DShK

The DShK 1938 (Cyrillic: ДШК, for , "Degtyaryov-Shpagin large-calibre") is a Soviet heavy machine gun with a V-shaped "butterfly" trigger, firing the 12.7×108mm cartridge. The weapon was also used as a heavy infantry machine gun, in which case it was frequently deployed with a two-wheeled mounting and a single-sheet armour-plate shield. It took its name from the weapons designers Vasily Degtyaryov, who designed the original weapon, and Georgi Shpagin, who improved the cartridge feed mechanism. It is sometimes nicknamed "Dushka" (a dear or beloved person) in Russian-speaking countries, from the abbreviation.
History.
The requirement for a heavy machine gun appeared in 1929. The first such gun, the "Degtyaryov, Krupnokalibernyi" (DK, "Degtyaryov, large calibre"), was built in 1930, and this gun was produced in small quantities from 1933 to 1935. The DK was fed from a drum magazine of thirty rounds, and had a poor rate of fire. Shpagin developed a belt feed mechanism to fit to the DK in 1938, giving rise to the adoption of the gun as the "DShK 1938". This became the standard Soviet heavy machine gun in World War II.
Like its American equivalent, the M2 Browning, the DShK 1938 was used in several roles. As an anti-aircraft weapon it was mounted on pintle and tripod mounts, and on a triple mount on the GAZ-AA truck. Late in the war, it was mounted on the cupolas of IS-2 tanks and ISU-152 self-propelled guns. As an infantry heavy support weapon, it used a two-wheeled trolley which unfolded into a tripod for anti-aircraft use, similar to the mount developed by Vladimirov for the 1910 Maxim gun. It was also mounted in vehicle turrets, for example, in the T-40 light amphibious tank.
In 1946, the "DShK 1938/46" or "DShKM" (M for "modernized") version was introduced.
In addition to the Soviet Union and Russia, the DShK has been manufactured under license by a number of countries, including the People's Republic of China (as the "Type 54"), Pakistan, and Romania. In Russia, it has been mostly replaced by the more modern NSV and Kord designs. Nevertheless, the DShK is still one of the most widely used heavy machine guns.
In June 1988, during the conflict in Northern Ireland known as "the Troubles", a British Army Westland Lynx helicopter was hit 15 times by two Provisional IRA DShKs smuggled in from Libya, and forced to crash-land near Cashel Lough Upper, south County Armagh.
DShKs were also used in 2004, against British troops in Al-Amarah, Iraq.
In the 2012 Syrian civil war, the Syrian government said rebels used the gun mounted on cars. It claimed to have destroyed, on the same day, 40 such cars on a highway in Aleppo and six in Dael.
It is often erronously claimed that the DShK can fire .50 BMG (12.7x99mm). Though both have a diameter of 12mm, the rounds are not interchangeable, because the case length and head dimensions are different. The myth began in US weapons intelligence manuals referring to the DShK as being "12.7mm (.51-caliber)" and the assumption was made that this was intentional to accommodate interchangeable ammunition.
Anti-aircraft sight.
Many DShKs intended for the close anti-aircraft role were fitted with a simple mechanical sighting system that helped the gunner properly account for "lead" in order to hit fast-moving targets.
The system consisted of two circular disks mounted side-by-side in a common framework. On the right, in front of the gunner, was a large "spider" sight that contained a line of small metal rings running from the center to the outer edge. On the left, in front of the loader, was a smaller disk with several parallel metal wires. In some examples, the sight was installed with the loader's sight on the right.
To use the sight, the loader/observer would spin his disk so the wires were parallel to the target's direction of travel. A shaft running between the two turned the gunner's sight to the same angle. The gunner would then sight through one of the metal rings based on the estimated range and speed.