At the end of January, 2018 and after many false starts, the Russian military formally announced the limited adoption of the AEK-971 and AEK-973 rifles. These rifles feature an unusual counterbalanced breech mechanism which is intended to improve handling, especially during full auto fire. While exotic outside of Russia, these counter-balanced rifles are not at all new. In fact, the 2018 adoption of the AEK-971 represents the first success of a rifle concept that has been around for a some time.
Animated diagram of the AK-107/108
Balanced action recoil systems (BARS) work by accelerating a mass in the opposite direction of the bolt carrier. The countermass is of similar mass to the bolt carrier and synchronized to move in the opposite direction by a rack and pinion. This cancels out some, but not all of the impulses associated with self-loading actions. But more on that later.
Long before Soviet small arms engineers began experimenting with BARS, a number of production weapons featured synchronized masses moving in opposite directions. Generally speaking, any stabilization that these actions provided was an incidental benefit. Rather, these designs were either attempts to get around patents, or very early developments in the history of autoloading weapons when the design best practices had not been standardized yet. These designs featured a forward-moving gas trap that, of necessity, needed its motion converted into rearward motion by either a lever or rack and pinion.
The French St. Etienne Machine Gun
The Danish Bang rifle
At around the same time, inventors started toying with the idea of using synchronized counter-masses deliberately to cancel out recoil impulses. The earliest patent for such a design comes from 1908 from obscure firearms designer Ludwig Mertens:
More information on these early developments is in this article on the matter by Max Popenker.
Soviet designers began investigating the BARS concept in earnest in the early 1970s. This is worth noting; these early BARS rifles were actually trialed against the AK-74.
The AL-7 rifle, a BARS rifle from the early 1970s
The Soviet military chose the more mechanically orthodox AK-74 as a stopgap measure in order to get a small-caliber, high-velocity rifle to the front lines as quickly as possible. Of course, the thing about stopgap weapons is that they always end up hanging around longer than intended, and forty four years later Russian troops are still equipped with the AK-74.
A small number of submachine gun prototypes with a BARS-like system were trialed, but not mass-produced. The gas operated action of a rifle can be balanced with a fairly small synchronizer rack and pinion, but the blowback action of a submachine gun requires a fairly large and massive synchronizer gear or lever. This is because in a gas operated rifle a second gas piston can be attached to the countermass, thereby unloading the synchronizer gear.
There are three BARS designs of note from Russia:
The AK-107 and AK-108 are BARS rifles in 5.45x39mm and 5.56x45mm respectively. These rifles are products of the Kalashnikov design bureau and Izmash factory, now Kalashnikov Concern. Internally they are very similar to an AK, only with the countermass and synchronizer unit situated above the bolt carrier group.
Close up of synchronizer and dual return spring assemblies
This is configuration is almost identical to the AL-7 design of the early 1970s. Like the more conventional AK-100 series, the AK-107/AK-108 were offered for export during the late 1990s and early 2000s, but they failed to attract any customers. The furniture is very similar to the AK-100 series, and indeed the only obvious external difference is the long tube protruding from the gas block and bridging the gap to the front sight.
The AK-107 has re-emerged recently as the Saiga 107, a rifle clearly intended for competitive shooting events like 3-gun.
The rival Kovrov design bureau was only slightly behind the Kalashnikov design bureau in exploring the BARS concept. Their earliest prototype featuring the system, the SA-006 (also transliterated as CA-006) also dates from the early 1970s.
Chief designer Sergey Koksharov refined this design into the AEK-971. The chief refinement of his design over the first-generation balanced action prototypes from the early 1970s is that the countermass sits inside the bolt carrier, rather than being stacked on top of it. This is a more compact installation of the mechanism, but otherwise accomplishes the same thing.
Moving parts group of the AEK-971
The early AEK-971 had a triangular metal buttstock and a Kalashnikov-style safety lever on the right side of the rifle.
In this guise the rifle competed unsuccessfully with Nikonov's AN-94 design in the Abakan competition. Considering that a relative handful of AN-94s were ever produced, this was perhaps not a terrible loss for the Kovrov design bureau.
After the end of the Soviet Union, the AEK-971 design was picked up by the Degtyarev factory, itself a division of the state-owned Rostec.
The Degtyarev factory would unsuccessfully try to make sales of the weapon for the next twenty four years. In the meantime, they made some small refinements to the rifle. The Kalashnikov-style safety lever was deleted and replaced with a thumb safety on the left side of the receiver.
Later on the Degtyarev factory caught HK fever, and a very HK-esque sliding metal stock was added in addition to a very HK-esque rear sight. The thumb safety lever was also made ambidextrous. The handguard was changed a few times.
Still, reception to the rifle was lukewarm. The 2018 announcement that the rifle would be procured in limited numbers alongside more conventional AK rifles is not exactly a coup. The numbers bought are likely to be very low. A 5.56mm AEK-972 and 7.62x39mm AEK-973 also exist. The newest version of the rifle has been referred to as A-545.
AKB and AKB-1
AKB, closeup of the receiver
The AKB and AKB-1 are a pair of painfully obscure designs designed by Viktor Kalashnikov, Mikhail Kalashnikov's son. The later AKB-1 is the more conservative of the two, while the AKB is quite wild.
Both rifles use a more or less conventional AK type bolt carrier, but the AKB uses the barrel as the countermass. That's right; the entire barrel shoots forward while the bolt carrier moves back! This unusual arrangement also allowed for an extremely high cyclic rate of fire; 2000RPM. Later on a burst limiter and rate of fire limiter were added. The rifle would fire at the full 2000 RPM for two round bursts, but a mere 1000 RPM for full auto.
The AKB-1 was a far more conventional design, but it still had a BARS. In this design the countermass was nested inside the main bolt carrier, similar to the AEK-971.
Not a great deal of information is available about these rifles, but @Hrachya H wrote an article on them which can be read here.
Here at Sturgeon's House, we do not shy from the wholesale slaughter of sacred cows. That is, of course, provided that they deserve to be slaughtered.
The discipline of Military Science has, perhaps unavoidably, created a number of "paper tigers," weapons that are theoretically attractive, but really fail to work in reality. War is a dangerous sort of activity, so most of the discussion of it must, perforce, remain theoretical. Theory and reality will at some point inevitably diverge, and this creates some heartaches for some people. Terminal, in some cases, such as all those American bomber crews who could never complete a tour of duty over Fortress Europe because the pre-war planners had been completely convinced that the defensive armament of the bombers would be sufficient to see them through.
In other cases though, the paper tiger is created post-facto, through the repetition of sloppy research without consulting the primary documents. One of the best examples of a paper tiger is the Tiger tank, a design which you would think was nearly invincible in combat from reading the modern hype of it, but in fact could be fairly easily seen off by 75mm armed Shermans, and occasionally killed by scout vehicles. Add to this chronic, never-solved reliability problems, outrageous production costs, and absurd maintenance demands (ten hours to change a single road wheel?), and you have a tank that really just wasn't very good.
And so it is time to set the record straight on another historical design whose legend has outgrown its actual merit, the British EM-2:
EM-2ology is a sadly under-developed field of study for gun nerds. There is no authoritative book on the history and design of this rifle. Yes, I am aware of the Collector's Grade book on the subject. I've actually read it and it isn't very good. It isn't very long, and it is quite poorly edited, among other sins devoting several pages to reproducing J.B.S. Haldane's essay On Being the Right Size in full. Why?!!?!!
On top of that, there's quite a bit of misinformation that gets repeated as gospel. Hopefully, this thread can serve as a collection point for proper scholarship on this interesting, but bad design.
Question One: Why do you say that the EM-2 was bad? Is it because you're an American, and you love trashing everything that comes out of Airstrip One? Why won't America love us? We gave you your language! PLEASE LOVE ME! I AM SO LONELY NOW THAT IT TOLD THE ENTIRE REST OF EUROPE TO FUCK OFF.
Answer: I'm saying the EM-2 was a bad design because it was a bad design. Same as British tanks, really. You lot design decent airplanes, but please leave the tanks, rifles and dentistry to the global superpower across the pond that owns you body and soul. Oh, and leave cars to the Japanese. To be honest, Americans can't do those right either.
No, I'm not going to launch into some stupid tirade about how all bullpup assault rifle designs are inherently a poor idea. I would agree with the statement that all such designs have so far been poorly executed, but frankly, very few assault rifles that aren't the AR-15 or AK are worth a damn, so that's hardly surprising. In fact, the length savings that a bullpup design provides are very attractive provided that the designer takes the ergonomic challenges into consideration (and this the EM-2 designers did, with some unique solutions).
Actually, there were two problems with the EM-2, and neither had anything to do with being a bullpup. The first problem is that it didn't fucking work, and the second problem is that there was absolutely no way the EM-2 could have been mass-produced without completely re-thinking the design.
See this test record for exhaustive documentation of the fact that the EM-2 did not work. Points of note:
-In less than ten thousand rounds the headspace of two of the EM-2s increased by .009 and .012 inches. That is an order of magnitude larger than what is usually considered safe tolerances for headspace.
-The EM-2 was less reliable than an M1 Garand. Note that, contrary to popular assertion, the EM-2 was not particularly reliable in dust. It was just less unreliable in dust than the other two designs, and that all three were less reliable than an M1 Garand.
-The EM-2 was shockingly inaccurate with the ammunition provided and shot 14 MOA at 100 yards. Seriously, look it up, that's what the test says. There are clapped-out AKs buried for years in the Laotian jungle that shoot better than that.
-The EM-2 had more parts breakages than any other rifle tested.
-The EM-2 had more parts than any other rifle tested.
-The fact that the EM-2 had a high bolt carrier velocity and problems with light primer strikes in full auto suggests it was suffering from bolt carrier bounce.
As for the gun being completely un-suited to mass production, watch this video:
Question Two: But the EM-2 could have been developed into a good weapon system if the meanie-head Yanks hadn't insisted on the 7.62x51mm cartridge, which was too large and powerful for the EM-2 to handle!
Anyone who repeats this one is ignorant of how bolt thrust works, and has done zero research on the EM-2. In other words, anyone who says this is stupid and should feel bad for being stupid. The maximum force exerted on the bolt of a firearm is the peak pressure multiplied by the interior area of the cartridge case. You know, like you'd expect given the dimensional identities of force, area and pressure, if you were the sort of person who could do basic dimensional analysis, i.e. not a stupid one.
Later version of the British 7mm cartridge had the same case head diameter as the 7.62x51mm NATO, so converting the design to fire the larger ammunition was not only possible but was actually done. In fact, most the EM-2s made were in 7.62x51mm. It was even possible to chamber the EM-2 in .30-06.
I'm not going to say that this was because the basic action was strong enough to handle the 7x43mm, and therefore also strong enough to handle the 7.62x51mm NATO, because the headspace problems encountered in the 1950 test show that it really wasn't up to snuff with the weaker ammunition. But I think it's fair to say that the EM-2 was roughly equally as capable of bashing itself to pieces in 7mm, 7.62 NATO or .30-06 flavor.
Question Three: You're being mean and intentionally provocative. Didn't you say that there were some good things about the design?
I did imply that there were some good aspects of the design, but I was lying. Actually, there's only one good idea in the entire design. But it's a really good idea, and I'm actually surprised that nobody has copied it.
If you look at the patent, you can see that the magazine catch is extremely complicated. However, per the US Army test report the magazine and magazine catch design were robust and reliable.
What makes the EM-2 special is how the bolt behaves during a reload. Like many rifles, the EM-2 has a tab on the magazine follower that pushes up the bolt catch in the receiver. This locks the bolt open after the last shot, which helps to inform the soldier that the rifle is empty. This part is nothing special; AR-15s, SKSs, FALs and many other rifles do this.
What is special is what happens when a fresh magazine is inserted. There is an additional lever in each magazine that is pushed by the magazine follower when the follower is in the top position of the magazine. This lever will trip the bolt catch of the rifle provided that the follower is not in the top position; i.e. if the magazine has any ammunition in it.
This means that the reload drill for an EM-2 is to fire the rifle until it is empty and the bolt locks back, then pull out the empty magazine, and put in a fresh one. That's it; no fussing with the charging handle, no hitting a bolt release. When the first magazine runs empty the bolt gets locked open, and as soon as a loaded one is inserted the bolt closes itself again. This is a very good solution to the problem of fast reloads in a bullpup (or any other firearm). It's so clever that I'm actually surprised that nobody has copied it.
Question Four: But what about the intermediate cartridge the EM-2 fired? Doesn't that represent a lost opportunity vis a vis the too powerful 7.62 NATO?
Sort of, but not really. The 7mm ammunition the EM-2 fired went through several iterations, becoming increasingly powerful. The earliest versions of the 7mm ammunition had similar ballistics to Soviet 7.62x39mm, while the last versions were only a hair less powerful than 7.62x51mm NATO.
As for the 7mm ammunition having some optimum balance between weight, recoil and trajectory, I'm skeptical. The bullets the 7mm cartridges used were not particularly aerodynamic, so while they enjoyed good sectional density and (in the earlier stages) moderate recoil, it's not like they were getting everything they could have out of the design.
note the flat base
In addition, the .280 ammunition was miserably inaccurate. Check the US rifle tests; the .280 chambered proto-FAL couldn't hit anything either.
56K unfriendliness follows:
Artistic 3D cutaway of the GSh-18 from Abiator
In the early 1990s, the Russian military began looking for a replacement for the long-serving Makarov PM pistol. The Makarov, while a sound and simple design, was an old-fashioned design that could not take advantage of the latest advances in polymer and ammunition technology. A certain Austrian businessman had shown that it was quite possible to make pistol frames out of injection-molded plastic instead of laboriously milling them out of steel or aluminum, and the world had well and truly taken note. In addition, powerful new armor-piercing ammunition had been developed in Russia that was too much for the simple action of the Makarov pistol to handle.
The 7N31 9x19mm round. The bullet consists of a steel penetrator wrapped in a lightweight jacket. The propellant burns at extremely high pressure for a 9x19 round and will wreck Glocks.
The two leading contenders were the GSh-18 and the PYA. Both designs used locked breech operation with very beefy locking geometry in both designs to handle the large bolt thrust of the new armor-piercing ammo. Additionally, both designs featured two-column magazines to give them much greater capacity than old PM (17 rounds for the PYA and 18 for the GSh-18). However, while the PYA used a hammer and a traditional metal frame, the GSh-18 was quite in line with the latest thinking in small arms design and used striker firing and a polymer frame.
The PYA pistol
In any event, the economic and political chaos of the 1990s permitted only limited replacement of the Makarov within the Russian military. The 1950's vintage PM is still a common sight with Russian soldiers.
A Russian soldier with a slung AK-74M reloads his Makarov pistol
The GSh-18, from Forgotten Weapons
The GSh-18's unusual aesthetics and excellent lineage earned it plenty of attention from weapons nerds in the West. Anyone familiar with Soviet aircraft armament knows the names Grayazev-Shipunov. Could this pistol be a diamond in the rough? A future champion, waiting to explode onto the world market? A Russian Glock?
Well, thanks to a set of pictures that LoooSeR posted from photographer and MVD operator KARDEN, we now know that the answer is NO.
The quality of construction of these pistols... leaves something to be desired. In fairness, some of the roughness is because this particular specimen has been hit with a file to de-fang it; apparently slide bite is a problem with this design. Still; the huge gaps between parts, the very rust-colored finish... it's something that a tribesman with a hammer in the Khyber pass might take pride in, but it's damn rough for a mass-produced product. Karden has commented on several other eyebrow-raising flaws of the design. An unacknowledged champion it is not.
But the GSh-18 does have some novel features that are worthy of note and investigation. Take note, aspiring pistol designers who want to design a Glock-killer (I'm pretty sure S&W execs sit in front of a giant poster of Gaston Glock, chanting "To the last, I grapple with thee; From Hell's heart, I stab at thee; For hate's sake, I spit my last breath at thee." over and over again). This design has some spiffy features that deserve copying.
How spiffy? Let's start with the fact that the slide isn't a single machined piece. It's two stamping and a machined lockup insert permanently attached to each other with a removable breech block:
Again, try to ignore the rough quality of the actual construction, and look at the contours of the parts. The radial ring of locking splines inside the slide is separated from the rest of the slide by a slight step. Furthermore, going from the rear portion of the slide to inside the locking ring this inside diameter gets larger, while going from the muzzle end back this diameter gets smaller. Looking inside the return spring tunnel, we see an acute inside angle between the locking ring and the return spring tunnel. All of these features show that the forward part of the slide is comprised of three parts that are permanently attached together. The locking ring is one piece that is most likely broached before being attached to the main portion of the slide and then to the return spring tunnel front piece.
This picture shows that the breech face of the slide is a separate part that comes off for disassembly. There are several small advantages of this arrangement. Instead of laboriously machining the slide from a single piece of bar stock, the breech face can be made separately and inserted into a comparatively simple slide that is "U" shaped in cross section.
Laboriously making the slide from a single piece of bar stock, from Brian Nelson's tour of the STI factory
In fact, the KBP Instrument Design Bureau has gone one better on simplifying the construction of the slide. Look at it carefully:
The sides and top of the slide are of a consistent thickness everywhere. That's right; the GSh-18 has a stamped slide! Albeit, it's one of the thickest stampings I've ever seen in a personal firearm. This is rather similar to early SIG P220 series handguns:
A comparison of an early, stamped SIG P226 above and a later milled model, from TTAG
Considering that the stamped SIG P226 was changed to a milled slide to prevent the slide and breech block from separating when firing very hot ammo, it is impressive that the GSh-18 uses this sort of construction given that it is designed for a steady diet of the extremely energetic 7N31.
For high-volume this sort of slide construction would be much cheaper and faster than the all-milled construction seen in the widely-copied Austrian pistol (The Glock With a Thousand Young). The difference might not be large, but as I've said before, anything in a pistol design that's even slightly cleverer than a Glock deserves attention. Additionally, the two-piece construction of the slide would make caliber conversions easier. A caliber conversion kit would only need to consist of a new barrel, breech block and magazines for the new caliber.
The GSh-18 is a rotating barrel pistol design. This itself is nothing new; the patent on that system of operation dates to 1897, but the implementation is unusual. In a typical rotating barrel pistol, the locking occurs at the rear of the barrel, near or in the ejection port and is effected by a few large lugs. The Beretta PX4 is typical:
Beretta PX4 from the Genitron review
In the GSh-18, however, the locking occurs near the front of the barrel, on the rearward of the two sets of radial barrel projections.
The forward projections are not locking lugs; they are beveled on the front and lack witness marks from locking. Furthermore, the locking ring has only one set of splines. The purpose of the forward pseudo-lugs is not clear to me, but they are probably for some prosaic purpose like keeping shit from getting in from the front of the gun.
There are a few advantages to this arrangement versus the traditional rear location for locking lugs in a rotating barrel pistol. In a typical rotating barrel pistol with the locking lugs near the firing chamber, there must be a large amount of dead space inside the slide to accommodate the locking lugs when the slide recoil to extract and eject. This gives most rotating barrel pistols fairly chunky slides:
CZ 07 with tilting barrel on the left, Grand Power P1 mk 7 with a rotating barrel on the right. From the Walther forums.
The GSh-18's locking lug arrangement neatly sidesteps this problem, although the designers ignored this fact. GSh-18 has a very wide slide with a lot of free space inside:
GSh-18 and PYA compared
So the designers of GSh-18 discovered a solution to one of the drawbacks of rotating barrel locking, even though they did not take advantage of it!
Because the slide is stamped, and stampings (especially of that thickness) are somewhat limited in how many fine details and contours they can have, the interaction between the slide and the frame works differently in the GSh-18.
Like other short-recoil automatic pistols, the barrel and slide of the GSh-18 are locked together at the moment of firing. Recoil flings the barrel and slide rearward, which causes the lug on the bottom of the barrel to ride over a helical cam cut into a machined piece of steel located in the frame (this piece also acts as a locator for the return spring, and a mount for a spring-loaded claw whose purpose will be discussed shortly):
The barrel then stops against this piece while the slide continues recoiling. This causes the slide to extract the spent case and eject it. The slide runs out of velocity as it compresses the recoil spring. Once it has completely compressed the spring, the slide begins moving forward, which causes it to pick up a new round from the magazine. Up to this point, the operation of the GSh-18 is like any other recoil-operated pistol.
The difference is with the feeding of the new round into the firing chamber of the barrel. In most other designs there is some interference geometry between the slide and barrel that prevents the barrel from creeping forward from the force of the round being fed into it. If the barrel were allowed to creep forward, it would slide back over the helical cam cut and move into the locked position. This would cause the locking ring splines to bounce off of the locking lugs when the slide came forward, and the gun would not go into battery. But the GSh-18 cannot be made with this sort of detailed interference geometry because the slide is stamped, and making this approach impractical.
Instead, there is a large, claw-like lever on the right side of the frame. When the barrel and slide initially retreat during recoil, this claw snaps over a rim on the right side of the barrel. This claw forcibly holds the barrel to the rear until the slide levers it open at the right moment for locking to begin.
This locking claw allows the use of a simple stamped slide, but it has some advantages beside that. In a normal pistol, the interference geometry between the slide and barrel causes some amount of friction. This means that the area where the slide rubs against the barrel is a critical lubrication point:
Lubrication points for a Glock pistol, from the USA Carry lubrication gude
So the GSh-18's slide loses a little less energy from this rubbing, and is also made a little less sensitive to the condition of the lubrication around the barrel.
This is probably as good a place as any to mention that certain features of the GSh-18 bear more than a passing resemblance to the ill-starred Colt All-American 2000:
The multiple, radially symmetrical locking lugs of the barrel (relocated on the GSh-18 to the front, of course), the two-piece construction of the slide and broad similarities make me wonder if the All-American 2000 was a starting point for the design of the GSh-18. If so, it would make the GSh-18 the second time that this design family with visionary qualities was let down by sub-standard manufacturing.
Perhaps the third time is a charm.