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Found this instructional manual on screw machine (think of it as all mechanical CNC machine that takes forever to tool up) setup, and it got me thinking about how much of a lost art running one of these things is. CNC lathes and machines in general are obviously much easier to set up but they still cannot match the potential of a multiple spindle screw machine that can spit out parts like nobody's business (they can come quite close however). Another topic of conversation that fascinates me is the concept of the multiple spindle milling machine, at first glance it seems like an inelegant solution to the problem of increasing mill production, but that's just me. Does anyone have any idea if form tools were ever used to cut the outer profile of parts in one pass on these machines? Perhaps I am looking at this from the wrong way however, once production becomes so important that you need to improve the output of a screw machine, it might be best to look at other options (die casting, stamping, etc.). One last note, I wanted to see what people think of stamping sheet metal gears. Is this just a novelty thing someone does for their CAD portfolio or something actually viable? More sources below... How many spindles are really necessary? Running a multiple spindle machine in a small part run world
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.
I recently had an opportunity to take a look at a PS90. These are the extended-barrel, semi-auto only version of the FN P90. Aside from the lengthened barrel, barrel shroud, and modifications to the fire control group, they are identical to P90s. The P90 was the correct idea at the correct time for FN Herstal. Prior to its introduction, they had been focused on the BRG-15, a 15.5mm very heavy machine gun: This potent weapon fired a monstrous 15mm, later 15.5mm round that edged out the 14.5x114mm round for raw power. The idea, as I understand it, was that Conventional Forces Europe treaty restrictions limited the number of vehicles armed with autocannons that signatory nations could possess. Heavy machine guns were substantially less restricted. While the BRG-15 had a number of desirable features, such as selectable dual ammo feed and APDS ammunition, it did not sell, and FNH needed badly a new, hot product. Enter the P90. FN had been working on a new type of ammunition for a PDW for some time. Their initial ammunition concepts had been quite exotic, featuring APDS projectiles fired from a rimfire cartridge case: FN had grasped that a modern army is mostly support personnel; mechanics, cooks, clerks, etc, and actually only a minority are front-line combat troops. If they could sell a weapon to arm second-line troops, and if they could get this new class of weapon to be NATO standard, they would be fat and happy once again after all the money they'd wasted on the BRG-15. H&K thwarted them on the NATO standardization front, but FN did get comfortably back in the black, as the P90 has sold quite well. The design of the P90 is, shall we say, heavily inspired by the Steyr AUG. The AUG features a cast aluminum receiver, a polymer stock which houses the trigger, fire control components and magazine well, and a bolt carrier group that slides on two guide rods with internal return springs. This is the aluminum receiver of the P90: Here are the telltale porosity marks of casting: Here is the polymer stock, showing the magazine well and some of the components of the trigger group: You can also see that there is a seam between the two stock halves; wide enough to admit sunlight in some places. And here is the back of the stock, showing the hammer pack taken out of it: Finally, here is the bolt, which rides on twin guide rails with external return springs. I guess that's a little different: The P90 is a simple blowback design, which greatly reduces the cost of manufacture because there are no breech locking components that need to be made to tight tolerances or made of high-quality material. However, this does place some constraints on the ammunition design. Here are the sockets in the receiver, astride the barrel breech where those rods fit into: FN wasted hardly any time coming up with something new; they simply put their new 50 round magazine into a straight-blowback AUG, and set about selling it. There is actually a lot about the design that suggests it was somewhat rushed. Late in the development of the P90, the ammunition was shortened by a few milimeters. Instead of completely redesigning the whole gun and magazine: The magazines simply feature an indentation that fills the space the original, longer rounds used to. From a production engineering standpoint, the P90 has many admirable features. It has a minimum of machined features, and the machined parts are very simple shapes. The receiver is cast with some machining to final dimensions, and the stock is injection molded. Casting and injection molding are both well-suited to cheap, high-volume production. Parts that would be machined in other designs, such as the fire control lockwork and hammer, are injection molded in the P90. The P90 also features a number of parts that are semi-permanently affixed to larger assemblies, and can only be serviced at an armorer level: The charging handle and the charging handle return spring are looped around the barrel, and are not user-serviceable. The trigger transfer bar and magazine catch components are sandwiched in-between the two stock halves. The return springs cannot be de-mounted from the bolt either. This is actually typical of non-US designs; the degree to which the end-user can service and modify the weapon is limited to basic field stripping. I remember being shocked at how fiddly and difficult it was to pull the bolt from the bolt carrier group in a TAR-21, only to find out later, reading the manual, that this is supposed to be an armorer level repair. Apparently the bolt cannot even be removed from the bolt carrier on the new Cz 805 without tools: To American shooters, the P90 comes off rather poorly. It doesn't disassemble as far as they would expect, and it looks very slapped together utilitarian. For FN it was exactly the right design at the right time. It had wide appeal and could be made in massive quantities cheaply.
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.