Dushka: The Soviet Fifty Caliber

Dushka as an AA weapon on a Soviet armored train, 1943. Note the naval adjustable-height pedestal mount and the M1941 AA sight, as well as tanker helmets and coveralls worn by the crew.

In 1931 both Pastukhov’s and Dyegtyarov’s machine guns were given a comparative trial, and the latter won – on account of the more powerful round and the abysmal performance of the rival.  Nevertheless the narkom, although aware of the deficiencies, rushed the prototype DK-31 into mass-production, ordering the designer to iron-out the wrinkles during the mass-production preparation.  The first 50 weapons were delivered two years later in 1933.  Despite several dozen modifications introduced during that period, the serial-produced DK was still as bad as the original.  In 1935, after several hundred guns were manufactured, the GAU threw the towel in and the production line was stopped.  The Red Army still had no heavy machine gun, but at least the narkom has been given a lesson that rushing things is only good when you hunt down the fleas.  It wasn’t a lasting lesson for the concerned, unfortunately.

Enter The Dushka
The 1933 premature start of the mass-production did not end the development process of Dyegtyarov’s heavy machine gun.  There was still much to be improved, and nobody was more aware of the fact than the designer himself.  He and Kladov desperately tried to improve the DK, but to no avail.  Dyegtyarov was fighting on far too many fronts, introducing four machine guns at the same time.  Fortunately, the others were unqualified blazing successes, so he did not fall from grace.  In 1933 the dust settled, and he was able to work at a less frantic pace.  The apparent down-side of the magazine feed turned his attention towards a belt feed, that he has tried to avoid so far, emulating his mentor.  They were both of the opinion, that belt-feds were unnecessarily complicated and that magazines were better for tactical application.  This was still an era of closed link cloth belts, necessitating a complicated multi-stage indirect feed in Maxim or Browning guns.  Direct feed was still only a magazine virtue, with a few belt/magazine hermaphrodites like Hotchkiss or Breda rigid belts.  The success of ShKAS and ShVAK fast-firing aerial machine guns, feeding rimmed-case ammunition from disintegrating links at the pace of over 1,000 rpm (ShKAS was able to shoot at a phenomenal rate of fire of 1,800 rpm from a classic “one bolt-one chamber-one bbl” gun) were proof enough that belt-fed guns can be successful – but at a price of considerable complication of the design.  The Shpitalniy guns had very complicated – although deceivingly simple-looking – rotor feeds, whereas the belt was transported by rotation of the feed rotor, while cartridges were simultaneously stripped rearwards from the links in a multi-stage process by lieu of slides operated by ellipsoidal cam path cut inside the feed casing – vaguely resembling the Minigun feed but working backwards, i.e. pulling rounds back rather than pushing forward.  Dyegtyarov was still wary of the complication, and instead he delegated the task of designing something along these lines, but definitely simpler and dust-tolerant enough for ground work, to the young upstart designer of his KB-2 Kovrov design bureau, named Georgiy S. Shpagin (later to design the famous PPSh-41 submachine gun). The result was the 1935 prototype, called DK-34, combining an almost intact DK-31 with a belt feed module designed by Shpagin.

The DShK M1938 HMG on M1938 Kolesnikov Universal Mount in AA role configuration. Unfortunately this museum piece from the Polish Border Guards Hall of Fame has both the M1943 AA sight and shield welded in place – in reality one negates the other.

The Shpagin belt feed employed a feed sprocket, or rotor – resembling an enormous revolver cylinder with chambers cut open.  It was rotated by a sprocket rotating hand (or operating cam), not unlike that of a revolver.  Although this hand pulled rather than pushed, and was propelled by a projection (cam operating lug) of the gas-operated bolt carrier, not by cocking action, the general principle was still that of a wheel-gun.  It even had a ‘cylinder stop’ in the form of an anti-reverse latch to prevent sprocket rebounding and to hold it still, when the bolt traveled underneath, chambering a round transported by the rotating sprocket to the feed position at the bottom.  To load the weapon, after cocking it, one placed the first rounds of the open-linked continuous belt onto the sprocket, with rounds mating between the ribs, and belt going over the tip of the crescent-shaped stripping claw on the right side of the receiver (2 o’clock position, looking from the rear).  Then after slamming the feed cover shut, the loader had to yank hard on a stout wire starter tab, thus pulling the sprocket through and stripping the first two rounds from the belt into the sprocket cells, at the same time transporting the first of these onto the feed line.  The rounds are thus levered out of the links and into the hollows of an advancing sprocket, transporting them to a 6 o’clock position for the bolt to chamber.  Then, after the first shot, on recoil, the operating rod’s cam lug hits the sprocket operating cam, shaped as a yoke at the bottom end of the sprocket rotating hand, advancing the sprocket by another 1/6, stripping the next round from it and transporting the belt, while at the same time presenting another round for the rebounding bolt.  On the return (counter-recoil) stroke the cam operating lug hits the yoke again, resetting the sprocket rotating cam for another cycle.  If fire was interrupted, and the gun was to be cleared, the loader first opened the feed cover, removed the belt, then unlatched the rotor and rotated the feed sprocket by hand to retrieve two rounds already stripped and still present in the feed mechanism.  The gunners were taught to remember that rounds were still present in the feed after the belt was removed – but it was nothing new for them, as their other belt-fed machine gun was a Maxim, which was also famous for remaining loaded after the belt was taken out.  The prototype worked quite well during the 1936 trials, and both gentlemen decided to cooperate on improving the DK further.

Dushka In Service
In April 1938, a series of comparative trials were held, pitting what the creators now called the “DShK-37” against the Western heavy machine guns: the M1921 water-cooled Browning, a .5-inch Vickers and the French Mle 1930 Hotchkiss in 13.2mm.  The closed-bolt designs were more accurate, but the DShK-37 survived both of them in ‘adverse working conditions’ trials and in overall service life – even through two of the opponents were water-cooled.  This was mostly due to a novel feature, a return spring pleated from three strands, for added strength and life, first used in the ShKAS fast-firing aerial machine gun and then transferred into the DK.  Later on, this type of spring was copied by the Germans in the MG-42 – and then it made a world-wide career.

The new heavy machine gun was introduced into the inventory of the RKKA on February 26, 1939, and this time the first series-manufactured guns were issued a mere year later.  The official Russian designation is: 12,7-mm krupnokalibierniy pulyemyot Dyegtyarova-Shpagina obraztsa 1938 goda (Model of 1938 12.7-mm Dyegtyarov-Shpagin Heavy Machine Gun) and the GAU catalogue number is 56-P-542.

A captured early Chinese-manufactured Type 54 DShKM as a trophy in front of the USAF O-Club in South Vietnam.

These guns were issued along with the Model of 1938 Universal Mount designed by Ivan N. Kolesnikov.  The name ‘universal mount’ refers to its being used in both configurations.  In transfer / ground target configuration it is a wheeled mount with a protective shield, not unlike the Sokolov mount for the Maxim.  The most important difference is that instead of a U-shaped thill with two additional AA legs (discontinued after WW1), it now had three tubular legs, which in ground configuration are folded alongside each other, perpendicular to the axis of the carriage wheels.  If aerial targets are to be engaged, the shield and wheels are detached, three legs are extended and spread to form a tripod, allowing training in a 360° arc, with vertical field of fire of -34° to +85°.  This M1938 Universal Mount was an enlarged and much heavier (119 kg with wheels and shield) incarnation of the M1931 universal mount for the rifle-caliber Maxim, manufactured and issued only in limited number – as opposed to the M1938 Dushka mount.

One of the most interesting features of the mount is that it comprises a cocking handle.  The gun itself had no cocking handle of its own, just a socket inside the operating rod’s cam lug, into which a fired case or a cartridge was inserted – and only then the gunner was able to cock the bolt.  In vehicular or other mounts where no cocking slide was at hand, the gunner had an option of using a case or a special cocking handle, usually kept in an oblique tubular holder welded somewhere on the mount.

In the coming war the DShK was called ‘Dushka’ by the soldiers, which not only sounds alike to the DShK abbreviation, but has a meaning as well – its Russian for ‘sweetheart.’  Dushkas proved deadly effective against low-flying aircraft, and in the early phase of the war were quite effective against the armor.  At the time of its introduction in 1932, the B-32 API bullet was an undisputed king of the battlefield: it was able to perforate any tank in service then, and only the heavy tanks, like the French B1bis or 2C, Soviet T-35 or the German BW (later to become known as PzKpfw IV) were immune to Dushka fire.  The proliferation of the thicker-skinned ‘heavy’ tanks in 1940 brought about the introduction of the even more powerful round, the 14.5 x 114, soon used in the AT rifles and Vladimirov heavy machine guns.  The Dushka was not without drawbacks, though.  The gun was heavy, and its moving parts also were heavy – the reciprocating unit (operating rod with bolt) weighed 4 kilograms (8.8 lbs) and was propelled by a powerful spring that, combined, jarred the gun forcibly after the trigger was squeezed, resulting in less than perfect accuracy.  It was rather an area-fire weapon, than point-firing one, and hitting an aerial target with it called for lots of luck on the part of the crew, as well as skill.  Soviet gunners proved to command both, as Dushka wrote a splendid chart of the WW2 history, earning herself a place in the Soviet Army’s inventory for long years to come.

The Soviet T-40 light amphibious tank had a Dushka as primary armament, mounted in turret co-axially with another Dyegtyarov machine gun, the tank DT in 7.62mm.

The First Dushka War
During WW2, the Dyegtyarov-Shpagin heavy machine gun was a frequent sight on the Eastern Front.  The TO&A placed it in anti-aircraft companies of the infantry divisions, and Dushka was the first ever Red Army’s machine gun entirely transported by motor vehicles.  During the war the design was perpetually perfected, both in production methods and design itself.  The most visible change was brought about in 1944, when the early pear-shaped muzzle device was replaced with a ‘hollow disc’ single-baffle one, designed by Rukavishnikov, and patterned after the captured Polish wz.1935 AT rifle.

Before the war, Dushkas were also slated to become the armament of the armored fighting vehicles, initially as the main armor-piercing armament.  In 1936, the magazine fed and less than successful DKs were to be used in a BA-9 6×4 heavy armored car, but because of the problems the DK gave, none of the 100 BA-9s were built, becoming instead the BA-10 with a low-velocity 37mm cannon by lieu of the turrets taken from scrapped T-18 light tanks.  Next came the T-40, a light reconnaissance amphibious tank, armed in 1939 with the perfected DShK.  A year later the T-40 turret with the DShK was used for another heavy armored car, the LB-62, as well as its competitor, the LB-NATI.  Neither of them came into mass-production, though.  Specialized anti-aircraft vehicles were then created, including a 1942 T-90 – a T-70 light tank with a turret sporting two Dushkas.  The T-90 underwent trials but never made it into mass-production, as the same Gorki Automobile Plant (GAZ) in Gorki created at that point a ZSU-37 – variant of the SU-76 self-propelled gun armed with a 37mm M1939 automatic cannon of much better performance.  It was also the GAZ, which designed another armored Dushka carrier, a variant of the BA-64 (armored version of the Soviet jeep, the GAZ-64), called BA-64D.  It took such a lot of work to squeeze the large Dushka into a small turret of the Bobik (as the BA-64s were called by the soldiers), that the prototype was not ready before mid-1943, although the project was started early in 1942.  For lack of space for the loader to operate the AA sight, a novel, very advanced feature was added: the K-8T universal collimating reflex sight, designed especially for this project, patterned after the aircraft sight.  It was that same lack of space that caused another shortcut, this time a lethal mistake, which killed the BA-64D project.  As there was no place for the standard 50-round belt box, the turret was designed for the magazine-fed DK, the auto designers being ignorant as to the abysmal performance of the early gun.  When the very advanced turret design was finally ready, and the flawed gun was built into it, and as the firing trials proved disastrous, the project was finally abandoned in 1944.

But the idea to use the K-8T reflex sight on the Dushkas caught on, and these were added to the DShKs serving as auxiliary local self-defense and AA weapons on Soviet heavy tanks (IS-2, IS-3) and heavy self-propelled artillery (ISU-122 and ISU-152) as of 1944.  The Dushka was mounted behind the loader’s hatch of all these vehicles, on a special ring mount with spring counterweights, enabling fast and easy elevation of the heavy weapon, also serving an additional purpose as recoil absorbers.

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