When you cycle the gun the bolt ... (I keep saying bolt), the barrel goes forward, like that. These were chambered in two different cartridges. They were made in 7.5x55mm Swiss and they were also made in the T65 cartridge, which was that, like, pre-NATO calibre. They saw absolutely no commercial success, very few were made. This is serial number 156, although I don't know if that is a total number of these that were produced, or if, I suspect, that is a sequential number from a bunch of different types of post-war experimental rifles. So, without further ado, let's go ahead and start digging into the mechanics on this because there's really no other history for me to tell you. They experimented with it, and it went nowhere. So let's dig in. Alright, we are going to start by taking out the magazine, because this is a huge magazine that kind of gets in the way for me to be able to show you the rest of the gun.
So this lever up here is actually the magazine release, and I have to pull it all the way down, like that, and then I can pull the magazine out. Now, let's take a look at this. So this started out life as an LMG 25 magazine. ... It should be 25 rounds I believe as a result. However, they had to seriously change up the design at the top in order to accommodate this thing's strange blow-forward or forward acting gas operating system. And (I'm gonna get this out of the way, so it doesn't try and keep focusing on it), basically what we ... need is to be able to have a cartridge go straight up from the magazine into the breech face. It doesn't push forward, it just goes straight up. Which means, well, at the same time you can't have rounds coming straight up out of the magazine when the magazine's out, or else all the ammo flies out of the mag and you have nothing. So they have these two feed lips that you can see here, that are going to hold the stack of cartridges in.
And then when you put this into the gun, when you lock the magazine in, these two feed lips get spread apart and they allow the cartridges to start cycling up one at a time. So when the closed that's going to hold the stack of cartridges in place, when the ... barrel opens, goes forward, it's gonna allow one cartridge to come up high enough that when the barrel cycles back, it locks over that cartridge into the chamber and is ready to fire. So, you can see there are two little square lugs on the side here. If we look inside the magazine well, when I close the magazine lever here, when I open that this opens up and you can put the mag in, and when I close it these two arms come back and what those are going to do is actually squeeze themselves in between the magazine body... In between the body here, and these two arms, so they're going to pry those arms out. These lugs are going to lock into the side of the receiver, right here, to hold the mag in place.
And when the feed lips are spread far enough apart the cartridges will pop out the top. So that's why this is a really stiff... you know that these levers are nice and easy to operate without a magazine, but when you put a magazine in (and by the way there is also a front lug here that locks this thing in to get it at the correct height), when we put this in right to that position, and then close the magazine lever, it's now really tight because it has to pry these two up away from the magazine body. By the way, the one major publication that talks about this gun, The World's Assault Rifles, says that this is a disassembly lever, which it very much is not, there is no disassembly lever. So let's move on to... Well, actually a couple markings I should show you. ... This is really the only marking on the gun, the only descriptive marking, 156.
That's the serial number. All right. Now we have a bit of a conundrum back here. We have two selector markings 'E' and 'M' and I'm not sure what those are supposed to stand for. I'm used to like 'E' and 'D', or 'S' and 'F', or 'E' and 'F'. Red usually means fire, white usually means safe. We also have the situation here of something that's fairly typical of Swiss firearms, namely you have this ring shaped cocking piece and so, in theory, that ought to be the safe position with it horizontal, but it'll fire there. Because you can also take this and rotate it 90 degrees, again, typically Swiss, but it'll fire there as well. So I'm not sure what... And all configurations of this will do that. So, I'm not sure exactly what the firing controls are supposed to be here. What I do know is, according to the literature, this has a cyclic rate in full-auto of 350 rounds per minute, which ... I do find plausible after taking it apart.
We'll get to that in, I promise, just a moment. But how exactly these are set up, I don't know. This has to be a select-fire gun, there's no way that a rifle like this would be full-auto only, but it clearly is capable of full-auto. So if you know, tell me down in the comments. Moving along, we have a rear sight marked out to 1,000 metres. This is, very curiously, very similar to actually the MAS-36 and the early MAS semi-auto rifle's rear sights, where you actually have to push down (it's an aperture sight back here), and you have to push down on this and then you can adjust this slider to whatever range you like, and then let the ... actual leaf up (so push that down, slide this). The French got rid of this on their rifles, because they found that when you were shooting, under recoil this would tend to bounce and the sight would shift. So they went to a different system where there's a locking button on this slider.
Why you have that French sort of influence on this guy? I don't know. Our charging handle is right here on the side. And, of course, despite the fact that I keep attempting to pull this backwards, you do in fact cycle it forwards. And when you do, the barrel extends out the front of the barrel jacket, and past the muzzle brake. Notice the two big oval slots in the barrel there, those are to line up with the muzzle brake. So you get some effect from the muzzle brake through that. I do also want to point out that on this rifle it should be re-cocking whenever you cycle the action, but it doesn't.
And whether that's related to my inability to figure out the safe and fire positions I don't know. But we'll document exactly what we have here, and that's what's going on. The muzzle brake is just three slots on either side. We have a fairly typically Swiss front sight, although it's not protected with wings, which is a little bit unusual. We have a bayonet lug on the bottom, sling swivel on the side of the barrel jacket, and then a sling bar in the back, along with a somewhat unusual style of butt-stock. That's in there to allow you to get a line of recoil a little bit more closely to direct into your shoulder, instead of having your face and your line of fire elevated up above the shoulder. So it's actually not that uncomfortable of a gun to handle, although it is a bit front heavy with all the weight of the jacket and such. OK, now we can get to disassembly. And we are going to start by removing the front cap on this barrel jacket. There's a little wire here, which sits in a detent, right there, on this front component.
Just that prevents it from rotating under recoil, but it's nice and easy to pop it loose to take it out. So this unscrews. There is a big spring behind this, so once we get it a little bit further out we will have to hold onto it carefully, lest it go flying across the room. There it is, it tried to go flying across the room. Alright, so we have a couple of different things going on out here. This is the part that was actually screwed into the front of the barrel jacket. This is our gas piston. This guy is one of two springs in this system.
This would be, we'll call this the gas piston spring as opposed to the barrel spring. So this, by the way, is reminiscent of the MG42, this is a two wire, yeah, that is a two wire coiled mainspring. Now, without that spring, this barrel assembly is free to reciprocate back and forth here. This is all going to come out the back of the action, so the next thing we need to do is take out this cocking piece section. This is a little bit fiddly to do. I don't have a manual for this, we just kind of figured it out by trial and error. So, we have a locking bar right here, and this will rotate through ... 90 degrees, what we need to do is actually get it in a position where it will come out. There we go. So that comes out, and then, as I'm pulling this back, it is actually linked to the barrel assembly by this. So, does this not look incredibly Swiss, or what? As I pull this out it's going to come to here, should be able to go a little bit farther... Quick intermission, we're gonna go ahead and take the charging handle off, because I think it's catching on the bolt.
So, what we do for that is lift up on this little lever, which is holding in a lug that holds this whole thing on. Then this handle can slide off the front. By the way, I forgot to mention it, this little button is your manual bolt hold-open. If you push the handle forward and then push this down, it'll lock the bolt open, which makes things like magazine changes a bit simpler. There we go, all right bolt handle is off. You can see the little lug, right there, that was holding it in place. Now I think... There we go. Now we can pull this the rest of the way out. So this is our whole cocking piece assembly. (Just a little bit of persuasion), that is the barrel assembly, our connecting bar, and let's call this the barrel spring. Now, before we go forward, I want to point out a couple things. Right down in here you can see that there's not really anything going on inside this, the ... barrel shroud here, except about halfway down.
You can see a black ring and that is a shelf, a step basically. And one of the springs is going to sit on that step, so it's important to remember that. Here you have the view down from the back. There's not a lot you can see here except on the bottom, right about there, you can see sort of a semi-circular crescent shape. That is one of the two locking recesses, and there's another one at the top that you can just sort of barely see there. But the top locking recess is ... inside this bulge at the front of the receiver. So the way this thing actually locks is with two flaps, right here. These are oriented vertically, when ... it's installed in the gun, and when this sliding piece goes backward it forces those two flaps to lift out, and those lock into those two recesses in the receiver, one in the top and one in the bottom. Looking at the face of the barrel here, we have, basically, just a big feed ramp and an open area to allow the breech face in.
This is our breech face and striker assembly, and it's fixed in the gun. So when I was taking it out, I'm basically taking these interrupted lugs and arranging for them to pop out the back of the receiver. The front here is our breech face. So think of this as the bolt, except on this gun, because it's a forward operating gun, the bolt stays where it is and the barrel moves. The magazine is going to fit right here into the bottom of the breech face. So when a cartridge feeds, it's going to go from the magazine and travel straight up into the extractor grooves right here. After you fire, it's going to ... be ejected out this side of the gun, and in order to allow that to happen we have a removable chunk of the ... rim engagement, so you can see that that's got a little hook in it, a little cut in it, and that engages the rim and holds the cartridge in place when you're firing.
Once you're done firing, when the barrel starts to go forward, this is going to be lifted off, which allows the cartridge to tip out towards the camera. You can see that there's a little cutout here that allows it to lift completely out of the breech face and eject. In full-auto it's fired by this trip right here. When this goes down it releases the striker, it expands that spring and it comes up through the breech face right there and fires. This, right here is, of course, directly connected to the ring handle. So when I pull that back you can see I've re-cocked the action like that. Dropping this guy, drops it forward and it fires. OK, so here's the most complicated part of the whole thing. And bear with me I'm ... gonna do my best to explain this. We have two springs, we have gas ports in the barrel here. When this is assembled, you've got this gas piston spring sitting over the top of this barrel spring.
You remember how at the beginning I pointed out a shelf inside the barrel sleeve? Well, that shelf is what this spring rests on. So when this is assembled, this gas piston spring is acting against a fixed surface here in the barrel shroud. The piston itself is going to sit right up against this ring, which allows it to compress the ... inner barrel spring. So, when you fire, you have your gas ports ...
Right here, which are going to vent gas into a chamber area in between this (which is threaded into the very front of the barrel shroud), and this gas piston. So it's it's gonna fill this area with gas, which is going to force the gas piston back. The barrel cannot move at this point because it's locked in place into the receiver. So, what's going to happen is this piston is going to reciprocate all the way back to here, and it's going to lock onto the front of the barrel over piece, thing. We'll call this the 'thing' inside there. The gas piston locks onto the 'thing', once this happens, we've compressed the outer spring as well, and....
Locked together now, this is all one component. And so as soon as this locks backwards, gas pressure dissipates out, and then this spring is going to push this whole assembly forward. And that is what actually pulls the chamber off of the cartridge. So the cartridge is going to be sitting in the breech face (actually, we've got our breech face right here), the cartridge is going to be sitting in the front of this breech face, static. The barrel, under spring pressure, is now going to move forward like this. So there's a bit of a delay here, and that's what contributes to the low rate of fire. This piston has to compress back first. This actually has shades of the Farquhar-Hill and the Beardmore-Farquhar British guns to it, sort of, not quite identical, but elements of that.
So this is going to go forward, and it's going to go forward until... So it's here, and it's going to move forward like this, until this piece actually ... until this slides up over this muzzle brake section, because when this goes all the way in it's going to trip this spring and unlock it, plink, like that. At that point remember, this is threaded into the front of the barrel shroud and static in place. So once we ... release this inner spring, it's going to push the barrel backwards like that, which pushes the chamber back over the next cartridge coming up out of the magazine, it re-cocks the striker in theory, but that piece appears to be missing here.
And then you're ready to fire another shot. What I didn't show you before that will make this clear. The way that this latching and unlatching works is that we actually have this compression (I don't even know what off the top of my head because I'm a little bit befuddled from trying to figure out this whole thing). I can't remember what the technical name for this is, but the four prongs on this will compress. And that's exactly what the gas piston does. When it goes all the way in, it's actually going to latch over this, like that, and lock it in place. There's a little ridge right up in here that does it. And then this guy is going to push those four tongues back down, which unlocks them from this, and allows this spring to expand again. Now we also have this connecting rod to talk about. This is going to sit right in the side of the barrel assembly. So this is fixed to the barrel, and as the barrel goes back and forth, this does as well.
It has this little spring-loaded hook on it, and this is what actually cocks the action. So I think I had this mis- installed the first time, when you saw the outside of the gun, and we'll find out when I reassemble it after this whether it works properly. But the way this is supposed to work, this lug right here is connected directly to our striker. This hook, right here, hooks on to that shelf, right there. Which should then cock the striker when this piece moves backwards, because this whole block is fixed in the receiver. So that should make the whole thing work, and I suspect I previously had it installed with the hook like just in front of that catch surface, or or something like that. So, that I think is actually pretty much the whole gun here. I think that's most of what we need to talk about. So you have two sear surfaces. You've got one down here, and in semi-auto this is ... what fires the gun. ... The trigger drops this here, just like a submachine gun sear, which would be holding this back.
And then this is your out of battery safety as well as being your auto-sear. So, the striker will be ... re-cocked by this guy, and then when this drops it allows the striker to come forward (it's already in the forward position). So, alright, let's put this back together and see if that actually works now. Alright, there is the SIG AK-53 field stripped. We've left a couple components together. Like there's no way I'm going to take all the pins out of this. I definitely don't really want to get into disassembling that. This took several hours to figure out to this point, and I think we can pretty well understand how it works. So I'm going to now go ahead and reassemble it, and see if it actually ... speaking of which, see if it actually does properly work once I reassemble it the right way.
Alright, I have gotten it back together. However, despite my best efforts to make sure I had it exactly put together right, it still doesn't want to cock. So I don't know why at this point, and I am going to assume that either ... well, I don't have enough time here at the Armouries to take more time to try and figure that out. And to be honest, I don't remember if it actually cocked before I started taking it apart, so it wasn't something that I had noticed. So, ... the good news is I did get it back together. So, in the recovery period after finally getting this thing both disassembled and then reassembled, preparatory to putting it on camera here, I was trying to figure out, like, is this actually the most complex gun that I've ever disassembled.
And the answer is not quite. Because for all of its ludicrous weirdness, it actually comes apart with no tools. The trouble is understanding how it works, because once you understand it, it's actually not that complicated to take apart. It's just tricky to figure out, and there are other guns out there, like notably the British EM1 bullpup that even once you understand how it works, it's still kind of fairly tricky to actually take apart and put together. So this is definitely ... I think this is the only forward operating gas piston ... it's the only forward operating barrel moving gun that I'm aware of. So there are a couple other guns that do have forward moving pistons. The Saint Etienne 1907 machine guns do, but they have a fixed barrel and a gas piston that moves forward just so that a rack and pinion can push a bolt backward. This has a fixed breech block and the barrel actually cycles forward, sort of under the influence of a gas system. So I think I can safely call it a unique operating system. But once you understand it, not actually the most complicated thing ever.
At any rate, I would like to give a big thanks to the patrons out there, those of you who directly support Forgotten Weapons and it's you guys that make it possible for me to travel to find awesome, totally unique guns like this one and bring them to you. And, of course, I found this at the Pattern Room at the British Royal Armouries, and I'd like to give a big thanks to them as well for giving me access to come in and figure out how to tear this thing down and show it to you guys. So their collection is not open generally to the public, but it is available by appointment to serious researchers. So if that describes you, take a look at their link to their catalogue below. You can, everyone in fact can, check out all of the different stuff they have in the collection. And if you'd like to make an appointment to come take a look at something for your own research, ring them up and they'll work with you. Thanks for watching. .
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Posted from my blog with SteemPress : http://riflings.com/2019/03/20/sig-ak-53-a-truly-weird-forward-operating-rifle/