One of the world’s great unsung light machine guns is the Ruchnoy Pulemyot Degtyaryova (“Degtyaryov’s handheld machine gun” in Russian), more commonly known as the RPD. In 1944, Vasily Degtyaryov designed this 7.62x39mm (M43) gun, which was based on the Pulemyot Degtyaryova Pekhotny (DP) light machine gun designed in 1928—the RPD was vastly improved.
While the DP light machine gun fired the bull-size Soviet 7.62x54R cartridge using a Lewis Gun–type, 47-round, top-mounted, “pan” drum magazine, the RPD fired the intermediate-size, 7.62x39mm cartridge, a less powerful but more modern round developed during World War II. The RPD also used an uninterrupted belt-feed operated by a shuttle-feed system, similar to that of most other modern belt-feed designs. The RPD’s belt was a “push-through” type, as pioneered by Germany before WWII with the MG 34. The RPD’s belt is normally housed in a drum-like can that attaches to the bottom of the gun; however, this can is not a magazine but merely a container.
PKs, RPKs & RPDs
Except for size and other improvements, the PK and RPD share a number of similarities. As with the PK, the RPD operates by a long-stroke gas piston mounted beneath the barrel. The rear section of the piston contains the operating rod, bolt, bolt carrier and striker. On either side of the bolt is a locking lug, and being of the tilt- or prop-bolt variety, these relatively long locking lugs are referred to as “flaps.” They swing out laterally to engage locking shoulders in the sides of the machined steel receiver, and thus the RPD’s bolt is more of a rear-locking style.
At the rear of the striker is a dual cam system, which acts on the locking flaps to force them out into the receiver recesses when in battery and withdraws them back into the bolt as the carrier moves to the rear. The RPD fires from an open bolt. When the right-side-mounted cocking handle is pulled all the way to the rear to the cocked position, the bolt remains there ready to be fired.
When the trigger is pulled, the entire operating rod and bolt group speed forward under pressure of the mainspring or recoil spring. As the bolt goes into battery, the striker continues, with its cams forcing the flaps outward and with their rear ends engaging the locking shoulders in the receiver. If a cartridge is in position, the top of the bolt strips it forward out of its link and down into the chamber, where the striker would have ended its journey by firing the round. If the trigger were held back, the sequence would continue until the belt was empty.
The RPD was ready to be mass-produced near the end of WWII but was put on hold when Germany surrendered. With the Korean War looming, the RPD was finally put into production, soon becoming the standard light machine gun of the Soviet Union and the Warsaw Pact states. As successful as the RPD was, when the RPK (a light machine gun variant of the AKM) was designed in the early 1960s, it began to replace the RPD in first-line units for logistical reasons, as well as for cost and weight savings.
Nevertheless, the RPD was the standard light machine gun of the Viet Cong and the NVA during the Vietnam War. While it did not have the range of the U.S. M60, the RPD was shorter and had almost half the M60’s weight. This made the RPD extremely successful in ambush assaults, where only two or three 50-round belts were needed. But if many more than 150 rounds were fired at a time, one of the RPD’s main shortcomings would quickly become apparent. Where most other belt-fed machine guns have quick-change barrels, the RPD does not. This is not critical in of itself, but the RPD’s wooden handguard, which is mounted around and contacts the barrel, becomes quite hot after only a couple of hundred rounds and soon begins to smolder or even catch fire, leaving the bipod the only part of the weapon for the support hand to hold. In spite of this, RPDs have remained in use worldwide, their handguards (many of which are hand-made or otherwise improved) often replaced. The gun is that good. And the ammunition it uses is one of the world’s most common. This is why the RPD came to the attention of DSA Arms Inc.