ShKAS is a gas-operated revolver-type machine gun; it has a single chamber in which the pin strikes the primer. A key element of the ShKAS' high rate of fire is the revolving drum that holds ten rounds and provides a very smooth, progressive removal of the cartridges from their disintegrating linkbelt. Another element is the lightweight recoiling portion of the gun, which weighs only 921 grams. A declassified US analysis of the feed system, based on models captured during the Korean War, reads: After analysing the less unusual parts of the ShKAS, the US source concludes: 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, 2.5 mm and 3.2 mm. The smaller the orifice used, the more moderate is the rate of fire obtained."
Variants
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:
KM-36, in flexible role and propeller-synchronized ; 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. The flexible version was usually mounted in a Soviet copy of the Scarff ring. The 1937 model had slightly higher maximum rate of fire of 2,000 rounds per minute. The amount of ammunition normally carried was 750 rounds for the fixed models and 1,000 to 1,500 for the flexible. Soviet archives indicate the following production volumes, by year:
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
Ultra-ShKAS: 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 mils at 400 meters 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 kg. ShKAS wasn't problem-free though. Soviet machine-gun technician Viktor M. Sinaisky recalled:
Gun specifications
Cartridge: 7.62×54mmR
Calibre:
Rate of fire: 1,800 rounds/min wing- or turret-mounted; 1,625 rounds/min synchronized. UltraShKAS: 3,000 rounds/min.
Muzzle velocity:
Weight: empty; 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 smaller tolerances; to distinguish them from the regular 7.62 ammunition, the Cyrillic letter "Sh" 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. The main type of bullet used was armour-piercing incendiary B-32 bullet.
Some military historians believe the feed system of the Mauser 213C was inspired by the ShKAS. However, the method of operation is very different: gas-operation on the ShKAS versus a revolving cam on the MG 213C.
