Dushka: The Soviet Fifty Caliber

Dushka: The Soviet Fifty Caliber

The beginning of the HMG saga: Imperial German Tank- und Fliegerabwehrmaschinengewehr Modell 18, or TuF MG 18, a Maxim chambered in 13 mm x 92SR round for the Mauser T-Gewehr AT rifle.

It was not only the tanks that the Dushka defended.  As the Lend-Lease trucks with a .50 Browning mounting ring over the cab were delivered, the idea of employing Dushkas for road convoy aerial defense caught on with the Russians, but in a slightly different manner – they did not design either ring or pedestal mounts, but simply put their .50-caliber guns with their M1938 universal mounts on the flatbed of GAZ-AAs, ZiS-5s, GMCs, Studebaker US-6s as well as Dodge WC-52s – thus creating a prototype of the now ubiquitous ‘technical.’  In armored trains, the Dushkas were employed as anti-aircraft weapon, in most cases set on a naval pedestal mounts.

The Soviet Navy VMF (Voenno-Morskiy Flot) also used many Dushkas.  When the war begun in 1941, the VMF had a total 787 DShKs, but during the war 4,018 more were delivered for ship armament, as well as 1,146 on universal tripods for naval bases aerial defense.  The ship-borne Dushkas were mounted in pintle mounts, shielded or not, but also in more complicated shielded twin (vertically set) 2M1 mounts or even a quadruple armored gun box.

Late during the war a modernized model of the Dushka was designed, 250 of which were manufactured in 1945 by the Saratov plant, and some even managed to get battle-tested in Manchuria.  It was introduced into the inventory of the Soviet Army in 1946 as ‘12.7-mm Dyegtyarova-Shpagina Krupnokaliberiy Modernizirovanniy obraztsa 1938/1946 goda (DShKM)” or 12.7mm Dyegtyarov-Shpagin Modernized Heavy Machine Gun Model of 1938/1946 (DShKM), and the GAU catalog number was 56-P-542М.  The modernization was carried out by a team of young KB-2 designers, headed by Kiryl I. Sokolov and Alexander K. Norov.  The main feature of that modernization was a completely new belt-feed module, whereas the feed sprocket was dispensed with and replaced by a flat, shuttle-type belt transporting unit.  The new belt-feed was not only less complicated, smaller and cheaper to manufacture, but it also enabled the feed direction to be changed according to the position of the feed plate and pawls.  The Dushka was the only Soviet machine gun fed from the left, and some users were complaining that this is making gun crew training unnecessarily difficult. The belt itself has changed as well. It still remained an articulated belt of open links, but the links were no longer connected with spirals and coming in 50-round lengths only.  They were now hinged, with pins and sheaths formed by bending the link blank’s tabs, and made semi-disintegrating, in 10-round lengths.  The amount of changes in the links made them both not interchangeable, even though they look deceptively similar.  The new links have strengthening ribs pressed into them, making them too thick for the older sprocket feed to clear.  Now that the belt was made in 10-round increments, the ammo box was found to easily take 60 rounds of ammo, instead of the former 50 – without any dimensional changes.  Another important change was the barrel fastening method.  In the original Dushka, the barrel was screwed-in and then wedge-locked, thus placed semi-permanent, and only detachable at repair shop.  The new barrel was just inserted and wedge-locked, which made it easier to replace – but still by no means a QCB.  The war experience fully backed the choice of air-cooling in connection with the open bolt firing mechanism.  That coupled with a massive barrel proved to be fully adequate to absorb the heat of firing – anti-aircraft fire occasionally called for long bursts of fire, but the targets were exposing themselves to the fire seldom, and for a short time.

Rumanian deeply-modernized DSK-UM of the Cugir Plant, with a new multi-baffle muzzle device on the quick-change barrel, firing the .50 BMG round – and fed from M9 links! This is the newest – and probably the last ever – incarnation of the Dushka.

Production shortcuts in the modified weapon mostly involved exchanging the milled parts for stamped ones, and eliminating exotic high-grade steels.  The re-shaped all carbon steel operating rod now had a 400% longer service life, while the manufacturing cost was cut down to a quarter of the former price, and stoppage ratio fell due to a simpler feed from 0.8% to 0.36%.  Looking from outside the easiest way to differentiate between the two Dushka models is to take a look at the feed cover – the earlier cylindrical shape gave way to a flat-top.

Dushka: The Cold Warrior
After WW2, DShK/DShKM remained the basic vehicular anti-aircraft defense heavy machine gun of the Soviet Union and ComBloc countries.  The troops’ AA defense was taken over by twin and quadruple 14.5mm Vladimirov guns, and later on by ZU-23-2 twins and ZSU-23-4 Shilka quadruple SPAAGs, but it was the Dushka that crowned every T-54/55 tank and many other vehicles, amassed for the future liberation of Western Europe.  At first only the heavy tanks sported them, but with the advent of guided anti-tank missile-armed helicopter gunships in the early 1960s, virtually every tank or armored vehicle was issued one: tanks, self-propelled artillery, recovery vehicles, even troop commander’s APCs.  Then, with APCs getting armored roofs, which started in 1960s, the Dushka was replaced by a successful BPU-1 turret with coaxially mounted 14.5mm and 7.62mm machine guns, first developed for the BRDM-2, but later added to all BTR-60/70/80 family and Polish/Czech SKOT/OT-64 wheeled and BTR-50/TOPAS/OT-62 tracked families.  On T-54/55s the machine gun mount was a direct descendant of the spring-equilibrated ring mount of the IS-2, also fitted around the loader’s hatch, with loader firing it standing on his jump-seat.  The mount was fitted with a new collimating sight, the improved and much smaller K-10T, fitted in a special sheet-metal pressed box, protecting it in travel.  The gun itself of course retained the ladder sight, which could be used in emergency, but rather for ground target work.  With time all deficiencies of the old lady were exposed, and in the late 1960s a new, modern heavy machine gun was designed from scratch by Grigori I. Nikitin, Yuri M. Sokolov and Vladimir I. Volkov.  This new gun, code-named Utios (or Rock) was introduced into the inventory of the Soviet Army in 1972 as NSV.  As with the original Dushka, it had a rather troubled childhood, and the first series-manufacture guns were actually issued only four years later, in 1976.  From that point on old Dushkas were gradually retired: all new tanks and other vehicles were delivered with NSVs, the older AFVs were mothballed or sold abroad with their Dushkas, joining the other license-built ones exported throughout the Third World so far, mostly by the Chinese.

The Dushka Inside Out
DShK is an air-cooled, gas-operated automatic weapon, with a long-stroke gas piston, permanently attached to the operating rod.  It fires from open bolt, thus trading the relative simplicity and efficient cooling between the shots for a rather lamentable single shot accuracy. The gas chamber with a three-vent size gas regulator is situated under the barrel.

New semi-disintegrating cartridge belt in 10-round length with pressed strengthening ribs and connected with pins.

The operating rod with its side mounted cam lug interacts with the swinging feed operating cam (the ‘cylinder hand’ that rotates the belt feed rotor).  In the DShKM the swinging action actuated the feed pawl, pushing the linked round onto the two stripper horns, taking over the role of the crescent- shaped stripping claw.  They are now a part of the feed tray rather, than the receiver.  In the original Dushka with sprocket feed, the feeding was indirect, despite the open link belt being employed: it took two cycles for the belted round to be stripped and transported through two positions of the sprocket onto the bottom feed line.  In the modified Dushka the feeding is still only semi-direct, but the whole operation is now performed within a single cycle of the mechanism: on recoil the lug-operated swinging arm propels the feed pawl, which transfers the belt across, while stripper horns lever the round out of the link, allowing the cartridge depressor to push it down through a slot in the feed tray, into the path of the counter-recoiling bolt for chambering and firing – an improvement over the original feed, but still a long way to the kind of direct feeding employed by Western style GPMGs.

The operating rod upper projection mounts a shaped firing pin, holding the bolt impaled upon it and governing the swinging in and out of the locking flaps.  The locking flaps shape and operation is identical with the DP light machine gun, but of course the size is bigger.  While this locking mechanism resembles the Kjellmann-Friberg machine gun and German G43 semiautomatic rifle in principle, it is actually quite completely different – starting with its being reversed.  While in Kjellmann-Friberg and G43 the firing pin cams the front parts of the locks out into receiver abutments, rotating them around the rear edge of the locking flap, in the Dyegtyarov guns it cams the rear parts of the locks out, rotating them around the front edge.  As long as the firing pin is forward, they cannot revert into their respective nests in the bolt sides.  On recoil, the operating rod moves rearward, pulling with it the firing pin.  The locks are no longer supported, and fold into the bolt nests, thus unlocking and releasing the bolt.  On rearward travel the bolt with flaps moves into the narrow part of the receiver, when the flaps cannot deploy, and the very same lugs that in forward position pushed the locks sideways, now keep the firing pin securely back, away from the bolt face.

The firing pin is two-piece, compared with the smaller integral firing pin of the DP – the firing pin point is a separate, spring-loaded part to avoid overstressing leading to breakage.  The ejector is of a rod-type, housed in an oblique channel inside the bolt, tipping the case down into the ejection opening on impacting the buffer.  The extractor is of claw-type, operated by a flat spring, all set in the bottom part of the bolt.

The late 1990s offered Rumanian M1938/46 Dushka on a somewhat modernized M1938 Universal Mount with small-diameter, rubber-tired wheels, and a new shield. This one was still chambered for the 12.7mm Soviet ammunition.

The trigger mechanism allows fully automatic fire only, but due to low rate of fire single shots are easily achievable.  Cooling fins cover most of the barrel length in all Dushkas except the later Chinese and Pakistani/Iranian ones.  The T-shaped, bottom hinged trigger lever operating the sear by lieu of a trigger release lever has two triggers on the extremities of the upper bar, which can be reached with either index finger, while holding the vertical wooden handles at the buffer housing.  Caution: there’s NO automatic trigger safety of any kind, so if you do not intend to fire immediately after cocking the action, it is advisable to apply the manual safety (in right lower rear part of the receiver, rotate forward for Safe), thus blocking the trigger release lever, transferring the trigger movement to the sear.  The buffer housing has two individual buffers with superimposed heavy duty cylindrical springs, the upper for bolt, and the lower for operating rod.  The Dushka responds well to climate extremes, and can be operated in any temperature, from -50 to +50°C (-58 to 122°F).  The upper temperature limit is mostly limited by what the crew is willing to endure, as there’s virtually no cook-off risk – the gun only chambers a round when the trigger is pressed and there’s not enough time for the heated chamber to cook-off the round before the bolt locks and the operating rod strikes the cap with the firing pin.

Dushka has got her own metallic sights, comprising of a hooded front post height- and windage adjustable, and leaf sight with windage-adjustable, clickable U-notch, with sight settings from 100 to 3,500 (M1938) or 3,300 m (M1938/46) in 100 meters increments.  For anti-aircraft firing a tubular shoulder stock can be attached, and various other sights were used.  The M1938 and M1941 sights were ring sights with a peep mounted on a special arm, fitted to the optical sight base on the upper mount (M1938) or to the sight ladder (M1941).  They also differed in a way of setting and adjusting the ring sight base.  The later model of the anti-aircraft sight, the M1943, was very much different in concept from the earlier ones.  It is a so-called ‘area value leading sight’ and has two rings, one each for both of the gun crew members.  The assistant gunner had a ring with a small aircraft silhouette on three leading wires and his task was to keep that silhouette or leads depending on speed on the target, while transferring his point of aim to the gunners’ ring with a hand-turned crank.  The movement of the crank, transferred through a complicated system of cogwheels and transfer bars, moved the vertical pointer of the gunner’s ring, along which there was a series of aiming points, chosen by the gunner according to the ‘area value,’ being a quite complicated ratio between the length of the aircraft and its angle of approach, range and speed.  It took much training and lightning-fast calculation on the part of the gunner to master this complicated instrument, and the ST-HB-07-03-74 ‘Small Arms Operation And Identification Guide – Eurasian Communist Countries’ manual specifically warns its future U.S. or Allied captors not to use it for unit aerial defense, because of the level of expertise needed to use the sight efficiently.  Although it needed that expertise and turned the gun crew into self-propelled computers, this sight had a distinct advantage over the Vietnam era U.S. computing sights in being worth peanuts in comparison while having no need for electricity…