By Chris Upchurch, Suarez International Director of Marketing
Soon after HK began producing the G3 battle rifle for the Bundeswehr they began working on a machinegun design. The resulting family of weapons are still close cousins of the G3. They use the same roller delayed blowback design and many parts can be interchanged between the battle rifle and the machineguns.
While most machineguns derived from battle rifles are fed from box magazines the most common variants of the HK machineguns are the belt fed versions: the HK21 in 7.62x51mm and the HK23 in 5.56mm. Unusually for a belt fed machinegun, the belt is below the bolt, rather than above. This makes changing belts more cumbersome, but it allows the belt feed unit to be switched out for a magazine well that can accept standard G3 magazines or 50 round drums (HK33 magazines for the HK23). The switch requires only the magwell, a new bolt, and a recoil spring assembly. In this form the 7.62x51mm MG is the HK11 and the 5.56mm version is the HK13. The level of modularity extends even further, allowing the 7.62x51mm HK21 to be converted to a 5.56mm HK23 (or the box fed HK13).
The HK machineguns fire from a closed bolt. This means the barrel does not have as much opportunity to cool between shots as it does in an open bolt machinegun. Having a live round in a hot chamber does present the danger of a round ‘cooking off’ (firing due to heat, without the primer being struck by the firing pin) but heating up the gun to that degree requires around 1000 rounds of continuous fire. The closed bolt design, combined with a free floated heavy barrel makes these weapons very accurate. Sub-MOA accuracy is typical.
They are equipped with a quick change barrel, allowing a hot barrel to be swapped out for a fresh one in a matter of seconds. Unlike some other designs, only the barrel needs to be removed, as there is no gas system and the sights and bipod are attached to the charging handle tube and barrel shroud respectively.
The earlier versions came with an SEF trigger group allowing single shots or fully automatic fire. The newer HK21E adds a three-round burst option, as well as a forward assist, a new belt feeding mechanism and numerous minor improvements.
The HK21 series is light for a 7.62x51mm General Purpose Machine Gun. The original HK21 weighs in at only 17.46 pounds, with the newer HK21A1 coming int at 18.3 lbs. Compare this to the contemporary M60 at 23.5 lbs or the FN-MAG at 26 lbs.
The HK21 came along too late for widespread adoption by the Bundeswehr, which had already standardized on the MG3 (basically a 7.62x51mm version of the WWII era MG42). However, the HK11 and HK11A1 were adopted by both the Bundeswehr and the Bundesgrenzschutz (Federal Border Guards) as a designated marksman’s rifle and support weapon under the designation G8 and G8A1. There aren’t many machineguns accurate enough to be used as a DMR.
The HK21 family saw widespread adoption around the world. It served with Portugal, Mexico, Greece, Sweden, Thailand, Peru, Ecuador, and others. Generally it was adopted by nations that had also adopted the G3 or HK33, taking advantage of the commonality among the HK family of weapons. Portugal and Mexico both produced the design under license.
In the United States, the HK23 lost out to the FN Minimi (adopted as the M249) in the Squad Automatic Weapon competition in the late 1970s. However, the HK21 did see service with U.S. Special Operations units, including Delta Force, which deployed them during Operation Eagle Claw, the 1980 attempt to rescue American hostages in Iran.
More than any other area of the HK family, the machineguns highlight the modularity of the design. The ability to go between calibers as well as between belt and box fed just by changing out a few parts is really quite amazing.
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