Kalashnikov PK / PKS / PKM / PKMS machine gun (USSR/Russia)

Picture 1: The 7,62x54R Nikitin PN machine gun, from pre-production batch made in 1960 for final troops trials. This gun was almost adopted by Soviet army but then mysteriously lost final trials to Kalashnikov PK

Picture 2: Original Kalashnikov PKS (PK on tripod) machine gun; note partially fluted barrel and long flash hider

Picture 3: Current production Kalashnikov PKMS (PKM on tripod) machine gun, with plain (non-fluted) barrel and short flash hider

Picture 4: current issue, early production Kalashnikov PKM machine gun, loaded with 100-round belt in box and ready to fire

Picture 5: current production Kalashnikov PKMT (PKM Tank) machine gun

	PK / PKS	PKM / PKMS	PKMT
Caliber	7,62x54R
Weight	9 kg (gun) + 7,7 kg (tripod)	7,5 kg (gun) + 4,5 kg (tripod)	10,5 kg
Length	1173 mm	1160 mm	1098 mm
Length of barrel	658 mm	645 mm	722 mm
Feed	belt, 100, 200 or 250 rounds
Rate of fire	650 rounds per minute	650 rounds per minute	800 rounds per minute

Like many others, Soviet military experts closely examined the German ‘heritage’ of WW2, and like many, they found the idea of a Universal (or General Purpose) MG to be very appealing, especially from the logistical and economical point of view. It was therefore decided to replace the separate company, battalion and tank MGs with a single universal design, adaptable to any of these roles. By the early 1950s, requirements were fixed for a new GPMG, firing 7.62x54R ammunition from belts and capable of firing from an integral bipod, an infantry tripod mound or a vehicle mount. After many false starts, by 1956-7 a new design became a favorite, the newly developed Nikitin GPMG. This was a gas operated, air cooled, belt fed weapon with a quick-detachable barrel. It used a fairly typical rotating bolt locking along with less typical (at least, for Soviet guns of the period) features, such as self-regulating gas system and push-through feed system with open-pocket steel belts (incompatible with earlier Maxim and SG-43/SGM belts). By 1958, the Nikitin design was already recommended for adoption, and a batch of 500 guns was ordered for extended field trials with troops, but the situation then became surprisingly complicated. For some reason,General artillery department of Soviet army decided to spur the somewhat slow development of the Nikitin GPMG, and ordered Mikhail Kalashnikov to build his own machine gun to compete with the already established design. At the time Kalashnikov was busy finalizing his improved AKM assault rifle and its companion machine rifle which later became the RPK. However, he accepted the challenge and put some men of his team onto the task of creating their own universal machine gun. It must be noted that this strange situation resulted in a clash of interests between GAU (who literally placed its bet on a new Kalashnikov design) and some elements in Army and Soviet Ministry of Defense Industry, who put their stakes (including their future careers) on the Nikitin design. Exact details of this “undercover battle” are unknown to the general public, but result is widely publicized – the Kalashnikov design won the trials and was subsequently adopted in 1961 as the PK (Pulemet Kalashnikova), in four basic versions: PK LMG (on an integral bipod), PKS MMG (on a universal tripod), PKT (tank coaxial gun with electric trigger and other necessary changes) and PKB (armored personnel carrier version with appropriate mountings). It also must be noted that while PK turned out to be an excellent weapon, people who tested PN often thought that it was actually superior to PK.

The Kalashnikov PK is a general-purpose machine gun which has four basic versions: light machine gun firing from an integral bipod – PK; medium machine gun firing from a universal tripod – PKS; tank coaxial machine gun – PKT; and machine gun for armored personnel carriers (in pintle mounts) – PKB. When the basic weapon was improved in 1969 to become the PKM, all of its versions also received similar designations – PKMS and PKMT.
Copies of Kalashnikov general purpose machine gun were or still are manufactured in Bulgaria, China, Iran, Poland, Serbia (former Yugoslavia), either in original 7,62x54R or in 7,62x51NATO chamberings.

The PK is a gas operated, belt fed, air cooled, automatic only, machine gun. It fires from an open bolt and has a quick detachable barrel. The gas system consists of a gas chamber with a manual gas regulator, and a long stroke gas piston located below the barrel. Locking is achieved through a rotating bolt with dual locking lugs.

The PK uses a two-stage belt feed from steel non-disintegrating belts. Upon the opening stroke of the bolt group, a special claw-shaped ejector withdraws the cartridge back from the belt, and a spring-loaded arm then lowers it into the feed way. Upon the closing stroke of the bolt group, the feed lug on the bolt pushes the cartridge into the chamber. Feed is from the right side only. Spent cases are ejected to the left through a special window in the receiver; this has a spring-loaded dust cover which automatically opens and closes during each reloading cycle. Loading and ejection windows in the feed unit also have dust covers. The feed unit cover is hinged at the front and can be lifted up for loading, unloading or inspection. Standard belts have a capacity of 100 (for PK) or 200 and 250 (for PKS) rounds. Belts are fed from special steel boxes, and a 100-round box can be clamped under the receiver of the PK for better mobility.

The PK is fitted with a skeleton buttstock made from wood and fitted with a hinged buttplate, and a wooden or plastic pistol grip. The rear part of the buttstock houses an accessory / cleaning kit, and a disassembled cleaning rod is stored in the right leg of the bipod. A folding bipod is fitted to the gas tube below the barrel. Each PK gun has a mounting interface which allows it to be placed into the cradle of a universal tripod, designed by Samozhenkov, to form the PKS medium machine gun. This tripod has traverse and elevation mechanisms, and has an adapter for AA use.

Standard sights are of the open type, with a hooded post front and tangent-type rear sight, marked for ranges of up to 1500 metres and with a windage adjustment mechanism. Special versions of the PK have a receiver rail, which accepts mountings of various night sights. Such versions are designated PKN or PKSN, depending on the tactical role.

Modifications.
PKM / PKMS (Modified) is a lightened version of the basic design. The barrel is not fluted, and has a different style shorter flash hider. The feed cover is strengthened by the introduction of stamped ribs. The Samozhenkov tripod is replaced by a new, lightweight tripod designed by Stepanov. This tripod has a special mount for the belt box, so a mounted PKMS gun can be moved through the battlefield without the need for unloading before movement and subsequent loading in a new position.

PKT (Tank) is coaxial weapon used on most Soviet and Russian main battle tanks. It has a heavier, non-fluted barrel. The barrel is also longer than on the PK to provide ballistics similar to that of the earlier SGMT weapon it replaced (to avoid replacement of the expensive tank sights). The gas block is modified and the stock, bipod and pistol grip are discarded. The firing solenoid is attached to the rear of the receiver, but the PKT also retains an emergency mechanical (manual) trigger.

PKB (for armored cars) is the same as the PK but installed on a special mount. However, there were special versions of the PKB fitted with dual spade grips instead of the pistol grip and shoulder stock. Such versions also were used on Mi-8 Hip transport and Mi-24 Hind attack helicopters in window and door mounts through the Afghanistan campaign of the Soviet army.