PK machine gun

The PK (Russian: Пулемёт Калашникова, transliterated as Pulemyot Kalashnikova, English: "Kalashnikov's machine gun"code: eng promoted to code: en ), is a belt-fed general-purpose machine gun, chambered for the 7.62×54mmR rimmed cartridge. The modernised variant is known as the PKM, which features several enhancements over the original PK design including a more ergonomic design.

Designed in the Soviet Union and currently in production in Russia, the original PK machine gun was introduced in 1961 and the improved PKM variant was introduced in 1969. The PKM was designed to replace the SGM and RP-46 machine guns that were previously in Soviet service.

The PK remains in use as a front-line infantry and vehicle-mounted machine gun with Russia's armed forces and has also been exported extensively and produced in several other countries under license.

The Main Artillery Directorate of the Soviet Union (GRAU) adopted specification requirements for a new 7.62 mm general-purpose company and battalion-level machine gun that was to be chambered for a rifle cartridge in 1955.

In 1958 a machine gun prototype the Nikitin-Sokolov PN1, developed by G.I. Nikitin and Yuri M. Sokolov, successfully passed field tests. Based on the results of the tests it was decided in 1960 to manufacture a batch of Nikitin-Sokolov machine guns for service tests and then put the machine gun into production at the Kovrov Mechanical Plant. However, the PK had flaws, the main flaw being that the machine gun did not resist water and snow very well. Water and snow had a tendency to enter the gas piston. If, after firing, the machine gun was in the water, then after two or three shots the machine gun could fire exclusively only shot by shot. After a single shot, the shooter had to reload the machine gun and move the slide manually two or three times. The army therefore asked Nikitin to solve this problem, but the engineer took too long to resolve this problem. In order to force Nikitin to work faster, the Main Artillery and Missile Directorate decided in 1958 to restart the competition. For that a team of Izhevsk Mechanical Plant designers, headed by M.T. Kalashnikov, and further consisting of V.V. Krupin, V.N. Pushchin, A.D. Kryakushin, as well as Startsev, Kamzolov, Koryakovtsev, Yuferev, joined the competition. Kalashnikov and his team accepted the task while at the same time, they were already working on the design of the AKM and the RPK. Kalashnikov accepted the task despite his workload and the fact that Nikitin's PN1 had already been chosen by the army and that the latter was supported by certain ministries and senior officers. Their machine gun prototype was based on the well-proven gas-operated rotary-bolt design of the Kalashnikov-pattern arms.

The Kalashnikov and the Nikitin-Sokolov prototypes underwent service tests in the Central Asian, Odessa, and Baltic Military Districts, as well as at the Vystrel officer training courses in late 1960. The Main Missiles and Artillery Directorate and the Ministry of the Defence Industry preferred the Kalashnikov design. The PK could resist water perfectly, but it was also much easier to maintain and manufacture, because it reused the same ammunition bands as the Maxim or SG-43, while the PN1 used a new type of bands which was not yet in production at the time. Furthermore, according to Kalashnikov, its competitors attempted to bias the test by asking operators to lower the rate of fire because of overlapping bands during long bursts. There was also another incident during the test, according to Kalashnikov, the recoil of the PN1 was poorly distributed and a large part ended up in the stock; the pressure was so great that one of the soldiers responsible for testing the PN1 broke his cheekbone.

Based on the test results, the army preferred the Kalashnikov design. In 1961, the 7.62x54R mm Kalashnikov universal machine gun was adopted and put into production. The production of the PK/PKS took place at the Kovrov Mechanical Plant and used the tripod mount and an ammunition belt boxes originally designed for the Nikitin-Sokolov prototype machine gun.

Nikitin's and Sokolov's machine gun design was later used in the 12.7 mm NSV heavy machine gun that was put into production in 1971.