View source for ShKAS machine gun

{{Short description|Soviet aircraft machine gun}}
{{More footnotes|date=June 2013}}
{{Infobox weapon
|name= ShKAS machine gun
| image= ShKAS machine gun.jpg
| image_size = 300
|caption= A ShKAS at the [[Zadorozhny Equipment Museum]]
|origin= Soviet Union
|type= Aircraft [[machine gun]]
<!-- Type selection -->
|is_ranged=yes
<!-- Service history -->
|service=
|used_by= See [[#Users|''Users'']]
|wars= {{plainlist|
* [[World War II]]
* [[Spanish Civil War]]
* [[Second Sino-Japanese War]]
}}
<!-- Production history -->
|designer= {{plainlist|
* [[Boris Shpitalniy]]
* [[Irinarkh Komaritsky]]
}}
|design_date=1932
|manufacturer=
|unit_cost=
|production_date=1933–1945
|number= ~150,000
|variants=
<!-- General specifications -->
|weight= {{convert|9.8|kg|lb|abbr=on|1}} (wing-mounted)<br>{{convert|10.6|kg|lb|abbr=on|1}} (flexible)<br>{{convert|11.1|kg|lb|abbr=on|1}} (synchronized)<br>{{convert|10.2|kg|lb|abbr=on|1}} (1941 model, wing-mounted)
|length=
{{convert|935|mm|in|abbr=on|1}} (wing-mounted)<br>{{convert|955|mm|in|abbr=on|1}} (flexible role)<br>{{convert|1,077-1097|mm|in|abbr=on|1}} (synchronized)<br>{{convert|1,005|mm|in|abbr=on|1}} (1941 model)
|part_length=
{{convert|605|mm|in|abbr=on|1}} (wing and flexible)<br>{{convert|750|mm|in|abbr=on|1}} (synchronized)<br>{{convert|675|mm|in|abbr=on|1}} (1941 model)
|width=
<!-- Ranged weapon specifications -->
|caliber= 7.62 mm
|cartridge= [[7.62×54mmR]]
|action= [[Gas-operated reloading|Gas]]  with rotary feeding mechanism <ref>{{Cite web|url=http://www.forgottenweapons.com/russian-shkas-aerial-gun/|title=Russian ShKAS Aerial Gun|date=9 January 2013}}</ref>
|rate= {{plainlist|
* 1800 RPM (ShKAS)
* 1650 RPM ([[Synchronization gear|synchronized]])
* 3000 RPM (UltraShKAS)
}}
|velocity={{convert|775|-|825|m/s|ft/s|abbr=on}}
|range=
|max_range=
|feed= [[Belt (firearms)|Belt-fed]]
|sights= [[Iron sights]]
}}

The '''ShKAS''' ('''Sh'''pitalny-'''K'''omaritski '''A'''viatsionny '''S'''korostrelny, '''Shpitalny-Komaritski rapid fire for aircraft'''; [[Russian language|Russian:]] ШКАС - Шпитального-Комарицкого Авиационный Скорострельный) is a [[7.62 mm calibre]] [[machine gun]] widely used by [[Soviet Union|Soviet]] aircraft in the 1930s and during [[World War II]]. The ShKAS had the highest rate of fire of any aircraft machine gun in general service during WWII. It was designed by [[Boris Shpitalniy]] and [[Irinarkh Komaritsky]] and entered production in 1934. ShKAS was used in the majority of Soviet [[Fighter aircraft|fighters]] and [[bomber]]s and served as the basis for the [[ShVAK]] cannon.

== Description ==
ShKAS is a [[gas-operated]] aircraft [[machine gun]]; it has a single [[Chamber (firearms)|chamber]] in which the pin strikes the primer.

A key element of the ShKAS' high rate of fire is the revolving drum (feed cage) that holds ten rounds and provides a very smooth, progressive removal of the cartridges from their disintegrating link [[Belt (firearm)|belt]].

The bolt locking action is Browning-style, i.e. slightly tilted wedge bolt.

The bolt action mechanism is the "gas piston in a tube - rod - bolt frame", rather similar to Kalashnikov's assault rifle.

The main difference with AK is that, with AK, the whole assembly of piston-rod-bolt frame is a single large and heavy part. And, with ShKAS, it is split to several parts - the piston, the rod and the bolt frame, with a "personal" recoil spring for each of them (the weapon has a lot of springs in it).

This provided for the lightweight recoiling portion of the gun, which weighs only 921 grams (2.07&nbsp;lb).

[[File:Diagram of the ShKAS feed system operation - en.svg|thumb|Diagram of the ShKAS feed system operation.]]

A declassified US analysis of the feed system, based on models captured during the [[Korean War]], reads:<ref name="Chinn, pp. 78-79">Chinn, pp. 78–79</ref>
{{quote|An interesting departure was made from the heretofore orthodox practice of feeding ammunition to a gun of this caliber. The feed, somewhat resembling a grooved revolver cylinder, is an integral part of the gun, and the cartridges remain axial throughout the entire operation.

The cylindrical feed cage is rotated by an arm that engages a slot in the gas piston. A helical groove in the drum arrangement withdraws the cartridges from the metal disintegrating link belt as it moves through the feedway by engaging their rims and gradually camming the cartridges rearward. The freed cartridges are then presented at the bottom of the receiver for chambering by final rotation.

This circular type of feed holds ten rounds. Several phases are required to completely delink a round and roll it up into position for being shoved into the chamber. A small folding handle held on the top side is used to rotate the feed drum when filling with cartridges.

Camming the round slowly out of the belt with this type of feeder causes practically no drag when the weapon is fired at high speed. It has belt pull enough to take care of practically any length belt desired. [...]

The Russian Air Force nicknamed this circular arrangement the "bird-cage" feed. It is an adaptation of a system first used by the Polish designer, [[Gabriel Szakats]].}}
([[Ian V. Hogg]] called the ShKAS feeding system a "[[hamster wheel|squirrel cage]]".<ref name="Hogg1978">{{cite book|author=Ian V. Hogg|title=The illustrated encyclopaedia of firearms|year=1978|publisher=New Burlington Books|isbn=978-0-906286-41-8|page=[https://archive.org/details/illustratedencyc00hog_tda/page/279 279]|url-access=registration|url=https://archive.org/details/illustratedencyc00hog_tda/page/279}}</ref>)

After analysing the less unusual parts of the ShKAS, the US source concludes:<ref name="Chinn, pp. 78-79"/>
{{quote|Thus the Shkas is an innovation based on the features of the [[Maxim gun|Maxim]] (ejection and buffer), the Szakats (rotating feed), and the [[André Virgile Paul Marie Berthier|Berthier]] (piston-actuated, propped breech, locking.)}}

Although ShKAS is best known for its high rate of fire, it did have provision for slower cyclic rates by lowering the gas-pressure. This was done by "changing the position of the holes in the gas regulator, which comes with holes of three different sizes: 2.1 mm (1/12-inch), 2.5 mm (1/10-inch) and 3.2 mm (1/8-inch). The smaller the orifice used, the more moderate is the rate of fire obtained."<ref>Chinn, p. 80</ref>

== Variants ==
[[File:ShKAS tourelle.jpg|thumb|ShKAS in a ring mount]]
Initial production consisted of cable-charged wing-mounted and turret-mounted ShKAS with a synchronized version entering service in 1936.

By 1952 Western intelligence had identified five different models, all including the number "426" in their markings:<ref name="Chinn, p. 72">Chinn, p. 72</ref>
* a prototype "426" appeared in 1932
* KM-33, in flexible role, appeared in 1933
* KM-35, in flexible role (1934) and wing-mounted (1935)
* KM-36, in flexible role (1935) and propeller-synchronized (1937); the latter had an extra-long barrel
* a 1941 model, wing-mounted

"KM" stands for "constructed model", i.e. production. The intended role was marked with the letters "T" for flexible, "K" for wing, and "S" synchronized.<ref name="Chinn, p. 72"/> The flexible version was usually mounted in a Soviet copy of the [[Scarff ring]].<ref name="Chinn, p. 73">Chinn, p. 73</ref> The 1937 model had slightly higher maximum rate of fire of 2,000 rounds per minute.<ref name="Chinn, p. 73"/> The amount of ammunition normally carried was 750 rounds for the fixed models and 1,000 to 1,500 for the flexible.<ref>Chinn, p. 79</ref>

Soviet archives indicate the following production volumes, by year:<ref>Shirokorad, p. 73; there is no number given for 1936, 1939 and 1941–1942</ref>
* 1933 — 365 produced
* 1934 — 2,476
* 1935 — 3,566
* 1937 — 13,005
* 1938 — 19,687
* 1940 — 34,233
* 1943 — 29,450
* 1944 — 36,255
* 1945 — 12,455
In 1939, a small number of Ultra-ShKAS were produced featuring a firing rate of 3,000 rounds per minute but these saw only limited use due to reliability problems.

== Effectiveness ==
The ShKAS was the fastest-firing rifle calibre aircraft armament in general service in World War II. A one-second burst from the four ShKAS of a [[Polikarpov I-153]] or [[Polikarpov I-16]] placed 120 bullets within 15 [[angular mil]]s at 400 meters (1,312 feet) giving a firing density of 5 bullets per square meter of the sky. Moreover, the ShKAS was unusually light as well; the four guns, with 650 rounds of ammunition each, weighed a total of only 160&nbsp;kg (350&nbsp;lb).
ShKAS wasn't problem-free though. Soviet machine-gun technician Viktor M. Sinaisky recalled:

{{quote|The ShKAS machine gun had a high rate of fire but it also had 48 ways of jamming. Some of them could be fixed immediately, some could not. And 1,800 rounds a minute was an insanely high rate of fire. If you pulled the trigger too long, the ShKAS would fire all its ammo in one go and that would be it!!<ref name= "Drabkin pp. 60-68.">Drabkin 2007, pp. 60–68.</ref>}}

== Gun specifications ==
* [[Cartridge (firearms)|Cartridge]]: [[7.62×54mmR]]
* [[Caliber|Calibre]]: {{convert|7.62|mm|in|abbr=on|3}}
* [[Rate of fire]]: 1,800 rounds/min wing- or turret-mounted; 1,625 rounds/min synchronized. UltraShKAS: 3,000 rounds/min.
* [[Muzzle velocity]]: {{convert|825|m/s|ft/s|abbr=on}}
* [[Weight]]: {{convert|10|kg|lb|abbr=on}} empty; {{convert|40|kg|lb|abbr=on}} with 650 rounds of ammunition.

== 7.62 mm ammunition specifications ==
Although chambered in the 7.62×54mmR, the ShKAS guns used cartridges specially built for them to [[Engineering tolerance|smaller tolerances]]; to distinguish them from the regular 7.62 ammunition, the [[Russian alphabet|Cyrillic]] letter "Sh" ([[Ш]]) was imprinted on the bottom of the cases. The cases, designed by N. M. Elizarov, also had a few additional features like double crimping and a thicker case wall of "bimetallic" construction instead of the traditional [[brass]].<ref>Сергей МОНЕТЧИКОВ, [http://www.bratishka.ru/archiv/2012/01/2012_1_7.php ОРУЖЕЙНАЯ МАСТЕРСКАЯ: 7,62-мм ВИНТОВОЧНО-ПУЛЕМЕТНЫЕ ПАТРОНЫ] {{Webarchive|url=https://web.archive.org/web/20180330012655/http://www.bratishka.ru/archiv/2012/01/2012_1_7.php |date=2018-03-30 }}, ''Bratishka'' 2012/1</ref> The main type of bullet used was [[armour-piercing incendiary]] B-32 bullet. Ammunition marked as such should not be fired out of any regular 7.62×54mmR rifles.<ref>{{Cite web|url=http://7.62x54r.net/MosinID/MosinAmmoID01.htm|title=Russian & Soviet 7.62x54r}}</ref>
* Bullet weight: 148 [[grain (measure)|grains]] (9.6 grams)
* Round weight: 370 [[grain (measure)|grains]] (24 grams)
* [[Ballistic coefficient]]: 2,100&nbsp;kg/m<sup>2</sup> (3.0&nbsp;lb/in<sup>2</sup>)
* [[Tracer ammunition]] duration: 750 m (2,460&nbsp;ft)
* Armour piercing: 11&nbsp;mm (0.43&nbsp;in) at 400 m (1,312&nbsp;ft)

== Possible influences ==
Some military historians believe the feed system of the [[Mauser MG 213|Mauser 213C]] (the seminal [[revolver cannon]] for Western designs) was inspired by the ShKAS.<ref>[[George M. Chinn|George Chinn]] 1951, The Machine Gun: Development During World War II and Korean Conflict by the United States and their Allies of Full Automatic Machine Gun Systems and High Rate of Fire Power Driven Cannon, Volume III, Parts VIII and IX. p. 44</ref><ref name="Gunston1987">{{cite book|author=Bill Gunston|title=The Illustrated Encyclopedia of Aircraft Armament: A Major Directory of Guns, Rockets, Missiles, Bombs, Torpedoes and Mines|year=1987|publisher=Salamander Books|isbn=978-0-86101-314-2|page=24}}</ref><ref name="Hoffschmidt1969">{{cite book|author=E. J. Hoffschmidt|title=German aircraft guns and cannons|year=1969|publisher=WE, inc.|page=117}}</ref> However, the method of operation is very different: gas-operation on the ShKAS versus a revolving cam on the MG 213C.

== Users ==
* {{flagcountry|Soviet Union}}
* {{flagicon|Spain|1931}} [[Second Spanish Republic]]
* {{ROC}}
* {{flagcountry|Yugoslavia}}

==See also==
* [[MG 81 machine gun]]
* [[Savin-Narov machine gun]]
* [[SIBEMAS]] machine gun
* [[Vickers K machine gun]]
* [[Revolver cannon]]
* [[List of firearms]]
* [[List of Russian weaponry]]
* [[List of common World War II infantry weapons|List of common World War II weapons]]

==References==
;Notes
{{Reflist}}

;Bibliography
{{refbegin}}
*  Drabkin, Artem. ''The Red Air Force at War: Barbarossa and the Retreat to Moscow – Recollections of Fighter Pilots on the Eastern Front''. Barnsley, South Yorkshire, UK: Pen & Sword Military, 2007. {{ISBN|1-84415-563-3}}.
* Романов Д. И. Оружие Воздушного Боя (Romanov D.I., ''Aerial Weapons'')
* Chinn, George M. The Machine Gun, Vol II, Part VII. US Department of the Navy, 1952
* Широкорад А.Б. (2001) ''История авиационного вооружения'' Харвест (Shirokorad A.B. (2001) ''Istorya aviatsionnogo vooruzhenia'' Harvest. {{ISBN|985-433-695-6}}) (''History of aircraft armament'')
{{refend}}

==External links==
{{Commons category|ShKAS}}
* [http://users.telenet.be/Emmanuel.Gustin/volume1/ultrashkas.jpg Ultra-ShKAS photo]
* [http://www.kalashnikov.ru/upload/medialibrary/300/32_37.pdf патроны для сверх пулемета]

{{Russian and Soviet Aircraft Ordnance}}

[[Category:Medium machine guns]]
[[Category:World War II machine guns]]
[[Category:7.62×54mmR machine guns]]
[[Category:Machine guns of the Soviet Union]]
[[Category:Cold War firearms of the Soviet Union]]
[[Category:Aircraft guns of the Soviet Union]]
[[Category:KBP Instrument Design Bureau products]]
[[Category:Military equipment introduced in the 1930s]]