H&K’s Other 4.6: The 4.6x36mm HK36

hk36mag

Hognose tackles one of the most confusingly designated of all Heckler and Koch weapons, the HK36 (distinct from the G36) and its 4.6x36mm round (itself distinct from H&K’s 4.6x30mm PDW round):

Around 1970, Heckler & Koch was doing well, but their restless engineers were thinking: what’s next? One thing we learn from history is that no weapons system lasts forever, and there was maybe one more go-around in the company’s present line of roller-locked weapons, trading some militaries’ 7.62 NATO weapons for 5.56 NATO ones. But what could offer stingy weapons procurers enough reason to stop sitting on their wallets?

HK 4.6 x 36mm, made 1971. For sale here. It seems likely that there was only one lot.

The company explored many ideas, in two major strains. One is now well-known: caseless ammunition with a radically new action and new modes of fire, which became the G11 through many, many series of tests and evaluations in the 1970s and 1980s. The second was, perhaps, meant as a technical backstop if the G11, a technical stretch, proved infeasible. It became the HK36 — not the G36, the technical backstop HK had to create after the G11 failed, but the very obscure G36. The rifle existed in, perhaps, three prototypes. It used a unique 4.6 x 36mm intermediate cartridge.

HK 36 factory photo, as published in Full Circle.

The Big Ideas: Weight and Spoonery

When we referred to this as the “other” 4.6, we’re referring, of course, to the fact that this is not 4.6 x 30 HK round used in the familiar (at least, in appearance) MP7 series widely used by US and foreign special operations forces. The 4.6 x 30 is the latest of HK’s many attempts to make an even smaller caliber round, but it was aimed at a different objective: the short-range SOF and LE submachine gun, making most shots inside 100 meters; it has very light bullets (31-40 grains for warshots) and is a hair over half the weight of 9×19 or 5.56×25 ammo, allowing a reduction in operator burden (or an increase in ammo load, naturally).

The 4.6 x 36 was developed in the 1960s to meet a different requirement entirely: that of a normal assault rifle intermediate cartridge, with engagement ranges mostly inside300 meters. Two ideas drove the 4.6 x 36: reducing ammunition and system weight for a given effect, arguably the longest-standing trend in firearms design, and increasing terminal effect in the intended target, to wit, enemy homo sapiens. The first objective drove the reduction in caliber and length. To get to acceptable lethality, higher chamber pressures (51,200 psi CUP) were accepted, but the light projectiles (42 grain hard core/54 grain softcore) didn’t reach outlandish velocities (2,600-2,800 fps). It required a fast barrel twist to stabilize the light projectiles; 1 turn in 6.3″ was selected. HK claimed the round shot flat, allowing it to print to point of aim from 0 to 300 meters without any need for range compensation by the shooter or the sight.

The “spoonery” of the subtitle refers to an invention of Dr Gunther Voss of CETME, which remained in symbiosis with HK itself at least at the time he applied for German and US patents in 1964 and 65 (his US Patent, 3,357,357, was granted in 1967).

Voss Loffelspitz US3357357-0

“…to provide a rifle bullet wherein the tip of the bullet is of an asymmetric shape. When this bullet strikes the target, forces are generated which accelerate the bulet inclination.

It is stil another object of the present invention to provide a rifle bullet wherein the turning moment produced by the inclination accelerating forces increases and the bullet inclination is produced more rapidly when the distance between the bullet center of gravity and the bullet tip is greater. It is possible to increase the effect produced by the bullet tip asymmetry through the backward displacement of the bullet center of gravity.”

As Hognose himself would say, please do click through and Read The Whole Thing ™.

The HK36 is a truly weird firearm, with some prototypes representing the last en-bloc clip developments ever (the green plastic 25-round en-bloc of one being just visible in the title image). These were loaded through a door in the rifle’s fixed magazine body, after the follower was pulled down into the ready position by a lever connected to the follower via a chain:

HK36b

The HK36 with the loading lever retracted, and an en-bloc clip inserted. Image source: Weaponsman.com

 

By the time the HK36 was designed, the Germans were no strangers to micro-caliber rounds. Before the 21st Century, there had been no less than seven German micro-caliber experiments; the seven known to me being in chronological order the 4.15×45 RFA, the 4.7×45 DAG, the 4.9×45 DAG, the 4.3×45 DAG, the 4×37 IWK, the 4.6×36 CETME/HK, and the 4.6×30 H&K PDW, which barely squeaks in the door with an introduction date of 1999. What made the 4.6×36 different was that, as the name indicates, it was a joint effort between the governmental bureau CETME of Spain and H&K of Germany. As a result, rounds are seen with either red or green primer sealant, the former indicating Spanish manufacture and the latter indicating German manufacture. This development began with the Spanish 4×27 CETME round, which was designed to minimize ammunition weight while maintaining “humanitarian” wounding characteristics – a design criterion that sounds downright funny to the post-Madrid world.

The micro-caliber concept eventually died with the end of the Cold War, but was resurrected as a result of the NATO PDW trials, which in typical Treaty Organization fashion produced no standard round. Today, rounds with caliber smaller than .22″ are decidedly unfashionable where standard infantry rifles are concerned, but the potential benefits of a smaller caliber – retention of ballistic characteristics and a dramatic reduction in weight – remain.



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Riot

    “not the G36……but the very obscure G36.” – I think even the author got mixed up!

  • Sianmink

    That en-bloc magazine is truly bizarre. What were they thinking? I expect to see that from some piece of weird ephemera designed in the 1910’s and engineered to avoid infringing Browning patents, not from something designed in 1970.

    • Jake Barnes

      Cheaper to produce maybe?
      This could have been before the era of disposable magazines.

      • RocketScientist

        Article states cartridge was developed in 60’s. Assuming rifle was developed at approximately same timeframe, I think disposable mags were already very much accepted practice. No idea what they were going for with that weird chain-operated trap door en bloc clip arrangement. Positively Rube Goldbergian

        • You still had a lot of theorists worried about the weight of multiple spare magazines. In addition, there were folks who were worried about the durability of magazine tubes and springs when the magazines were left loaded for prolonged periods.

    • They were just following the typical German mechanical engineer’s philosophy: anything that can be made well with five parts can be made equally well with 22.

      • wetcorps

        And some rollers.

    • mosinman

      the more failure points and complexities the better it is !

    • Southpaw89

      Militarily it is obviously a flop, but maybe someone look into it as a solution for gun owners in states where removable mags are the source of all that is evil and wrong with this world, might beat a bullet button.

      • noob

        hmm make it for the ar15 and you might have a winner there

        • MR

          Check SHOT show coverage from a couple years ago, somebody did just that. IIRC, you pull down a tab on the baseplate, and pass the rounds through a “bullet shaped” port on the side of the mag/magwell.

          • iksnilol

            Yeah, but that doesn’t allow you to use an en-bloc clip.

            That is still only loading one round at a time.

          • MR

            The relevant authorities in those jurisdictions would probably consider the en-bloc clip to be analogous to a detachable magazine, and therefore verboten.

          • iksnilol

            Has anybody checked that? I mean, is a M1 Garand verboten in places like California with detachable magazine bans?

            Something like a featureless AR or Mini-14 with a fixed magazine and stripper clip guide might sell in those areas. Kinda like a western SKS.

          • MR

            Again IIRC, somebody suggested putting a stripper clip guide on the design I mentioned, I’m not sure if anything came of that. Good question on the Garand in California. The problem is, I’m trying to use logic, and that’s not how the legislative process works. You’d have to contact California DOJ and get a determination letter, much like dealing with the BATFE. Or maybe a Californian can chime in with current policy.

    • DW

      Maybe, just maybe, that they thought:
      1. Plastic body-ed magazine containing follower, spring would not be strong enough to hold together when full, or that feed lips would be too fragile
      2. You save weight by having the only complete magazine system “in the gun”- ie: You carry a Rifle and 6 “magazines” minus 5 follower/spring/yadayada
      But really, 1977 came the AUG and proved plastic mags are stronk enough for military use, and lol dat weight “savings”

    • John Daniels

      The point was so that the end users (soldiers) wouldn’t have to handle individual rounds. The thinking at the time was the it would be best if soldiers received their ammunition in ready-to-use packets that were prepared at the factory, and all they had to do was insert it into the rifle. Less room for grunts to screw things up at the last moment.

      • Sianmink

        You can do that with pre-loaded disposable magazines though, and leave out the levers and chains.

        • John Daniels

          Yeah. That’s part of the reason the concept was found unnecessary.

  • Brody

    I think Hk should make a modern version of this but with 4.6×30 and mp7 mags, semi auto. For you know, squirrels.

    • DW

      P90 best_squirrelgun_NA
      no? urgh.

      • iksnilol

        I would have loved the P90 if they made it in 9×19 or 7.62×25.

        As it is now, the ammo is simply too rare and expensive to be practical for me.

  • TheSmellofNapalm

    Was this before the notion of cheekwelds?

    • LCON

      was meant to be fired upside down

      • DW

        and bullet loaded backwards

  • Sulaco

    Can’t remember was this the projected environment for the never finished HK caseless ammo rifle as well?

    • DaveP.

      No, that was the G11- totally different machine.

  • The book “Die G11 Story” indicates that the 4.3mm, 4.7mm, and 4.9mm DAG rounds were merely test beds for evaluating the projectiles under consideration for the HK G11 caseless rifle. My understanding is that the 4x27mm CETME was a 1970s-era PDW project, postdating the earlier 4.6x36mm. The 4x27mm CETME is often seen loaded with projectiles having multiple facets, which are described in a later patent from Gunther Voss.

    https://www.google.com/patents/US3949677

    You’ll note that the HK36 had features that were carried over to the HK50/G36 nearly a quarter century later. Besides the carry handle with integrated optics, it also has a swiveling charging handle for ambidextrous use.

    The HK36 design included the following patents:

    https://www.google.com/patents/US3731417
    https://www.google.com/patents/US3736686
    https://www.google.com/patents/US3748959
    https://www.google.com/patents/US3774498
    https://www.google.com/patents/US3777381

  • hikerguy

    I can see some elements of what would be carried over to their current rifle, yet still see a little G3 in it as well.

  • Eric B.

    HA! I’ll still take my FN PS90 with its “5/7” cartridge over any HK 4.6 round and weapon. AND I have 50 round mags.
    I also bought two double mag pouches in Multicam from The Vest Guy. Great American craftsmanship in these mag pouches.
    With a Bushnell red dot sight my PS 90 is accurate (pie plate) offhand to 200 meters in my own testing.