Yugoslav M84 PKM: History, Mechanics, and Disassembly

 

The PK machine gun was developed by Mikhail Kalashnikov’s engineering team right about the time they were putting the finishing touches on the AKM. The PK is in many ways an AK rifle action enlarged, flipped upside-down, and mated with a belt feed mechanism. It uses the same belt design as the previous Soviet 7.62x54R machine guns (the Maxim, SG43, and RP46).

The PK was improved in a few relatively minor ways to become the PKM, and the Yugoslav military put it into production in 1984. The weapon is rugged, reliable, relatively lightweight, and arguably the best universal machine gun design ever produced.

Thanks to Marstar for letting me examine and shoot their M84!

 

53 Comments

  1. I agree that they are a superb balance of a weapon.I love the PK, even though the belt is a bit of a nuisance. I have used both Russian and Chinese PKs. The Chinese guns came with a batch of ak56 type 2s that are usually handed out as gifts by the Chinese Government. Even if they looked and smelt like PKs, they are complete rubbish. I have seen brand new guns worked hard (same treatment as dished out to other weapon types), parts will show deformation, chrome will start to flake off from the bore and the occasional bullet existing the barrel through the side of said barrel (cause barrels vibrating at an unsafe amplitude as they become dangerously soft due to improper material).

  2. This is probably smartest of all “sheet-metal” machine-guns. I still do have respect to both MG34 and MG42, however. If I remember correctly (with help of pictures 🙂 ) how vz.59 was built, it has completely different architecture; for one, receiver was machined out of billet, second – tilting link bolt locking and of course push-thru feed. Where hey have similarity is the source of belt advance being derived from operating rod via cam and tilt lever. This is also are of major variation with western guns (true, they are 2-stage while PK and vz.59 are single stage fed); it does not take anything away from reliability though. Oh yes and PK was in tank version, solenoid fired as well.

    What always gets me is to compare this rudimentary built receiver in comparison to what FN has settled for…. whooof. It takes longer to straighten after welding than to weld. Why? Mainly because FN guns have separate action guides which have to be attached to body, PK does not. They could have used for instance separate guide rod(s), why not?

    Good show and looking forward to more!

    • Main difference in that MAG receiver has to be machined since tilting bolt locking locks into receiver. On PKM bolt lock in the front trunion, so sides do not bear a full pressure of firing. Second, closed rear end gives a lot of structural integrity. Third pull-push feed is more reliable due the fact that removal of the cartridge happens when bolt is at the peak of the energy. All those were found out by US ordnance when they tested PKT in search of a MG to replace M73/M219. Here is on the Max Popenker’s blog:
      https://mpopenker.livejournal.com/2218571.html

      • Yes you are correct Bojan

        and I should have been more specific; what I had on mind was recent production of Minimi line guns, be it in 5.56 or 7.62 calibre. Their receivers are TIG welded out of stampings with exception of central trunion.

        Now, let me ask a question: how easy/ difficult was I your experience to clean gas compartment/ chamber on your machinegun? During my service we had to take shortcuts when cleaning vz.58. Occasionally door handles were missing since soldiers used them (euro-type door handles are of L-shape) together with patch of cloth to clean gas cylinder/ chamber. 🙂

      • Regarding 2-stage belt advance (MG42, MAG58) vs PK I do not see that much of disadvantage in single stage (e.i. pull at recoil) since it is natural to use the energy which is there. On action return, recoil spring has enough to do while feeding cartridge. I observed belt behaviour on various videos and it appears that its jittery movement is very similar but no more abrupt on PK. Perhaps Ian will take slow shot at this area.

      • Still on subject of feeding…. I can see some dis-advantage in western guns as they concentrate all of this working in complex (and expensive to make) feed cover area. In contrary, Russian guns in general put load where is the material (op-rod and swing arm, e.i. receiver) and minimize complexity of cover assembly while placing there only retaining fingers. I am not interested in bias, just trying for impartial observation from mechanical standpoint. If any bias should be applied, it would be against PKs rimmed cartridge. But, it appears that designers divided burden rather evenly – and successfully.

  3. Mg42 is very dangerous in defensive positions. Tripod, any army will have serious setbacks in advancing. Fire rate, is likely to hit, far more “targets” it was a devastating weapon, to advance towards. Less adaptable, but absolutely, completely lethal.

    • “Mg42 is very dangerous in defensive positions.”
      Anyway it should be fired in limited-length burst, according to:
      http://sovietguns.blogspot.com/2013/11/mg-42-guide.html
      Sustained aimed fire is not possible due to the high rate of fire and shaking of the gun. The dispersion cone moves away after 70 shots. Bursts longer than 70 rounds in length result in a waste of ammunition. Because of this, bursts should be limited to 70 shots, with rapid re-acquisition of the target afterwards

      • 70 quick is a lot. what it can do on an tripod, it can’t do on a bipod. But… A FNMag/Pkm is not an Mg42 on a Tripod, in direct fire mode, at least.

        • Yugoslavia adopted Pkm and Mg53 variant, Bojan your the (local) expert was an Mg53 “Lower rate of fire than Mg42 but still high” used mainly to complement Pkm on bipod or not? Ak- Ppsh, Sks argument Daweo.

          • “Yugoslavia adopted Pkm and Mg53 variant,”
            Shouldn’t be Zastava M53?
            If yes: M53 was done on original German machinery, I assume that it was either acquired for free or very low price. Additionally if 53 stands for “adopted in 1953” then it would be even before designing of PK started.
            If no: deliver correct designation

            What can I say? Excessive Rate-Of-Fire is excessive. Fact that some machine guns designed before and during WWII might be explained, by fact that back then AA role of machine gun was considered to be important. Not to grant designing special machine gun for that purpose, but enough to make some machine guns “2-speed” design like for example (ill-fated) DS-39: http://modernfirearms.net/machine/rus/ds-39-e.html
            Though rifle-caliber machine guns proved their effectiveness for low-altitude from First World War onwards, during World War II due to development in aviation technology (metal aeroplanes becomes standard, self-sealing fuel tanks, armor for defending vital parts) made rifle-caliber machine obsolete in this role. Big-bore (.50″ and similar) would retain usefulness some time longer, but anyway both would be replaced by ~20…~30 mm AA autocannons in this role. Nonetheless rifle-calibers machine guns were used for AA defense in the face of lack enough numbers of such autocannons, sometimes in multiple mounts (like for example Soviet quadruple Maxim mount).
            It is worth nothing that during WWII Germany has not own design for ground-usage heavy machine gun, for low-altitude AA defense 2 cm FlaK 30 was used, much heavier than heavy machine guns.

          • “No single weapon can achieve all things.”
            There are two contrary approach: universality and specialisation both applied too heavily (extreme universality or extreme specialisation) give rather unsuccessfully patterns, main question how much universality or specialisation is needed?

          • “I want to speak to the oganist not the monkey grinder.

            “It’s not tooling, they purposely decreased the rate””
            Now provide evidence, that altering design to change Rate-of-Fire mean that existing tooling can NOT be altered respectively.

      • Yugoslavia god documentation and some machinery for MG42 from Czechoslovakia in early 1948. Documentation for P-38 and G-43 were also acquired, and at a moment Tito split with Stalin documentation for StG-44 was to be acquired.
        Out of those, only MG42 saw production.
        P-38 copy in 7.62x25mm was a competitor to a modified TT (M57) and lost, G-43 was trialed as M52 rifle, but army was not satisfied with it fully, and even modifications to it (including reversal to external gas port/muzzle booster that apparently made it more reliable in dirty conditions) did not solve a problems with it. In the end, it was abandoned for a new plan, modified shortened Garand with 20 round mags in 7.92×57…
        StG, you know the story…
        Not everyone was happy with M53, it was judged to be too heavy for a LMG role and alternatives were sought (MAG was tested but was also too heavy, M60 was almost adopted)…
        Yugoslavia got license for PK series relatively late, in 1978 (IIRC, I could be off by a year or two), when it acquired production rights for T-72 tanks. PKM was immediately seen as a better LMG than M53 and was adopted in 1984. (as a designation says).

        • BTW, M53 production only started when new tools from US were acquired in 1952-53. Irony, MG42 copy being made on a mix of original and US made tooling… 🙂

          • I suspect that the U.S. tooling consisted mainly from materials/ technologies how to make it. I am not aware there was ever MG42 production in U.S.

          • Tooling from US were hydraulic presses, mills, lathes, barrel rifling machines ETC. Zastava was total wreck in 1945 and took until mid-50s to return to pre-ww2 number of machines.

  4. Backwards compatibility is also what lets Nintendo products play games from previous generation consoles from the same company, whether by accepting disks/cartridges or by virtual console memory. Competing consoles mostly failed to do the same, frustrating tons of players who wanted to see the classics without having to buy old consoles on auction.

    On the other hand, one generally does not reinvent the machine gun unless one can magically produce tooling and logistical support from nowhere.

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