The Russian PKM 7.62 Machine Gun
By Oleg Volk
The PKM, Modernized Kalashnikov Machinegun, is one of the most common modern GPMGs. Designed to fill the same role as the German MG3, American M60 and Belgian MAG58, it provides surprisingly good performance and reliability despite having to use tapered rimmed 7.62x54R ammunition. The original PK was adopted in 1961, with the much lighter PKM superseding it by the end of the 1960s. At the time, it supplanted the much heavier and labor-intensive SGM43 and RP46 machine guns. Since the PK family spawned a half-dozen variants overall, this article will address only the specific early production PKM to which I have access.
PKM is a gas-operated, long recoil design based on a stamped and folded receiver.
The metal is thicker than on the AKM, has welded-on reinforcements and more numerous cross pins for greater strength and rigidity. Like the MG3, it has stamped corrugations, but the overall weapon is substantially lighter at 16.5 lbs. For comparison, MG3 and M60 weigh in at 23, MAG58 aka M240G at 26. While the weight of a GPMG itself is only a fraction of the entire loadout, a 200-round belt doubles the weight of a PKM, but it does enable hand-held fire with 3.5-lb, 50-round belts. Although PKM may be light enough for hand-held use, being no heavier than the classic 30-06 Browning BAR, it lacks any kind of forend. The shooter may hold it by the barrel handle or by the rigid 100-rd ammunition belt box snapped under the receiver, but none of these holds is particularly steady. A more recent development of PKM, the PKP or “Pecheneg,” adds a proper forend for more mobile use while dispensing with interchangeable barrels. Non-mounted use is also complicated by the left-side ejection of fired cartridge casings that tend to hit the shooter’s support hand.
The cyclic rate depends on the ammunition and can vary from 700 to 750rpm. The standard 24-inch barrel makes full use of the powder burn and has heat endurance of about 400 rounds in rapid fire or 1,000 rounds in sustained fire at half the rate.
While barrel replacement is simple–open the top cover, shift the barrel retainer latch to the left, pull the barrel forward by the handle–the latch may be too hot to touch with unprotected fingers so a groove is provided for using a bullet head or small tool. The handle also levers a “Stuck” barrel that is carboned in place, very handy in heavy use. Even if the gun isn’t reloaded for further firing, the bolt face should not be left in contact with the hot chamber to avoid damage to the extractor spring.
Zeroing can be done individually for each barrel, as both elevation and windage are changed with moving the front sight post. Gas adjustment is done with the three-position regulator integral to the piston tube. While the gun fires only full-auto from an open bolt, the weight of the moving parts isn’t great enough to disturb the aim of a first shot substantially, and the trigger is good enough to permit firing of single rounds. The rotary SAFE/FIRE selector is in front of the pistol grip on the left. Sights are typical Comblock post and rang-adjustable style, notch graduated to 1500 m, with point-blank at around 330 m. The rear sight is quick-adjustable for windage to compensate for environmental conditions or leading a moving target. Once the barrel heats up, centered sights suffer from heat shimmer, something addressed in the newer Pecheneg by the addition of a barrel shroud.
In our tests, accuracy was quite adequate from a bipod but extremely poor from the standard tripod. The recoil, while fairly mild thanks to long-stroke operation and reasonable rate of fire, was sufficient to lift the front leg of the tripod after the first shot. For good results, the tripod must be sandbagged, staked or otherwise immobilized. Intended primarily for long-range use, the tripod may be used in conjunction with optical sights installed onto the standard side-rail on the left of the receiver. As with the British L86, PKM is sometimes used as a designated marksman weapon, though bursts are used instead of precise single shots. With 10 to 12 rounds in the air before the first bullet arrives on target at long range, it offers a way to ambush enemy troops without requiring full sniper training or equipment of the Russian troops.
PKM uses non-disintegrating metal belts made in 25-round segments, usually factory loaded to 100-, 200- and 250-round lengths. While the emptied belt handing off to the side can catch on foliage, a 100-round belt is only about 2-feet long, so it won’t drag on the ground during a move. In general, only short belts are used without containers, while 100-, 200- and 250-round belts are kept in plastic or metal containers clipped to the underside of the receiver. Besides keeping ammunition clean, they serve to make the weapon steadier–and the 250-round box more than doubles the weight of a PKM, though that weight changes as the contents are fired off. Belt filling machines exist, but they can be filled by hand with minimal difficulty.
Loading is done with the top cover open, and the first cartridge should be placed in the claws of the cartridge gripper. The loaded ammunition comes from the right; emptied links hang from the left. Like the original Maxim gun, as well as Browning machine guns, the PKM uses a two-stage feed. The first motion of the bolt withdraws a cartridge backwards from the belt; the return motion positions it for chambering. Both happen with a single motion of the non-reciprocating charging handle. This method is more complicated than a push-through like the M60 or MAG58 but is typical for machine guns using rimmed ammunition. With 7.62x54R, this permits fully enclosing belt links at the cost of a slightly longer receiver.
While laminated wood furniture of the early PKMs gave way to plastics, the shape of it remained the same. Standard hold uses support hand on the bottom of the stock to control muzzle rise. Bipod legs of fixed length may be folded forward or back towards the operator, giving an improvised forward grip.
The rotary bolt fits in the carrier in a way very similar to AKM rifle. The gas piston is attached to the bolt carrier with a hinge. The bore is chrome-lined to resist corrosion, as is typical for Soviet small arms. Take-down is quite simple and broadly similar to the rest of the AK family, with the difference of the gas tube being on the bottom. While the gas tube is fixed, it is accessible from the front once the barrel is removed.
Overall, the PKM is among the most successful GPMG designs of the 20th Century. Lightweight and robust, it has an excellent record of reliability and longevity along with considerable combat effectiveness. Accomplishing that with the cartridge first introduced in 1891 and finalized around 1908 was no small feat. Despite some ergonomic quirks, the PKM is a fairly well laid-out design without major flaws. With over a million built, this machine gun is likely to continue in military and paramilitary use for decades.
This article first appeared in Small Arms Review V21N4 (May 2017) |
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