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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.

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The more I look at it, the more I am sure that the GSh-18 has a milled slide. Note the contours of the top of the slide; these would have to be created with a horizontal mill. Also note that the thickness of the top of the slide is greater than the sides.

As for why the slide is so wide, its to allow for the locking insert. If you look, you can see that the whole geometry of the slide is driven by that locking ring.

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   I don't think they used stamping to make slide. Sounds like some amount of effort is needed to make it work right, which is not what producer of this pistol wants to do. I tink they just pick piece of metal and drill it, with precision of what worker eyes are capable to achieve, until it looks like pistol slide. 

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For me, the biggest indicator that it is stamped is the lack of machining marks on the slide.  If the slide were machined out of a piece of billet there would be ugly milling marks all over all of the contours.  But we don't see that; there are only marks where the barrel steps down in diameter and attaches to the recoil spring guide (which looks like it was flint-knapped).


So either they put way more effort into cleaning up the profiling cuts on the outside of the barrel than they did the actual moving parts, or it was made in some way that doesn't leave such marks.

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Or Lenin's ghostly touch burned it with his ghostly rage so hot it removed all marking on it when he saw the build quality of it.

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Or they sandblasted it.


Possible, but that would mean the FW example was sandblasted and then the cuts on the front of the slide were made.


Also, I don't think that the top of the slide is thicker than the sides:




The cuts are oblique so it looks that way from any angle but dead astern.

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