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 order to force Nikitin to work faster, the Main Artillery and Missile Directorate decided in 1958 to restart the competition.

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.

[4] 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.

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.

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.

[5] The original PK was a development of Kalashnikov's AKM assault rifle and the accompanying RPK light machine gun design that featured stamped receivers.

With the use of a single spare parts kit and two barrel assemblies the service life of the modernized PKM machine gun series is guaranteed for at least 25,000 rounds.

[7] The bolt and carrier design are similar to the AK-47 and other modernised Kalashnikov-pattern weapons, as is the stripping procedure performed to remove those mechanisms from the gun for cleaning.

The lever, which is simplified compared to the prior art, is mounted on the right wall of the receiver and wraps around the bolt carrier with its feed pawl and roller.

The PK general-purpose machine gun U-shaped receiver is stamped from a smooth 1.5 mm (0.06 in) sheet of steel that is supported extensively by pins and rivets.

For additional rigidity and strength the PK receiver features double walls made from 1.5 mm steel plates that are welded together with the U-shaped stamping.

The front sight assembly is mounted near the end of the barrel and consists of a protected open post adjustable for elevation in the field.

PK machine guns that feature a Warsaw Pact side-rail bracket on the left side of the receiver can mount various aiming optics.

On the right side of the field of view a stadiametric rangefinder is incorporated that can be used to determine the distance from a 1.5 meters (4 ft 11.1 in) tall object from 400 to 1,200 m (437 to 1,312 yd).

The skeletonized buttstock, pistol grip and folding carry handle/grip on the barrels were originally manufactured from birch plywood laminates.

Such engineered woods are stronger and resist warping better than the conventional one-piece patterns, do not require lengthy maturing, and are cheaper.

The links are made of 0.8 mm (0.03 in) thick high carbon stamped steel sheet metal that is zinc phosphated and varnished for protection.

For the light machine gun role, the PK is used as the standard squad automatic weapon of the Russian Army.

The PK uses a 100-round non-disintegrating belt contained in a metal box made from an aluminium frame and steel cover that can be attached under the gun's receiver.

The PK is equipped with a simple detachable bipod mounted to the gas cylinder beneath the barrel and in that light machine gun setup is used as a squad-level support weapon.

As with all general-purpose machine guns, tripod and vehicle mountings offer a higher degree of accuracy and control than when used on a less stable bipod.

The 6T2 Samozhenkov tripod mount was earlier envisioned for the Nikitin-Sokoiov machine gun that was not adopted by the Soviet Union.

Hinged tripod legs allow a gunner to fire the machine gun from a prone, a sitting, or a kneeling position.

Modifications include the removal of the stock, a longer (722 mm (28.4 in)) and heavier barrel that adds 30 m/s (98 ft/s) muzzle velocity, a gas regulator and an electric solenoid trigger.

The PKT minimum cyclic rate of fire is 100 rounds per minute higher than other PK-series variants and is usually fed from 250-round ammunition boxes.

The PKMN (ПКМ Ночной: "PKM Night-Vision") is a variant that can mount a night sight for low-visibility operations.

Besides the Shakhin[20] and 1PN116[21] thermal sights and the 1PN119[22] anti-sniper special-purpose night vision sight are available for mounting on PK machine guns that like the PKMN model feature a Warsaw Pact side-rail bracket on the left side of the receiver for mounting aiming optics.

In the early 1990s, as part of the preparations to join NATO, the Polish armed forces were looking for a replacement for the PK-series machine guns then in service.

[24] The modifications included a heavier barrel, a larger chamber, and a redesign of the lock, bolt, extractor, and the entire feeding mechanism.