Shooting the HK21 Modular Machine Gun

The HK21 is a the belt-fed iteration of the H&K roller-delayed blowback mechanism. H&K built a wide range of firearms around that system, including submachine guns (MP5), rifles (HK33, HK91), precision rifles (PSG-1), and machine guns. Originally they made a version in 5.56mm and one in 7.62mm, but later combined both guns into a single universal platform. The standardized receiver can be fitted with either magazine-feed or belt-feed mechanisms in either 5.56mm or 7.62mm, greatly simplifying H&K’s production and logistics.

This is the 7.62mm belt fed model, which was popular with clients like Portugal who used the G3 rifle but not the MG3 machine gun. It has a reputation for unrivaled reliability under terrible maintenance and harsh environments. The downside, however, is harsher recoil than most other guns I have used in its class.

Many thanks to H&K USA for providing me access to this HK21, and to Trijicon for graciously providing use of their range and their VCOG optic!


  1. Something that could be useful to start showing in videos of mounted machine guns is how they traverse, that is how easily and effectively one can switch targets.

  2. Thanks for bringing this gun up Ian. I knew about it long time but never saw it in practical use. One thing I especially admire is how compact the feed is – far cry from overbuilt MAG58.

    Oh yeah, they also have tripod for it – you can use it almost as MG3.

    • If your going to use a tripod I think the Mg42 is better scare; the enemy into staying still and hit them with a mortar, ae someone else said Be hard to move against that; clearly folk did, and good luck to them. But theres also lots of war graves.

      • This thing is nasty! Best MG ever, in my conception of MG. What makes it so good? Function of course, but also the phenomenally efficient construction. And that density of fire! Masterpiece.

        • In my experience compares poorly to a PKM.
          Tripod is good, but is that complexity really needed today?

    • “(…)MAG58(…)”
      I would said that L7 machine gun and HK 21 differs as they are results of two completely different approaches – for first one make it work while for second provide maximal tactical possibilities using up-to-date technology. IIRC from our previous discussion HK needed more than few years to perfect this design, after introduction in early 1960s. But that is not uncommon for designs aimed to provide possibilities earlier not availability – like ability to swap between magazine-feed and belt-feed, with first option allowing also usage of high-capacity double-drum.

      • I know that the West German police had them for their road blocks. I remember seeing it used when we can joint patrols as an mp

  3. slight correction:
    Yes, the Bundeswehr does not have the HK21 in service, but there are quite a few G8 in service, which are are HK11 machineguns. Complete in a crate with the belt feed, linkless feeding device and the G3 magazine adapter. During the Cold WAr used by the Fernspäher (LRRP) and Kampfschwimmer (combat divers) and a few other small special units. Today also still in use with the KSK. There often in a cross-over DMR/automatic rifle role with a scope and magazine feed. there are photos out there of KSK patrols with the G8. Friend of mine has oraganized a reservist training in the Black Forest and thought “just do it” and asked the KSK armoury to provide weapons for the training. He originally asked for the then brand new MG4, but they sent him three crates of G8 and a few G36 with paint peeling off. 😀

    You should have demonstrated the “silent” (it is not so silent really, but more silent than normal) closing of the bolt. And if there was one avaiable you could have shown the linkless feedbox for HK21. Oh and the “HK slap” is an USian thing. Drill in the Bundeswehr is to just pull the locked back charging handle a little further back and down and then let loose.

    With that scope claw mount with the Trijicon VCOG on top it needs the Spuhr stock with an additional cheek riser. Could have brought your own from home, because trigger group and stock interchange with the G3. 😉

    • Jane’s Infantry Weapons used to list some HK11/HK21 variant for German special police forces which also could convert between the sniper and full-auto functions, with scope, magazine feed and bipod, and the extra-long receiver and I think a heavy precision barrel. There’s always been some part of Germany’s national police organized like an army and loaded for bear, presumably mass uprisings. You can find pictures of police panzers. A police firearm like this probably only needs to be somewhat accurate in the sniper mode because the ranges are so short, and the full-auto is for scenarios the government doesn’t want to admit exist.

  4. A promotional film produced by HK in the the early seventies showed the HK21 firing an entire 500 round belt in one single burst. Pity it did not find its way into youtube.

    Regarding slapping the charging handle, I do not buy the urban legend story. The Bundeswehr field manual on the G3 (ZDv 3/13) in clause 329 (of the 1978 edition) explicitly says “nicht schlagen” (do not slap). And there was a booklet on typical G3 handling damages (Handhabungs- und Pflegeschäden) showing a worn charging handle rest as the result of slapping.

    • The “HK slap” was first demonstrated to me by a sales rep flogging the HK54 (MP-5) in 1979. When I released the bolt by the approved Bundeswehr (G-3) method of pulling the handle back and down out of the detent notch gently and then letting go of it to let the bolt run forward, he looked at me strangely.

      Of course, I was used to M14s, on which there’s really no other way to release the bolt from the hold-open other than pulling back gently until the hold-open tab flips back under spring pressure, and then letting go of it.

      I blame Hollywood plus too much “macho” mentality generally, but that’s just a guess.



  5. Portugal did use the 7,62 mm MG3. His armed forces used both machine guns; the HK-21 (metralhadora ligeira 7,62 mm m/963 HK21) as a squad automatic weapon, and the MG-3 (metralhadora 7,62 mm m/962 MG42) as support weapon (platoon level, maybe). Both were purchased initially from Germany but later made in Braço de Prata Arsenal (near Lisbon).

  6. The G8 machine gun mentioned by Sommerbiwak got its funny designation as a rifle (Gewehr) due to political considerations. It was first adopted by German police at a time when it was fashionable to point out what a thoroughly civilian body the police was. Calling it a machine gun would have disturbed the illusions of the politicians.
    The same happened to the 40 mm Granatpistole, which the Police had to designate multi-purpose-pistol (Mehrzweckpistole).

    • One of the PR advantages of the G8 is that to politicians and(especially)journalists, it looks more like a rifle than an MG. And no, most of both wouldn’t understand the difference even if you explained it to them.

      Having been trained in “Police Community Relations” (a duty assignment I fortunately was never stuck with), I can assure you that LEO do consider such factors when buying equipment, even for tactical teams or CTW.



      • From point-of-view of Deutsch there is no problem, as MG or Maschinengewehr is kind of Gewehr (which means that every MG is Gewehr but not every Gewehr is MG). Rifle and MG do not work this way. Interestingly this situation is bit similar to U.S. cavalry using Combat Car in 1930s instead of Tank as second was considered infantry-only:

  7. As a belt feed can you attach a box/drum/can? Or is it loose belt only? When I was in the service (mid 90s) with the M-249 it was either a rattly plastic box or a belt, and I usually broke the belt into thirds, carried about 60-70 rounds on the gun, and ditched the boxes. Years later in A’Stan I became enamored with the quiet fabric ammo carriers.

  8. The Greek Army operates the HK11 which is the magazine-fed version of this gun, as its standard squad light machinegun (currently being replaced by the MINIMI in 5.56). Interestingly the Greek state manufacturer made under licence both the HK11 and the MG3. Thus the decision to buy HK11 had nothing to do with manufacturing. According to open sources the Greek Army bought some 20,000 HK11 and 12,000 MG3 in total in the 1980s and 1990s. The HK11 is issued at squad level while the MG3 is a company-level asset which typically gets distributed to platoons.
    I don’t know if this was a deliberate tactics-based decision or simply a 1 to 1 replacement of the BAR and the M1919.

  9. Xris,I was a conscript in the Greek Army,30 years ago and I remember both the G3 and the HK11.I think you are wright,it was a BAR replacement!I remember firing it in semi auto only,as full auto was reserved only for long term serving personel.I prefered it because of its milder recoil,due to its higher weight,and did not complain of carrying it all the way to the range-on foot of course.Its durability -as was the G3’s-was legendary ,as Ian says.

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