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Most automatic weapons, with the exception of really weird designs like the Madsen LMG and Hino-Komuro, have a linear reciprocating breech member; either the bolt or a bolt carrier group. This reciprocating member is supposed to move rearward (the recoil stroke) and pull the spent case from the chamber, and then rebound off of a spring to shove a new round into the chamber (the counter-recoil stroke). After the counter-recoil stroke the reciprocating mass should come to a halt in its forward-most position; the "in-battery" position. When the bolt carrier group is in battery the case is entirely surrounded by the walls of the firing chamber and the locking mechanism is fully engaged, so it is safe to fire. Things do not always work ideally, however, and sometimes this reciprocating mass bounces instead of coming to rest. This is called (somewhat erroneously in the case of gas-operated weapons) "bolt-bounce." Andrew Tuohy removed the buffer weights from the buffer in an AR-15 to make the action bouncier for illustrative purposes: There are two ways that bolt carrier rebound can be a problem. In extreme cases the bolt carrier will rebound, but a combination of high friction in the action and weak return springs will mean that the bolt carrier gets stuck and does not go back into battery. Hopefully the designer was smart enough to design the thing so that it absolutely cannot fire when it is out of battery, because out of battery cartridge ignition is an excellent way to convert a firearm into a pipe bomb. If they were so wise, then there will be a failure to fire of some variety. Generally speaking a weapon has to be unusually dirty, worn, or poorly designed for this problem to occur. Return springs are usually strong enough to get the moving parts into battery even if they aren't fully compressed. I have, however, witnessed this problem in German K43 rifles because they are a pile of suck and fail. But they're pretty. The second, more likely problem only rears its ugly head in fully auto fire. In most full auto weapons there is an auto-sear, which a secondary sear which releases the hammer as long as the trigger is depressed. The auto-sear is tripped by the bolt carrier during counter-recoil, usually when or just before the bolt carrier goes into battery. If the bolt carrier rebounds off the front of the receiver and the timing is just wrong, the hammer (or striker) will hit the bolt carrier when it is slightly out of battery. Again, competent designs have means of preventing out of battery ignition and the attendant facial and manual reorganization that tends to go with that. However, when the hammer or striker hits the out of battery bolt carrier its kinetic energy will be spent. This means a failure to fire. Early M16s had rebound problems, particularly during full auto fire. Originally the buffer was intended simply to be a hollow spring guide, but a problem with light primer strikes forced a redesign of this component in 1966. This image, from the patent for the improved buffer shows the series of sliding weights that were added to the buffer. These work like the sliding pellets in a deadblow hammer and arrest the tendency for the bolt carrier to bounce. The additional mass had the added benefit of slowing down the velocity of the bolt carrier, which reduced wear on the parts and lowered the cyclic rate of fire, which improved full auto control. The HK roller-retarded blowback guns, owing to their extremely high bolt carrier velocities, have a strong tendency to rebound unless somehow checked. The solution HK engineers hit on is an anti-rebound claw: Labeled as the "bolt head locking lever" in this diagram. This is a spring-loaded claw mounted on the bolt carrier that grabs the bolt head as the bolt carrier group goes into battery. The lever essentially ratchets into place with friction, providing enough resistance to being re-opened that the bolt carrier does not rebound. The FAMAS, which has a similarly insanely high bolt carrier velocity, solves the problem in a very similar way. In this case, however, the charging handle is the anti-rebound device. The arrangement is similar to the locking catch on an AR-15's charging handle, except that it's much more robust because the catch is responsible for arresting the rebound of the entire bolt carrier. There are other ways still to arrest the rebound of the bolt carrier. The Ruger MP-9 (the one designed by Uziel Gal, not the insanely over complex B&T product of the same name) is supposed to have a spring-cushioning pad at the front of the receiver which brings the bolt to a stop instead of bouncing. The upcoming Desert Tech MDR has, by one account, "an asymmetrical [bolt carrier] face. This is accomplished with a protruding boss on one side of the carrier. As the carrier moves forward to go into battery, the asymmetrical face contacts the barrel extension first. Tolerances within the axial motion of the back end of the carrier group permit the energy to be redirected through a sideways movement. This micro-movement of the rear end of the carrier impedes the bounce and assures full function of the weapon, especially in select-fire operation." Large caliber autocannons often have complex, articulated secondary locks that prevent bolt carrier bounce, since autocannon bolt carriers are enormous and have a great deal of residual kinetic energy. So, when I read that the SIG MCX has some problems with full auto function that sound suspiciously exactly like the same problems the M16 had prior to the addition of the weighted buffer (the same weighted buffer the MCX does away with), I can only roll my eyes. This is nothing new, and there are a half-dozen ways of fixing it. Do your homework.

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.

It is time to explain The Aglockalypse. This is the handgun that killed handgun design in the West. Nobody has had any new ideas worth mentioning on the mechanical design of service handguns since this design came out. Almost every major arms manufacturer in the West makes what is materially a Glock clone; albeit with a few small embellishments and their own logo stamped on the side. What Makes a Glock a Glock? Almost every mechanical contrivance in small arms design was invented about one hundred years ago by some Austro-Hungarian noble you've never heard of or by John Moses Browning. It's about 50/50. Most of small arms design these days consists of applying new materials and manufacturing techniques to old ideas (which may have been unworkable at the time), or by taking a lot of old ideas from different sources and mixing them together in some way that's complimentary. The Glock pistol design is no exception; the ideas were not novel, but putting them all together proved an absolutely world-beating combination. 1) Polymer Frame An H&K VP-70, the first production polymer-framed pistol. Polymer-framed pistols were not an original idea, but at the debut of the Glock 17 they were still a fairly new idea. Glock proved the concept to be mature, and it provided the Glock with a huge advantage over the competition. Traditional metal-framed pistols are made by taking a hunk of metal, either a casting, billet or forging, and cutting away everything that isn't pistol-shaped: This translates to a lot of machine time and a lot of expensive alloys that end up as shavings on the floor. The frame of the Glock was much faster and cheaper to make. Some metal inserts were put into an injection mold (which admittedly is an expensive device, but you pay for it once), and then hot, liquid plastic was squirted into this cavity to form the frame. The entire process takes less than a minute. Cost-wise there is no way for a metal-framed pistol to compete with a polymer-framed one, apples to apples. For very large contracts the math tilts even further in favor of injection molding, since one-time capital costs are a large percentage of injection molding costs while ongoing costs are smaller, while ongoing costs for machining stay largely the same. Gaston Glock was very aggressive about pursuing large contracts (notably the NYPD, which was an early coup), which helped him best use this advantage. 2) The Glock locking system Glocks use a linkless Browning tilting-barrel short recoil system and lock the slide to the barrel via a large rectangular lug machined into the barrel that fits into the ejection port. Glocks were the second major pistol design to combine these two concepts, the first being the SiG P220 series. Ejection port of a Webley automatic pistol, showing the square breech section of the barrel locked to the slide via the ejection port. The barrel translates diagonally. Cross section of a Browning hi-power. This was the first mass-produced pistol to use the linkless short recoil system. The barrel locks to the slide via a series of rings in the barrel that tilt into corresponding grooves in the slide. SiG P220 This operating system is robust and reliable, and fairly easy to manufacture. It has a few theoretical flaws, such as the barrel being slightly off-angle during the extraction of the spent case, the pivot sitting below the barrel and thereby raising the bore axis, and the necessary clearances for the movement of the barrel degrading accuracy. In practice these objections are immaterial. Glocks are absurdly reliable, have a low enough bore axis and only a unusually skilled shooters would notice the mechanical contributions of the precision of the pistol over their own wobbling aim. 3) The Glock Fire Control System The Glock fire control group is an elegant combination of several ideas. Again, most of the ideas in the Glock fire control group had antecedents, but their combination and execution in the Glock was very clever. The trigger transfer bar is a complex shape, but it is stamped from sheet metal and so quite cheap to produce. It also combines several functions into a single piece, including enough safeties that Glocks are reasonably safe to carry even though they lack an external safety. The complete lack of a machined metal hammer, and the clever trigger dingus-lever were also cost savings over traditional pistol design. There are several other incidental design features of the Glock pistol, but these three are in my opinion the ones that allowed it to gobble up market share because they economized manufacture. They are also the three features that the overwhelming majority of Western pistols designed since the Early '80s copy unashamedly. Victims of the Aglockalypse When Gaston Glock first entered his creation in the Austrian Army pistol competition, nobody in arms design had heard of the guy. Longstanding Austrian arms company Steyr was quite confident that their own GB pistol would win the competition. This is basically the pistol equivalent of the couple making out in the back of a convertible at night in a horror movie. It is remembered only as the first in a long list of casualties. Instead, not only was the Steyr GB to lose the competition, but it would fade from the marketplace without making much of an impression anywhere. This is a shame, in my opinion, because the Steyr GB has a few good ideas that deserve a second look, such as the two-position-feed magazines (seen otherwise only in rifles, SMGs and Russian pistol designs), and the truckbed-liner crinkle finish. The design also has some good features for economy of production and excellent mechanical precision, but really, on the whole, it's completely inferior to the Glock. These pistols have a really poor reputation for being unreliable and wearing out quickly, and while Steyr fans will claim this is in large part due to inferior license-produced versions from the United States, nobody argues that even the Steyr-made GBs have anything on the nearly bomb-proof Glock. Also, they're enormous. As far as the Glock was concerned, the Steyr GB was just the first blood. It wasn't enough to best a local competitor; the Glock would obsolete an entire generation of automatic pistol designs. In neighboring Germany, Heckler and Koch's flagship pistol offering was the P7. The P7 has many admirable features. Like the Steyr GB it has a fixed barrel and excellent mechanical precision. It is also very slim and has an extremely low bore axis. It also has the most hideously complicated fire control system ever seen in a pistol that isn't a revolver: A pistol like the P7 could simply never be made cost-competitive with the Glock, much less by a company like HK which usually errs on the side of high performance rather than low cost. Walther, the other big German small arms manufacturer, was busy making the P5: No, the picture isn't reversed. The ejection port is indeed on the left side of the P5, which is because the P5 is nothing more than a slightly re-worked P38 of World War Two vintage. The frame is aluminum, the barrel is shorter and the fire control group has some detail improvements, but it's otherwise the same, right down to the dubious rotating-block locking system. It didn't even have a double-column magazine. Just another outdated design for the Glock to drop-kick into the dustbin of history. Longtime Belgian designer FNH was pushing the Browning BDA, a pistol so boring that I can barely write about it while remaining awake. This is basically a Browning hi-power with a double action trigger somehow shoehorned in. Given how the Browning hi-power trigger works, this is not exactly a straightforward conversion, and this would invite curiousity were it not for the fact that this pistol carries with it a highly stiffling aura of impenetrable boringness. I seriously cannot bring myself to care. Across the Atlantic, in gun-happy America the Glock would face stiff competition from hardened, skillful American firms that had more to offer than face-lifted wartime designs and botique gas-delayed guns. The rugged American outlook on law enforcement provided a stiffly competitive market for quality peace officers' weapons. Haha, I kid. They were just as complacent and mediocre as everyone else. Sturm Ruger Co, one of only two publicly traded firearms manufacturers in the US, released their P-series of pistols in the mid eighties. It seems a little uncharitable to list these chunky pistols as victims of Glock superiority, since they sold in decent numbers and aren't terrible. But victims they were; the design was simply outdated. The strangest feature of the P-series pistols is that the older designs in the family use a swinging link to cam the barrel in and out of engagement with the slide. While the swinging cam arrangement works well enough, and several fine weapons use it (e.g. 1911, Tokarev), with modern materials and manufacturing tolerances the linkless system is simply better because it doesn't produce the grinding movement caused by the short radius of the link swinging radius, and because it has fewer parts. The P series was also reasonably cost-competitive because most of the parts are cast before machining to final dimensions. Sturm Ruger has exceptional expertise in firearms castings, which has long given them the edge in pricing. Castings can be made very closely to the final shapes required, which saves a lot of machining time. However, this gives many of their designs a bloated, water-retaining look. The other publicly traded firm, Smith and Wesson, was doing reasonably well with a whole family of automatic pistols that I absolutely do not care about. They have names that end in "9", have generally Browning-ish insides, and the single stacks look pretty and elegant. There are also some double stack variants, and some are in stainless. Something something unbuttoned pastel shirts, designer Italian pants and cocaine. Oh look, there goes my mind, wandering again because these pistols are BORING, MEDIOCRE AND I HAVE MORE IMPORTANT THINGS TO CARE ABOUT. OH LOOK IT'S ANOTHER PRE-GLOCK SINGLE STACK METAL FRAMED PISTOL. This time it's from Colt. It is a well-documented fact that Colt's senior management spent the entire 1980's doing nothing but licking their own genitals like cats. I don't even know what this pistol is called. Do you know what it's called? Do you care? Do you think Colt's management cared? Of course not. So let's make up a name. We'll call it... the Colt Elantra. This Colt pistol is more interesting, and has an operatic history. Unfortunately, that opera is Wagner's Ring Cycle. Nobody did anything that made sense, and by the end there was a fat lady singing and then everything burned to the ground. The pistol was originally designed by Reed Knight and Eugene Stoner, who were by that time already living legends for designing the combat robots that crushed the communist menace decisively at the Battle of Arrakis. The design was mechanically fascinating, featuring an unusual rotating barrel, roller-bearing supported striker fire control group, polymer frame with screw-on grips, and an unusual, but very appealing slide stop design. Alas, Colt completely screwed up the design by making it too big, making the trigger pull too long and too heavy, and by making it not work. Even without the stiff competition from Glock, the design would have been an ignominious failure. All of the above designs, though in some cases initially successful, would face dwindling market share against the cheaper-to produce Glocks. Their respective firms sat down and quickly came to the conclusion that they were not as clever as Gaston Glock, but that was OK since he had done the clever for them. Saint Gaston Converts the Industry to Glocktholicism The first of the Glock clones to hit the market, the S&W Sigma is so similar to the Glock that some of the parts will interchange: This resulted in some drama, hasty design changes and a settlement payment for an undisclosed amount. Next came the Walther P99: This pistol introduced the interchangeable backstrap, which was generally considered a good idea. It also introduced several option trigger modules, including a DA/SA version with a decocker button on top of the slide. This is bid'ah, and heresy against the Glockspel. The great genius of the Glock is that it's simpler and cheaper to produce than competing designs. One cannot successfully outcompete the Glock by taking a Glock and adding a bunch of extra shit to it. Then you just have a more expensive Glock, which, ipso facto, will not outcompete an Orthodox Glock. HK was, until recently, one of the last holdouts of Albigensianism hammer-fired handguns, being unable for some time to bring themselves to make an unabashed Glock clone. However, their USP series is, compared to their previous offerings, quite Glocky. They have switched to the Browning short-recoil, linkless tilting barrel design with a barrel that locks to the slide through the ejection port. By 2014, however, HK had entered into full Glockmmunion, and introduced the VP9; a striker-fired, polymer framed pistol: FNH of Belgium initially responded with the FN Forty-Nine, which is like a Glock but with a DAO trigger: However, they swiftly recanted of their error and introduced the FNP, FNX and finally the FNS, an all-but-Orthodox Glock clone: Steyr introduced the M9 series of pistols, which were actually designed by a former Glock employee! These are basically Glocks, but slanted, with weird sights and that say "Steyr" on the side instead of "Glock." In 2007, Ruger was converted and introduced the SR-9: In 2005, S&W made a slightly more refined clone called the M&P: There are several versions now, including some for blasphemers that have external safeties. Colt has yet to introduce a Glock clone; their strategy regarding this portion of the handgun market remains enigmatic. Survivors For various reasons, a few metal-framed designs have survived and remain commercially competitive. But there is reason to think that their days are numbered. The Beretta M92 series is mechanically rather similar to the Walther P-39, except it has a double stack magazine. The widespread adoption of this essentially sound, but uninspired design, by many militaries not the least of which is the US Army, has bought the design staying power. However, the recent announcement that Beretta, too, has discovered how to stencil their own name on to the side of a Glock shows that they haven't come up with anything better either. The CZ-75 design continues on as well, in no small part because producing a CZ-75 clone is a right of passage in Turkey that all adolescents must pass in order to be recognized as men. Turkish CZ-75 clones are so common at firearms trade shows that they are often used for paperweights and juggling. When there is heavy snow it is common to keep a bucket of Turkish CZ-75 clones handy to pour onto icy patches to get better traction for a stuck vehicle. But the latest offering from CZ proper, the CZ P-09 is beginning to look a lot like Glock-mas: Polymer frame, barrel that locks into the ejection port... It keeps the distinctive CZ-75 slide-inside-frame and fire control group, but it's more like a Glock than a CZ-75 is. The trendline is unmistakable. There are a few other hold-outs, but by and large the firearms industry has found Glock's recipe to be compelling. To be cost-competitive, new designs copy these innovations to a greater, rather than a lesser degree. This has meant a stultifying lack of creativity amongst pistol manufacturers, as more and more of them decide that their best bet is to copy a thirty five year old design.

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.

Now that Weaponsman has linked the forum, I guess it's time to post actual content. No more dumb one-liners or jokes about the Turkish government's policy towards Kurds or Sherman burning down Atlanta. For at least five posts. I think that's all I can manage. The internet has been a mixed blessing for gun nuts. On the one hand, it allowed for much freer exchange of information that was previously exclusive to a few experts. The notorious mil-spec chart (no longer up to date) that circulated around ar15.com years ago is probably a big part of the reason that AR-15 manufacturers stepped up their game and started turning out generally excellent products. On the other hand, the internet has been an excellent vector for the spread of nonsense. In my experience, relatively little of the misinformation is maliciously spread; it's mostly the result of people not knowing what the hell they are talking about. In particular, a great deal of nonsense would be ignored if people could just remember high school physics. A lot of mystical, physics-defying rubbish is said about weapons reliability in particular. Reading nothing but internet fora circa the late 2000s, one could easily come away with the impression that the AR-15 is uniquely unreliable thanks to the direct impingement action. This is despite the fact that coating aluminum or steel in a thin layer of carbon powder would actually reduce its coefficient of friction. Actually, the dynamics of automatic weapons are not difficult to understand. An often overlooked metric in the reliability of gas-operated automatic weapons is the mass ratio between the bolt and the bolt carrier. I first became aware of the importance of this ratio when reading a US Army manual on small arms design at Forgotten Weapons. Just to be clear, this ratio is only important in the way I'm describing in gas-operated, some recoil-operated and inertia-operated weapons. The dynamics for retarded blowback weapons, like the H&K G3, are quite different. In a gas-operated weapon, there is a bolt that is locked rigidly either to the barrel or to the receiver at the moment of firing. This contains the pressure of the cartridge firing (which is alarmingly high). The projectile is pushed down the bore. As soon as it passes the gas port, some of the gas begins pushing the bolt carrier to the rear. The work done on the bolt carrier by the propellant gas from the gas port is the only energy that the bolt carrier will have to complete the cycle of operations. This means that the total work required to: unlock the bolt pick up the bolt extract the spent case cock the hammer compress the return spring operate the belt mechanism (if it's belt fed) cannot exceed the amount of energy that is initially fed to the bolt carrier. Ideally, the bolt carrier will have some excess reserve of energy so that it can complete the cycle of operations even if the gas port is slightly clogged, the ammunition is slightly under-loaded, or the receiver is dirty (et cetera). However, if the bolt carrier has too great a reserve of kinetic energy, it will still be travelling rapidly when it reaches the end of its travel, and then it will violently jerk to a halt or possibly even bounce off of the rear of the receiver. This increases wear on the weapon, and in a shoulder fired weapon can cause the sights to jerk off target. There are two ways to increase the energy capacity of the bolt carrier; make it go faster (in gas-operated weapons, this is done by the simple expedient of enlarging the gas port), or make it heavier. There are practical limits on how fast the bolt carrier can reciprocate; according to Brassey's, a good rule of thumb is 15 m/s is the maximum practical velocity of the bolt carrier. Above this velocity things start to break. Cases can be torn apart instead of cleanly extracted from the firing chamber (the Soviet SHKAS fast-firing aircraft machine gun required special high-quality ammunition with extra-strong cartridge cases), springs lose their strength in fewer cycles, and the lifespan of the moving parts is reduced due to increased fatigue. Making the bolt carrier heavier also has practical limitations; the weapon becomes heavier not just from the heavier bolt carrier, but also from the larger receiver needed to enclose it. In shoulder-fired weapons the sights will be thrown off target by the porpoising motion of the reciprocating center of mass. The act of picking up the bolt after it is unlocked is of particular interest, because it can absorb a great deal of the energy from the bolt carrier. The bolt is picked up and accelerated by the bolt carrier, after which they are stationary relative to each other. This means that there is an inelastic collision between the bolt carrier and the bolt, and in an inelastic collision kinetic energy is not conserved even though momentum is. The initial kinetic energy of the carrier is 1/2MV^2. The initial and final momentum of the system will be the velocity of all moving mass times that mass. This works out to a reduction in kinetic energy after the pickup of the bolt. For instance, if the bolt and bolt carrier have equal mass, after bolt pickup the velocity of the bolt carrier group will be half of what it was before and the mass double what it was before. That works out to half the kinetic energy of the bolt before pickup. Generally the equation for the remaining energy after bolt pickup will be: E2=E1*(1+1/R)-1 Where E2 is the bolt carrier group kinetic energy after bolt pickup, E1 is the bolt carrier kinetic energy before pickup, and R is the ratio of mass between the bolt carrier and the bolt. If anyone is terribly curious I can show the derivation of this. According to the US Army Ordnance small arms design manual hosted at Forgotten Weapons, designers should shoot for a mass ratio of 3 or better, which would translate to 75% energy retention after bolt pickup. More is better, but there are strong diminishing returns here; a weapon with a mass ratio of 2 will have 66% remaining kinetic energy after bolt pickup, but a design with a mass ratio of 4 will have 80% conservation. As the mass ratio gets larger and larger, the percentage of bolt carrier kinetic energy after bolt pickup will approach 100% asymptotically. Again, to keep designs lightweight, the ideal way to achieve this would be to make the bolt as light as possible. However, in a locked breech weapon in 5.56 NATO, the bolt has to withstand peak chamber forces of 22.7 KN (or 5,100 lbs if you're using haram infidel non-SI units). It therefore has to be fairly robustly constructed, and making a lightweight bolt that is still safe over the operating life of the weapon is not an easy engineering task. When determining the ratio for actual weapons, it's important to define exactly what masses are involved. What we are looking at is the ratio of the moving mass that is accelerated by gas that will have kinetic energy available to accelerate the stationary mass. Take a look at this slow-motion video of an FAL firing: The piston follows the bolt carrier back far enough that its energy is available for bolt pickup, even though it's a separate piece from the carrier and doesn't translate through the entire distance that the bolt carrier does during cycling. So, for the purposes of determining bolt carrier to bolt mass ratio, the piston of the FAL counts as bolt carrier mass. In an AR-15, the firing pin rides in the bolt carrier, is pressed forward against the bolt carrier during the initial acceleration, and therefore counts towards the mass of the bolt carrier group. However, the buffer is not rigidly attached to the bolt carrier, so its kinetic energy cannot contribute towards bolt pickup. Therefore it does not get counted. Obviously any extractors, cam pins, and miscellaneous other parts get counted toward the part they ride with. Strictly speaking some portion of the mass of the return spring should be counted (and Chinn's excellent The Machine Gun has equations for calculating the impact of spring mass on reciprocating parts dynamics), but I was too lazy to include this because it's really, really small. So, let's see how well actual designs do: Semi-auto TAR-21 carrier group mass: .623 kg bolt mass: .055 kg Carrier to bolt mass ratio: ~10:1 Notes: It is impossible to remove the return spring from the bolt carrier of the semi-auto TAR-21 for some arcane reason, so I had to guesstimate on this one. However, whatever the exact number, the TAR-21 has an exceptionally high bolt carrier to bolt mass ratio, and that is one of the (few) outstanding features of the design. Using a stationary cam pin that is located in the bolt carrier that acts upon stationary cam grooves in the bolt is one way that the design improves the mass ratio, and this unusual feature is worth emulating in other designs. Sadly, the design as a whole is not as elegant and mass-efficient as the bolt carrier group is. SIG-551A1 carrier group mass: .505 kg bolt mass: .093 kg Carrier to bolt mass ratio: 4.4 Notes: Disappointingly low, but still above the magic 3:1 figure. The SIG rifles show one of the advantages of a reciprocating charging handle; the mass of the charging handle is adding to the kinetic energy of the bolt carrier, rather than being deadweight. The bolt on the SIG rifles is fairly massive, in part because the firing pin is located in the bolt rather than the bolt carrier. 7.62x39mm AK carrier group mass: .505 kg Bolt mass: .080 kg Carrier to bolt mass ratio: 5.3 Notes: The charging handle and piston are one piece with the bolt carrier on an AK, which helps improve the mass ratio. The bolt is fairly massive, in part because the firing pin is located in the bolt. Semi-Auto SCAR-H carrier group mass: .713 kg Bolt mass .066 kg carrier to bolt mass ratio: 9.8 Notes: In the AR-18 derived bolt carrier designs the cam pin is rigidly attached to the bolt, and therefore increases its mass. Also, the bolt must be sturdy enough to withstand the stress of 7.62 NATO ammunition. Despite this, the SCAR-H manages a monstrous 9.8 mass ratio in a rifle that's still reasonably light for an automatic 7.62 NATO weapon.

As a current side project stops and starts according to my whims, I figured I might as well create here and keep updated a list of rules/guidelines for design of lightweight automatic/autoloading rifles and other weapons. Here's what I have so far: 1. Volume is mass; smaller means lighter. 2. The lightest, strongest shape is the sphere, and it has the least surface area for its volume. Cubes, though conceptually simple, should be avoided where possible. All light weapons desire to approach the shape of the cylinder, an elongate sphere. 3. (For conventional-layout weapons) Adding one ounce of weight in front of the point of balance adds two in total. 4. The primary mass is the primary driver of the total system mass. As a rule of thumb, adding 1 gram to the bolt mass adds 10 grams total to the rifle. 5. The only way to achieve exceptional lightness of weight is to reduce weight wherever possible, no matter how minor the savings in each case. The best way to lighten a rifle by 10% is not by cutting the weight of one component dramatically, but by reducing the weight of all components by 10%.