45 mm NATO. It can be adapted to use any Heckler &Koch magazine instead of a belt feed just by installing an adaptor. Usually though, the HK 21 is fed by a disintegrating link belt, either a German DM 60 belt, a US M13 belt or a French belt. All of these adaptations can be accomplished at the operator level without requirement of any tools and can be done quickly. The selector lever for choosing between single shot, fully automatic or safety is located above the pistol grip and trigger mechanism. The HK 21 can be fired from an integral bipod or a mounted tripod.

Special units like the US Army's Delta Force to rescue American Hostages in Iran during Operation Eagle Claw in 1980 have used the HK 21. The HK 21 and its later variant the HK 21 A1 (which is belt fed only) are still currently in service with African and South East Asian countries and continue to be manufactured under license in Portugal and Greece. Heckler & Koch have themselves discontinued their production.

The HK 21 E is the current variant on the original weapon that Heckler & Koch do manufacture. The HK 21 E is a vastly improved weapon in which all of the glitches of the HK 21 have been fixed. The length of the receiver has been increased to allow for an additional recoil length for the bolt group and reinforcing bars have been added to the receiver to strengthen it. A complete redesign of the bolt carrier, recoil spring, bolt head, belt feed unit, barrel and trigger group, extractor and locking roller holder has been done. This makes the HK 21 E a vastly superior weapon than its predecessors. The HK 21 E has a rear drum sight graduated up to 1200 meters and some even consider it as the most accurate machine gun.