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68-586: Work on the weapon commenced in 1943. Three prominent Soviet engineers were asked to submit their own designs: Vasily Degtyaryov , Sergei Simonov and Alexei Sudayev . Among the completed prototypes prepared for evaluation, the Degtyaryov design proved superior and was accepted into service with the Soviet armed forces as the 7.62 mm Ручной Пулемёт Дегтярёва, PПД (RPD, Ruchnoy Pulemyot Degtyaryova or "Degtyaryov light machine gun") model 1944. Although

136-573: A Fields Medal in 1970 followed by Grigory Margulis in 1978 and Vladimir Drinfeld in 1990. Soviet technology was most highly developed in the fields of nuclear physics, where the arms race with the West convinced policy makers to set aside sufficient resources for research. Due to a crash program directed by Igor Kurchatov (based on spies of the Cambridge Five ), the Soviet Union was

204-734: A Nobel Prize . The most prestigious government prize awarded for achievements in science and technology was originally the Stalin Prize . After the death of Stalin, the Stalin Prize was renamed the USSR State Prize , and the new Lenin Prize became the top award. [REDACTED] This article incorporates text from this source, which is in the public domain . Country Studies . Federal Research Division . – Soviet Union Recoil operation Recoil operation

272-401: A gas-operated long-stroke piston system and a locking system recycled from previous Degtyaryov small arms , consisting of a pair of hinged flaps set in recesses on each side of the receiver . The movement of these flaps and the resulting locking and unlocking action is controlled by carefully angled surfaces on the bolt carrier assembly. The weapon fires from an open bolt . The RPD

340-400: A barrel to do so. However no one has been able to verify this claim in recent times, although there is another automatic gun that dates from the same year, but its type and method of operation are unknown. Recoil-operation, if it was invented in 1663, would then lie dormant until the 19th century, when a number of inventors started to patent designs featuring recoil operation; this was due to

408-413: A fixed insert inside the receiver housing which passes between the feed horns of the bolt serves as the ejector. Spent cartridge casings are ejected downward through an opening in the bolt carrier and receiver. The RPD has a manually operated lever-type safety mechanism that secures the weapon against accidental firing by blocking the bolt catch when engaged. Unlike Degtyarov's earlier firearm patents,

476-711: A long-recoil–operated shotgun line, the AL-48 , which shares both the original Browning action design, and the "humpbacked" appearance of the original Auto-5. Other weapons based on the Browning system were the Remington Model 8 semi-automatic rifle (1906), the Remington Model 11 & "The Sportsman" model (a model 11 with only a two-shell magazine) shotguns, the Frommer Stop line of pistols (1907), and

544-544: A metallic, open-link, non-disintegrating belt typically holding 100 rounds of 7.62x39 ammunition. Unlike many other belt -fed automatic weapons, where the rounds must be pulled out the rear of the belt and then pushed forward into the chamber, the RPD uses a simpler "push through" design where the rounds are pushed out the front of the belt and into the chamber. At least three variants of the RPD belt were produced. The Russians and Hungarians both produced 50-round belt segments, while

612-409: A modernized version called RPD Carbine . The RPD Carbine has a fluted 17.5-inch barrel, modern front sight, alloy handguard with rails, M249 -type pistol grip and M4 recoil spring tube and buttstock. Because semi-auto RPD variants are manufactured using de- milled parts kits from full-auto RPD machine guns, in order to comply with ATF regulations the full-auto parts must be modified such that

680-469: A new shell has been positioned from the magazine. The bolt is released and forced closed by its recoil spring, chambering a fresh round. The long recoil system was invented in the late 19th century and dominated the automatic shotgun market for more than half that century before it was supplanted by new gas-operated designs. While Browning halted production of the Auto-5 design in 1999, Franchi still makes

748-400: A notch for installing and removing the cleaning jag on the cleaning rod), broken case extractor, front sight adjustment tool, gas tube scraping tool, gas port reamer, spare extractor, spare extractor spring, spare firing pin. There are a number of spring steel "fingers" on the lid of the clam-shell case which press on the contents of the cleaning kit when closed to prevent rattling. One end of

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816-427: A portion of the firearm recoils while inertia holds another portion motionless relative to a mass such as the ground, a ship's gun mount, or a human holding the firearm. The moving and the motionless masses are coupled by a spring that absorbs the recoil energy as it is compressed by the movement and then expands providing energy for the rest of the operating cycle. Since there is a minimum momentum required to operate

884-584: A recoil-operated firearm's action, the cartridge must generate sufficient recoil to provide that momentum. Therefore, recoil-operated firearms work best with a cartridge that yields a momentum approximately equal to that for which the mechanism was optimized. For example, the M1911 design with factory springs is optimized for a 230-grain (15 g) bullet at factory velocity. Changes in caliber or drastic changes in bullet weight and/or velocity require modifications to spring weight or slide mass to compensate. Similarly

952-408: Is hammer fired from an open bolt. The hammer forms part of the rear of the bolt carrier (which is connected to the gas piston), which continues moving forward for a short distance after the round is chambered and the bolt locked, the hammer face then striking the rear of the free floating firing pin which passes through the length of the bolt. Locking occurs by means of lateral flaps located along

1020-408: Is adjusted up or down for elevation using a tool included in the issued cleaning kit. To adjust the front sight for windage, the smaller of the two wrenches on the multi-tool included in the issued cleaning kit is used to loosen the retaining bolt on the front sight clamp. The front sight can then be adjusted left or right for the correct windage, after which the retaining bolt is reinstalled to lock

1088-444: Is an operating mechanism used to implement locked-breech autoloading firearms . Recoil operated firearms use the energy of recoil to cycle the action, as opposed to gas operation or blowback operation using the pressure of the propellant gas. The earliest mention of recoil used to assist the loading of firearms is sometimes claimed to be in 1663 when an Englishman called Palmer proposed to employ either it or gases tapped along

1156-513: Is by Alexander Blakely in 1862, who clearly describes using the recoil of a fired cannon to open the breech. In 1864 after the Second Schleswig War , Denmark started a program intended to develop a gun that used the recoil of a fired shot to reload the firearm, though a working model wouldn't be produced until 1888. Later in the 1870s, a Swedish captain called D. H. Friberg patented a design which introduced both flapper-locking and

1224-478: Is only applied to heavily recoiling firearms, particularly shotguns. A similar system using inertia operation was then developed by Paolo Benelli in the early 1980s and patented in 1986. With the exception of Sjögren's shotguns and rifles in the early 1900s, all inertia-operated firearms made until 2012 were either made by Benelli or used a design licensed from Benelli, such as the Franchi Affinity. Then

1292-458: Is pulled into the gun during the rearward motion of the bolt carrier. The noteworthy flaw in the drum's design is its unreliability in dirty conditions; it can become clogged with filth and other natural elements. The RPD is equipped with a set of open-type iron sights . These consist of a front post and a notched rear sight mounted on a tangent. Both the front and rear sights on the RPD are adjustable for windage and elevation . The front sight

1360-673: Is the toggle bolt design of the Borchardt C-93 and its descendant, the Luger pistol . While the short recoil design is most common in pistols, the very first short-recoil–operated firearm was also the first machine gun , the Maxim gun . It used a toggle bolt similar to the one Borchardt later adapted to pistols. Vladimirov also used the short recoil principle in the Soviet KPV-14.5 heavy machine gun which has been in service with

1428-540: The Browning Arms Company introduced the inertia-operated A5 (trademarked as Kinematic Drive) as successor to the long-recoil operated Auto-5 . Both the Benelli and Browning systems are based on a rotating locking bolt, similar to that used in many gas-operated firearms. Before firing, the bolt body is separated from the locked bolt head by a stiff spring. As the shotgun recoils after firing, inertia of

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1496-475: The Chauchat automatic rifle (1915). The short recoil action dominates the world of centerfire semi-automatic pistols , being found in nearly all weapons chambered for high-pressure pistol cartridges of 9×19mm Parabellum and larger, while low-pressure pistol cartridges of .380 ACP and smaller generally use the blowback method of operation. Short recoil operation differs from long recoil operation in that

1564-564: The RPK and PK machine guns in the 1960s, the RPD was withdrawn from most first-tier units of the former Warsaw Pact . However, the RPD remains in active service in many African and Asian nations. Apart from the former Soviet Union, the weapon was manufactured in China (as the Type 56 LMG ), Egypt (Maadi RPD), North Korea ( Type 62 ) and, since 1956, Poland. The RPD is an automatic weapon using

1632-828: The Russian Soviet Federative Socialist Republic had their own republican academies of science, while the Urals, Siberian, and Far Eastern regional branches of the academy coordinated fundamental science in Eastern Russia. Medical research was coordinated by the USSR Academy of Medical Sciences ( Академия медицинских наук СССР ), which after 1992 was reorganized into the Russian Academy of Medical Sciences ( Российская академия медицинских наук ). Agricultural research

1700-446: The barrel also cause all or a portion of the firearm to move in the opposite direction. The result is required by the conservation of momentum such that the ejecta momentum and recoiling momentum are equal. These momenta are calculated by: The barrel is a moving part of the action in recoil-operated firearms. In non-recoil-operated firearms, it is generally the entire firearm that recoils. However, in recoil-operated firearms, only

1768-468: The Britons Schlund and Arthur. In a long recoil action, the barrel and bolt remain locked together during recoil, compressing the recoil springs. Following this rearward movement, the bolt locks to the rear and the barrel is forced forward by its spring. The bolt is held in position until the barrel returns completely forward during which time the spent cartridge has been extracted and ejected, and

1836-524: The Chinese produced 25-round belt segments. The Russian RPD belts held the rounds in place using the extractor groove. The Hungarians designed a simpler belt that held the cartridges in place using an L-shaped tab at the rear of the belt. The Chinese copied the Hungarian design for their belts, albeit in 25-round lengths instead of 50. RPD belt segments are connected using a round of ammunition that holds

1904-495: The Communist Party. All research, including natural sciences, was to be founded on the philosophy of dialectical materialism . Humanities and social sciences were additionally tested for strict accordance with historical materialism . After World War II , many scientists were forbidden from cooperation with foreign researchers. The scientific community of the Soviet Union became increasingly closed. In addition to that,

1972-638: The RPD was ready for mass production during the final stages of World War II , it was adopted in 1948 and large scale delivery of the weapon did not begin until 1953. During the Vietnam War , the RPD and its Chinese copy (Type 56) served the Viet Cong and the People's Army of Vietnam as their standard light machine gun. After the introduction of the Kalashnikov -pattern support weapons, such as

2040-472: The RPD's return spring is located inside the butt. Like many other Russian-made firearms , the chamber and bore are chrome-lined , greatly decreasing the risk of corrosion and jamming . The weapon has a non-removable barrel with a three-position gas adjustment valve used to control the performance of the gas system. It is also equipped with a folding integral bipod , wooden shoulder stock , foregrip and pistol grip . The firearm strips down into

2108-618: The Russian military and Middle Eastern armed forces since 1949. Melvin Johnson also used the short recoil principle in his M1941 Johnson machine gun and M1941 rifle, other rifles using short recoil are LWRCI SMG 45 and LoneStar Future Weapons RM-277R . An alternative design concept for recoil-operated firearms is the inertia operated system, the first practical use of it being the Sjögren shotgun , developed by Carl Axel Theodor Sjögren in

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2176-709: The Soviet Union served as an important part of national politics , practices, and identity. From the time of Lenin until the dissolution of the USSR in the early 1990s, both science and technology were intimately linked to the ideology and practical functioning of the Soviet state and were pursued along paths both similar and distinct from models in other countries. Many great scientists who worked in Imperial Russia , such as Konstantin Tsiolkovsky , continued work in

2244-527: The USSR and gave birth to Soviet science. The Soviet government made the development and advancement of science a national priority, emphasizing science at all levels of education and showering top scientists with honours. Very large numbers of engineers graduated every year. Soviet scientists won acclaim in several fields, marked by a highly developed pure science and innovation at the theoretical level, though interpretation and application fell short. They were at

2312-452: The action, allowing a wide range of shotshells to be used, from standard to magnum loads, as long as they provide the minimum recoil level to compress the spring. Note that the shotgun must be free to recoil for this to work—the compressibility of the shooter's body is sufficient to allow this movement, but firing the shotgun from a secure position in a rest or with the stock against the ground will not allow it to recoil sufficiently to operate

2380-423: The barrel and bolt recoil together only a short distance before they unlock and separate. The barrel stops quickly, and the bolt continues rearward, compressing the recoil spring and performing the automated extraction and feeding process. During the last portion of its forward travel, the bolt locks into the barrel and pushes the barrel back into battery. The method of locking and unlocking the barrel differentiates

2448-409: The barrel backwards, in addition to the recoil energy. This boost provides higher rates of fire and/or more reliable operation. This type of mechanism is also found in some suppressors used on short recoil firearms, under the name gas assist or Nielsen device , where it is used to compensate for the extra mass the suppressor adds to the recoiling parts both by providing a boost and decoupling some of

2516-405: The bolt body is large enough for it to remain stationary while the recoiling gun and locked bolt head move rearward. This movement compresses the spring between the bolt head and bolt body, storing the energy required to cycle the action. Since the spring can only be compressed a certain amount, this limits the amount of force the spring can absorb, and provides an inherent level of self-regulation to

2584-412: The bolt carrier that are necessary for full-auto firing, such as the sear engagement surface, must be machined off during the semi-auto conversion process. Semi-auto RPD variants must also fire from a closed bolt, which requires the addition of a striker mechanism and other fire control group parts that are not found on full-auto RPD machine guns. Soviet engineers Science and technology in

2652-481: The bolt head, extracts and ejects the cartridge, cocks the hammer, and compresses the return spring. Once the bolt reaches the end of its travel, the return spring provides the force to chamber the next round from the magazine, and lock the bolt closed. Some short-recoil–operated firearms, such as the German MG 42 and MG 3 , use a mechanism at the muzzle to extract some energy from the escaping powder gases to push

2720-432: The clam-shell case has a notch from which the screwdriver end of the multi-tool can protrude. During its service life, the weapon was modernized several times. Initially, the gas block was modified as was the rear sight, where the windage adjustment knob for the rear sight was moved to the left side of the notch. Later, the RPD was modified with a non-reciprocating cocking mechanism with a folding charging handle (replacing

2788-413: The cutting edge of science in fields such as mathematics and in several branches of physical science , notably theoretical nuclear physics , chemistry, and astronomy . The physical chemist and physicist Nikolay Semenov was the first Soviet citizen to win a Nobel Prize , in 1956 among several other Soviet Nobel Prize winners and the mathematician Sergei Novikov was the first Soviet citizen to win

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2856-404: The early 1900s, a Swedish engineer who was awarded a number of patents for his inertia operated design between 1900 and 1908 and sold about 5,000 automatic shotguns using the system in 1908–1909. In a reversal of the other designs, some inertia systems use nearly the entire firearm as the recoiling component, with only the bolt remaining stationary during firing. Because of this, the inertia system

2924-495: The fact that the integrated disposable cartridge (both bullet and propellant in one easily interchangeable unit) made these designs viable. The earliest mention of recoil operation in the British patent literature is a patent by Joseph Whitworth filed in 1855 which proposed to use recoil to partially open the breech of a rifle, the breech then being manually pulled the rest of the way back by hand. Around this time, an American by

2992-405: The feeding of the RPD. The combined belt segments are stored in a metal drum that is attached to a mount on the receiver, for a total of 100 rounds. The RPD can also feed belts that are not contained in a drum if, for example, there is a need for more than 100 rounds of linked ammunition at a time. The feed system is operated by a roller connected to the reciprocating bolt carrier assembly. The belt

3060-407: The field would have been accomplished using the knob on the rear sight. A number of RPDs were fitted with a side rail (attached to the left side of the receiver) to accept an NSP-2 night vision sight . Standard accessories issued with the weapon include a sling , extra ammunition drums and belts (with either belt or shoulder pouches for same), oil bottle , cleaning rod (carried in a slot on

3128-474: The first man in space. The Soviets maintained a strong space program until economic problems led to cutbacks in the 1980s. The Soviet Union also had more scientists and engineers, relative to the world population, than any other major country due to the strong levels of state support for scientific developments by the 1980s. Although the sciences were less rigorously censored than other fields such as art, there were several examples of suppression of ideas . In

3196-460: The fixed charging handle connected to the bolt carrier) that does not move during firing. The feed port received a dust cover, which when open, serves as a feeding ramp for the ammunition belt. This version of the light machine gun was produced mainly in China and Poland. A further modified variant (sometimes referred to as the RPDM ) includes an extended gas cylinder and a recoil buffer mechanism in

3264-416: The following major groups: the receiver and barrel, bolt, bolt carrier, feed tray and feed cover, the recoil mechanism and the trigger group and stock. The RPD fires from an open bolt in full auto only. There is no provision for semi-auto fire , although RPD gunners were trained to fire in short bursts to prolong the life of the non-quick-change barrels. The RPD feeds ammunition from the left side using

3332-444: The fully automatic recoil operated machine gun. Furthermore, in 1875 a means of cocking a rifle through recoil was patented through the patent agent Frank Wirth by a German called Otto Emmerich. Finally came Maxim's 1883 automatic recoil operated machine gun which introduced the modern age of automatic machine guns. The same forces that cause the ejecta of a firearm (the projectile(s), propellant gas, wad, sabot , etc.) to move down

3400-464: The last link of the first belt and the first link of the next belt together. When the last round in a belt segment is fired, that belt segment disconnects and falls away, reducing the chances of the empty belt snagging or becoming entangled. Regardless of the style of belt used, the RPD was typically fed using 100 rounds of linked ammunition. The Russian, Hungarian, and Chinese RPD belts are all interchangeable, and can be linked together without affecting

3468-407: The left side of the receiver), (stowed in a compartment inside the stock), and drop case. The cleaning kit consists of a rectangular metal clam-shell case that typically contains the following tools and spare parts: pin punch (used for disassembling the bolt), cleaning jag, multi-tool (includes screwdriver, small and large wrenches used for adjusting the front sight and gas system, respectively, and

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3536-443: The mechanism. Likewise, care must be exercised when modifying weapons of this type (e.g. addition of extended magazines or ammunition storage on the stock), as any sizable increase in weapon mass can reduce the work done from recoil below that required to cycle the action. As the recoil spring returns to its uncompressed state, it pushes the bolt body backward with sufficient force to cycle the action. The bolt body unlocks and retracts

3604-419: The most notorious, agronomist Trofim Lysenko refused to accept the chromosome theory of heredity usually accepted by modern genetics . Claiming his theories corresponded to Marxism , he managed to talk Joseph Stalin in 1948 into banning the practice and teaching of population genetics and several other related fields of biological research; however, this decision was reversed in the 1960s. Cybernetics

3672-473: The name of Regulus Pilon is sometimes stated to have patented in Britain a gun that used a limited form of recoil operation. He had three British patents related to firearms around the 1850s to the 1860s; however, all of them refer to a means of dampening recoil in firearms, which wasn't a new idea at the time, rather than true recoil operation. The next to mention recoil operation in the British patent literature

3740-675: The party continued declaring various new theories "pseudo-scientific". Genetics , pedology and psychotechnics were already banned in 1936 by a special decree of the Central Committee . On August 7, 1948, the V.I. Lenin Academy of Agricultural Sciences announced that from that point on Lamarckian inheritance , the theory that personality traits acquired during life are passed on to offspring, would be taught as "the only correct theory". Soviet scientists were forced to redact prior work, and even after this ideology, known as Lysenkoism ,

3808-434: The resulting semi-auto rifle cannot be readily converted into a machine gun. Numerous machining operations are necessary to modify the de-milled full-auto RPD parts for use in a semi-auto RPD receiver. For example, the side rails on the bolt carrier must be machined to fit into the slots of the semi-auto receiver, which are purposefully made too narrow to accept an unmodified full-auto RPD bolt carrier. Additional portions of

3876-435: The scientific establishment to lose much of its funding and stability for the first time since the 1920s. Salaries were not paid for months, and research monies disappeared. International organizations offered aid programs to discourage emigration. In general, however, the Russian scientific community has been slow to recover from the political and economic shocks of the 1990s. The following Soviet scientists were recipients of

3944-631: The second nation to develop an atomic bomb , in 1949, four years after the United States . The Soviet Union detonated a hydrogen bomb in 1953, a mere ten months after the United States. Space exploration was also highly developed: in October 1957 the Soviet Union launched the first artificial satellite , Sputnik 1 , into orbit ; in April 1961 a Soviet cosmonaut , Yuri Gagarin , became

4012-417: The sides of the bolt, which are forced outwards (by the angled sides of the hammer) into recesses cut into the receiver body, after which firing occurs when the face of the hammer strikes the rear of the firing pin. The mechanism is simple, rugged and reliable. It features a trigger mechanism that is limited to fully automatic fire only. The bolt is equipped with a spring-loaded casing extraction system , and

4080-453: The sight into place. The rear sight is adjusted for elevation using a slider. The rear sight is marked in 100 meter increments from 100 to 1,000 meters. The rear sight is adjusted for windage using a knob on the left side of the rear sight. Because the front sight of the RPD must be partially disassembled in order to adjust windage, in practice the front sight would have been zeroed for windage and then locked in place. Adjustment for windage in

4148-482: The stock. Late production RPD variants also had the fixed drum attachment removed (instead, the ammunition container was "hung" from the feed port cover) and feature a folding cleaning rod, that is stored in the weapon's butt (in the Chinese Type 56-1 variant). American firearm manufacturer DS Arms makes a semi-auto variant for civil market and a full-auto variant for export, both in the original design and also in

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4216-405: The suppressor's mass from the firearm's recoiling parts. Muzzle boosters are also used on some recoil-operated firearms' blank-firing attachments to normalize the recoil force of a blank round (with no projectile) with the greater force of a live round, in order to allow the mechanism to cycle properly. Several revolvers use recoil to cock the hammer and advance the cylinder. In these designs,

4284-419: The system of specialized academies, or the research arms of various government ministries. The core of fundamental science was the USSR Academy of Sciences , originally set up in 1925 and moved from Leningrad to Moscow in 1934. It consisted of 250 research institutes and 60,500 full-time researchers in 1987, a large percentage in the natural sciences such as biology . All of the union's republics except

4352-402: The use of blank ammunition will typically cause the mechanism not to work correctly, unless a device is fitted to boost the recoil. Recoil-operated designs are broadly categorized by how the parts move under recoil. Long recoil operation is found primarily in shotguns , particularly ones based on John Browning 's Auto-5 action. In 1885 a locked breech, long recoil action was patented by

4420-711: The wide array of short recoil designs. Most common are the John Browning tilting barrel designs based on either the swinging link and locking lugs as used in the M1911 pistol or the linkless cam design used in the Hi Power and CZ 75 . Other designs are the locking block design found in the Walther P38 and Beretta 92 , rollers in the MG42 , or a rotating barrel used in the Beretta 8000 and others. An unusual variant

4488-498: Was also marginalised during the Stalinist period and received a hostile public campaign in 1951. Although, the discipline was rehabilitated during the post-Stalinist period from 1954 until 1959. Unlike some Western countries, most of the research work in the USSR was conducted not at universities, but at specially set up research institutes. The more prestigious of them were parts of the USSR Academy of Sciences ; others were within

4556-491: Was demonstrated to be false, it took many years for criticism of it to become acceptable. After the 1960s, during the Khrushchev Thaw , a policy of liberalization of science was implemented, but the policy of Lysenkoism continued. Lysenkoism was officially renounced in 1964, after Leonid Brezhnev came to power. After the collapse of the Soviet Union in 1991, rapid inflation and decline in governmental revenues caused

4624-554: Was organized under the aegis of the All-Union Academy of Agricultural Sciences of the Soviet Union . A large part of research was conducted in NII s — "scientific research institutes " ( Russian : НИИ, нау́чно-иссле́довательский институ́т ). There have been a great number of NIIs, each specialized in a particular field. Already in the 1920s, certain fields of scientific research were labeled "bourgeois" and "idealist" by

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