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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. Earliest Origins 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: AK-107/AK-108 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. AEK-971 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-1 AKB 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.

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.