ShVAK cannon

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

The ShVAK was a Soviet 20 mm autocannon used in World War II. It was designed by Boris Shpitalniy and Semyon Vladimirov, developed between 1935 and 1936, and produced from 1936 to 1946. The gun was gas-operated and belt-fed, with a “bird-cage” feed system that kept rounds de-linked and smoothly fed. It fired 20×99 mm rounds at about 700–800 rounds per minute, with a muzzle velocity around 750–790 m/s. The 20 mm version used a blast-reduction tube at the barrel end to minimize blast effects on aircraft.

Three main aircraft-mounted variants existed: SP (synchronized firing), MP (wing-mounted), and KP (wing-mounted with a different mounting). Length and weight varied by variant: SP/MP about 2,122 mm long and 44.5 kg; KP about 1,679 mm long and 40 kg; and TP (for flexible mounts) about 1,726 mm long and 42 kg. The 20 mm guns ran on a 20×99 mm cartridge; there was also an early 12.7 mm ShVAK version, but only a few were produced and it was soon superseded.

Key design features included a gas regulator with four holes to adjust fire rate, and a barrel end threaded to accept a blast-reduction tube. The gun’s feed cage and redesigned gas system helped reduce jamming and blowback during high-rate firing.

The ShVAK saw widespread use on Soviet fighters and bombers of the era, including the I-16, I-153, MiG-3, Yak-1/3/7/9, LaGG-3, La-5/7, Pe-3, and Soviet-modified Hawker Hurricanes. It was also installed on the Tu-2 and Pe-2 bombers, and on Il-2s in early versions. A tank version, the TNSh, was mounted on light tanks such as the T-38 and T-60, while flexible mounts equipped other bombers like the Pe-8 and Yer-2.

Ammunition mixed fragmentation-incendiary and armor-piercing-incendiary rounds, with projectiles featuring a hardened steel core and incendiary fillers. Early issues with premature cook-off were addressed by fuse changes (MG-3 to MG-201, then K-6) by 1938.

After World War II, the 20 mm ShVAK was largely replaced by the lighter Berezin B-20. The 12.7 mm version had limited production and did not become widespread. The ShVAK was noted by Western intelligence as very light and compact for its power, though it was more challenging to manufacture due to its non-heat-treated parts.