Hi guys, thanks for tuning in to another
video on ForgottenWeapons.com. I'm Ian McCollum, I'm here today at Marstar up in Canada, taking a look at their Yugoslav M84 copy of the Soviet PKM. And this is the best belt-fed general
purpose machine gun I can think of. Now after World War Two the Soviet
Union kind of went through a period of developing a whole new batch of weapons. Now
of course everyone kind of did this after the war. World War Two was ... basically the end of bolt actions,
and the Cold War would see a whole new generation of small arms developed. The Soviets were no
exception, so of course they developed the AK to replace their submachine guns. They
developed the SKS to replace the Tokarev rifles, then realised that the SKS was kind of superfluous
in light of the AK, so they dropped the SKS. And then the Soviets had a bunch of machine
guns lying around that needed to be updated. So they had Goryunov 1943 guns, they had Maxim
guns, and they had seen, like several other things, they had seen the effectiveness of the
German military's universal machine gun concept, the general purpose machine gun. Which
in German service was the MG34 and the MG42. These guns were developed to be hopefully
light enough for a single man to carry and fire (and the MG42 is just barely within that category). But the guns had integral bipods, they could be fired off the bipod
typically by a two-man team of a gunner and an assistant gunner, or they could be mounted on a very effective tripod and used
as emplaced guns for delivering very accurate long range fire. Set these things up in defensive positions and they'd
be just as good as something like a Maxim gun really. Or you could run around with them carried,
advance with infantry, that sort of thing. This was the universal machine gun, and the
Soviets decided that they wanted in on that concept. So in the 1950s they put through a development
program for a new universal light machine gun. This was developed by a guy named ... Nikitin and a
General Sokolov, now Sokolov's name you may recognise, he was also the guy who developed the
wheeled mount for the Maxim and SG-43 guns. But this Nikitin-Sokolov gun was
doing pretty well, people were liking it. ... I think they built 500
pre-production trials models, it did well. And then, ... because of some internal politics,
the details of which are still really not clear to this day, someone decided that they'd really like to see a
competitive gun to that developed by the Kalashnikov team. So Kalashnikov was just finishing up his work
on the AKM, turning that from a milled gun into a stamped receiver gun, or back into a stamped
receiver gun that could be effectively produced, and at this point by the way this
isn't just Mikhail Kalashnikov, this is Kalashnikov and a whole
supporting team of engineers. And Kalashnikov's team puts a few guys
on the job and in relatively short order they come up with their version of the universal
machine gun, which is the PK, Pulemyot Kalashnikov. And in a bit of an upset, the Kalashnikov gun is the
one that's formally adopted by the Soviet military. It's adopted in 1961, goes into production.
In 1969 they updated it in a few fairly minor ways it became the PKM, or modernised, in '69. The visible changes were some strengthening
ribs added to the top cover, the original PKs had a finned barrel for better heat radiation,
and they realised that wasn't really all that effective or important, so they got rid of it, replaced
it with just a smooth barrel with a better style of flash hider, that's the most
distinctive way to recognize a PKM. And these guns are still in massively widespread
use today, as everyone who's watching this video probably recognises. They've been
manufactured by a number of other countries, Iran, China, Poland, Yugoslavia here, Serbia now. I'm sure a couple others that I'm leaving out. But they are an excellent, excellent balance of
all of the characteristics that go into gun design. So you always ... need reliability, you need
durability, you need weight, you need recoil control, you need rate of fire. ... Every aspect of this can
be maximised in a gun, but everything is a trade-off. If you really, really maximise the weight by having a
very, very lightweight gun, that's great to carry around, but then you're always going to have a downside
with your parts won't be as durable, the recoil will be much heavier, it may not be as controllable.
All of these things are compromises in gun design. And Kalashnikov's team
did an outstanding job balancing all of these different
elements when they came up with the PK. Alright, where to start?
This is an open bolt firing machine gun. It is chambered for the 7.62x54 rimmed cartridge
that was the standard Russian machine gun cartridge at the time, and it does in fact use the same
belt that the Russian machine guns have all used, going right back to the Maxim Gun. It's an excellent belt,
it works well in 54 rimmed, no reason to get rid of it. This is a pull out style of belt, ... well, we'll
get to that when we open up the action. ... They have 100, 200 and 250 round belts
and we have this box on the bottom of the gun. This box is there for infantry dismounted use of the
gun, so that you don't have to unload it before moving. It is clamped to a bracket here underneath
the gun, in fact, we can use this tab right here to pull it off the gun. You would
load this up by opening it up here, there's the inside, belt goes in there, 100
rounds, close it, latch it so it doesn't come open, and then you can open up this side. You have a
nice round surface to feed cartridges up and over and here into the gun. There is a scope mount rail on here as well, and the Yugoslav
military produced a 5x power optical sight to go with this. Snaps right on there. However you ... don't see those
used all that often. This is a gun that really kind of works just fine with its iron
sights, so we'll take this off for the time being. The sights are very similar to those of the RPK. Or AK. In fact there are a lot of elements on
this gun that are very similar to the AK, which makes sense because it
was designed by the same group. The only real difference is that the
leaf goes that way, instead of that way. But this is a windage adjustable leaf, you
have an adjustable dial right there like the RPK, and then you can set it to various different
ranges from 100 out to 1,500 metres. Front sight is also very reminiscent of the AK.
It's just a threaded in, round, flat top post. Protective wings. The whole front sight
block actually is very much like an AK. And we have a big chunky flash hider out there. The barrel is detachable but it's not
quite as quick as some other designs. So normally on most guns you'd have
some sort of external lever to unlock the barrel. On the PK and PKM you actually have to
open the top cover and then lift up the feed tray, and then we have a block right in here,
and that's what locks the barrel in. It's a little difficult to get a good angle
on this, but what we're going to do is I just have to push that back, and then
this block can be pushed laterally out the side of the gun. It's captive,
so it's not coming off there. And what this does is actually locks
a guide rib on the barrel into the gun. ... This slides over that rib on the
barrel, and that's what locks it in place. So I pull that out, it's captive there,
and then I can pull the barrel off. Now the trickiest bit of removing the barrel
on a machine gun is typically that first little bit, getting it unstuck where it's inevitably kind
of carboned into the gun from a lot of firing. Well, that's been addressed here as well.
This carry handle pivots on this screw and it actually cams the barrel away from
the receiver for you when you lift the handle up. So that gives you a really good bit of
initial leverage to unstick the barrel, and once you've got it that far,
then it's easy to just pull out. So there's our removed barrel,
we have the gas system there which is adjustable should it need to be,
but I don't think it typically needs to be. And the rear breech end. Now further disassembling the PK is a little bit
unorthodox. Again, with a typical machine gun you would usually have some way to remove
the stock, and then the recoil spring comes out and all the guts come out the back of the gun. The PK does not have that, instead the
buttstock is firmly ... screwed in place. But you have a rear trunnion that's riveted in
place here, kind of like an AK rear trunnion is. So you're not pulling the back of the gun off. Instead what we're gonna do is pull the recoil spring out. ... There's a lot of recoil spring in here,
so it's a little stiff but we pull that up and it actually has a pivot, a joint, in the guide
rod here, so when you're actually using the gun that guide rod is straight, but when
it comes to disassembly it can bend so that you can pull the recoil spring out. This is just a heavy fibre buffer to absorb the last
bit of impact of the bolt when it reaches end of travel. Once we have the recoil guide out then we can pull
the bolt and gas piston back. That comes to here and then that just pulls straight out of the gun as well. You'll notice the
gas piston attachment is similarly pivoted so that it can be removed,
just like the guide rod. And that's it, that's a field-stripped PKM. That's
as far as you have to tear it down for normal use. Now let's take a look at the working
bit here, the bolt and the bolt carrier. What's very interesting about this gun is
it's basically an up-scaled, oversized AK. So here we have an AK bolt, carrier and piston. And (if I can take this apart),
here is a PK bolt, carrier and piston. And they're really, really quite similar with the
exception of the PK being set up for belt feed. So AK bolt here on the right, PK bolt here on the left. The PK bolt is obviously a larger breech face
because it's using, well, a larger diameter cartridge, but you can clearly see that the locking lug
design, the extractor design, all of that's the same. And they both have this sort of bolt head and stem.
Now where they differ is in the firing pins. The AK is a hammer fired gun, so we have
a firing pin that runs the length of the bolt, and it gets hit by a hammer and
pops out and fires the cartridge. The PK is not a hammer fired gun.
There's no hammer mechanism. It has a very simple firing sear that just
drops down when you pull the trigger. In fact you can see it right there.
When I pull the trigger, sear drops. That's ... actually that's pretty similar to
the Degtyaryov, the DP-28, or DPM, but really simple, and no hammer to be seen. However, the PK does not have a fixed firing pin,
it still has a firing pin that floats here in the bolt. That firing pin has this one section, right there - shiny now,
that sticks out wider than the diameter of the bolt stem. The way that works is that there
is a groove inside the rear lug here, you can kind of see it right up in there. That groove retains the firing pin and controls it. So when I put the bolt in, I have to install it that direction. So there's the gun out of battery, and as the op rod goes forward, the bolt is going
to rotate, the locking lugs are going to engage, and then the ... op rod is going to go that last
bit forward which is going to push the firing pin through the breech face, fire the gun.
That's because this is an open bolt gun, so as soon as it's fully closed and locked it will fire, then under recoil the gas piston gets pushed
backwards, so that is going to come back. We have this interesting first bit of
travel here, where the bolt is still locked and the op rod is simply going
backwards leaving the bolt in place. That is called dwell time, that is going to
allow pressure in the chamber to drop, which is going to reduce the difficulty of
extraction among other things that it does. Then ... a rotating lug is going to
hit this cam surface in the bolt carrier. That's going to cause the bolt to rotate, to unlock, and then at this point it starts to
... extract the case out and then eject it. So you might be wondering what this
goofy looking claw thing is up on top. That is actually the mechanism
for pulling cartridges out of the belt. What happens is when this goes
all the way forward into battery, these snap over the rim of
the next cartridge in the belt, just like that. That seems like a pretty crude and simplistic system,
and it sort of is, but you know what? It works really well. ... Degtyaryov used this system, the ... RP-46, the belt-
fed version of the DP, used this same sort of system, and it just works. You have to temper these two arms correctly so
that they have spring tension to them and they don't snap off or get deformed. And in
fact if we look closely, I saw it before, yes, right there you can see those two little punch marks. Those are hardness testing. And you can see that
this whole claw assembly is dovetailed into the top of the rest of this bolt carrier assembly right there. So this is made differently with, I'm sure, a
different steel, different temper, different heat treat, because it needs to behave differently. And then
it gets added in right there, and you're ready to go. Speaking of belts, this is a Russian PK belt. Also works in the SG-43, the Goryunov,
also works in the Russian Maxim guns. It is complete on the top, and it is sort of skeletonised
on the bottom, and cartridges simply go in (they have loading tools to make that simpler), but cartridges go in just like that. This is a pull style of belt mechanism, meaning that those claws are going to grab the rim of the cartridge, pull the cartridge backwards out of the
case [belt] and then feed it into the gun. The alternative is a push through style of belt where
the cartridge gets shoved all the way through the link, but that doesn't work with this belt, obviously,
because we have a little small ring at the neck and because we have this big rim on the cartridge that
makes that sort of push through operation pretty difficult. If we look at the receiver of the gun, we
can see some more AK style similarities. The top cover design obviously is very similar to
that of the AK, in fact you'll notice the release button, right here, is actually basically patterned after the recoil
spring release mechanism on the AK pattern rifles. The receiver itself is a stamping, it's a relatively
simple stamping but it has to be done to a fairly precise set of tolerances and then there is a trunnion
riveted in the back and a trunnion riveted in the front, very similar to the AKM, which Kalashnikov's
team was basically putting the finishing touches on at the same time
they started working on this gun. Now what the AK doesn't so much have
are the extra added bits on the outside, so there's a reinforcing plate that's spot
welded on for the charging handle here. This is our attachment bracket for the
belt box, that gets riveted on the bottom. The trigger guard's riveted on, as with the AK. On this side we do actually
have an optics rail on this gun, and then we have an ejection port
right here, so that's kind of clever. In fact, I can show you that from here
before we put the gun back together. That ejection port cover is tensioned by this little coil
spring here, just like the dust cover on your AR-15. However, we have this piece of metal in
the receiver that's just on a pin back here, and when the bolt comes back,
the bolt pushes it out to the side, which causes it to push the ejection port
cover open. So as long as the bolt is in the ... in the middle position when it's actually going to be
ejecting a case, the ejection cover is automatically opened. When the bolt's not in that position the
ejection cover's automatically closed. So this is a system that works automatically,
you don't have to worry about whether or not you remembered to close it or remembered
to open it. It's just there doing its job. We have the same thing with the dust cover over the
feed port. It's spring-loaded so when you have the gun loaded, when you have a belt in there, this just kind
of sits down under spring tension on top of the belt. Because it's rounded here it's not
going to interfere with the belt feeding, but at any time, as soon as there's
no longer ammo in the gun, that snaps shut and keeps debris out of the action
without you having to remember to put it there. And to complete this system with the
last opening in the gun, the charging handle has a little sheet metal cover that travels with it.
So no matter what position the charging handle's in, you don't have an open gap
going all the way into the gun. That's not quite perfect, it's not hermetically sealed,
but it's pretty good and it's also very simple. One thing I realised I forgot to
mention earlier, control on the gun: the safety is here, there's no
semi-auto, this is full-auto or nothing. Forward is full-auto, rear is safe. So with the gun back assembled I can show
you a couple other elements of operation here. We have our feed pawl, which is
actuated by the operating rod down in here. So when the bolt comes back and forth
that feed pawl is going to cycle in and out, it's then spring-loaded, so in this position it catches a
round, it pushes it into the gun, and then on its way back ... it's pushed down, snaps under the next
cartridge and then comes up ready to feed again. This is where the belt is actually sitting, so in
the feeding position you would have a cartridge we can see it right there. And then you can also see operation
of the ejection port cover here. So when the bolt is in the ejecting position, it's open, at the very end of travel the port snaps shut so
that you can carry the gun cocked and ready to fire. with the port still closed. When the bolt comes
forward it opens, it doesn't really necessarily need to, but that's just kind of the by-product of ... the rather simple and effective way that
they have for keeping it open it open and shut. That should give you a pretty good
idea of the mechanics inside the PKM. So now I think it's time to go out and shoot this thing. I am really looking forward to that because
I really like shooting these things, so we will have the full shooting video
tomorrow, stick around and stay tuned for that. In the meantime, a big thank you to
Marstar for letting me play with their PKM. If you're up here in Canada, definitely check them out for
all of your ammo, gun, shooting supply sorts of needs. And a big thank you as well to my supporters on
Patreon. It's you guys who make it possible with dollar a month donations, or more
if you like the perks that are offered. But those donations make it possible for me
to travel around, come to places like Canada, and bring you guys guns like this one. Thanks for watching.
They also did the Kk 62, which apparently is a really weird MG.
And here he is shooting the M84.
Figured that this would be tangentially related to Wargame.