ShVAK cannon The ShVAK ( , " Shpitalny - Vladimirov large - calibre for aircraft " ) was a 20 mm autocannon used by the Soviet Union during World War II . It was designed by Boris Shpitalniy and Semyon Vladimirov and entered production in 1936 . ShVAK were installed in many models of Soviet aircraft . The TNSh was a version of the gun produced for light tanks ( ) . Development and production . 12 . 7 mm ShVAK . The development of the 12 . 7 mm ShVAK was in response to a Soviet government decree passed on 9 February 1931 , directing domestic manufacturers to produce an aircraft machine gun for the 12 . 7×108mm cartridge that had been introduced a couple of years before for the DK machine gun . Tula designer S . V . Vladimirov answered the call by producing basically an enlarged version of the ShKAS , with a 1246 mm long barrel and a total length of 1726 mm . The first prototype was ready for trials on May 28 , 1932 . The testing process was fairly drawn out , but the 12 . 7 mm ShVAK was nominally adopted into service in 1934 . Series production officially started in 1935 at the INZ - 2 factory in Kovrov , but production soon fell well behind schedule because the ShVAK receiver was fairly complex to manufacture . According to Soviet records , out of the 410 12 . 7 mm ShVAKs planned for aircraft in 1935 , only 86 were completed ; for the tank version , 40 had been planned but only 6 were delivered that same year . A 1952 Western intelligence report indicates that only " a few " ShVAKs were produced in the 12 . 7 mm caliber . A further problem complicating the adoption of the gun was that the 12 . 7 mm ShVAK ended up not using the 12 . 7×108mm rimless cartridge used by the DS machine gun , but rather — because it was an adaptation of the ShKAS mechanism — it required its own rimmed 12 . 7 mm cases . Production of the rimmed 12 . 7 mm ammunition ceased in 1939 , when it was decided that the Berezin UB was preferable because it could share ammunition with the DShK . 20 mm ShVAK . The 20 mm ShVAK was designed sometime between 1935 and 1936 and series production began in 1936 . A few months later , production of the 12 . 7 mm version ceased . Similarly to its predecessors , the 20 mm ShVAK was a gas - operated gun , belt - fed by disintegrating link ammunition . Depending on the intended mount , the ShVAKs were marked with " MP " for the tank version ( total gun length 2122 mm ; weight 44 . 5 Kg ) , " KP " for the wing - mounted version ( 1679 mm total length ; 40 Kg ) , " TP " for flexible mounts ( 1726 mm length ; 42 Kg ) , and " SP " for synchronized installations . The " bird - cage " feed system in the 20 mm ShVAK was an improved version of the ShKAS . It could hold 11 rounds and had an even smoother operation . As with the ShKAS , the purpose of the feed cage was to gradually delink the rounds , avoiding any belt lurch . The Berthier - type gas regulator had four holes ( of 3 . 5 , 4 , 4 . 5 , and 6 mm ) allowing for different rates of fire to be selected . The most significant design difference from the ShKAS was that the gas cylinder was moved under the barrel in the ShVAK , giving it a more compact assembly . The end of the barrel was threaded , and this thread was used to screw on a blast - reduction tube of a length that depended on the installation requirements : The 1952 Western intelligence report concluded that the 20 mm ShVAK was " in relation to its power , the gun is very light and extremely compact " and that it " has a range comparable to our M3 cannon , although their short barrel version is 16 pounds lighter " . It was however considered " relatively difficult to produce " in American factories , because it was constructed from relatively soft parts ( not heat - treated ) that were then filed down . This choice of materials was assumed motivated by the desire to allow parts to " deform and bend well in advance of fracture " enabling a safer operation at a high rate of fire , but having the tradeoff of shorter overall lifespan of the gun . Soviet archives indicate the 20 - mm ShVAK was produced in large numbers during World War II : After the war , the ShVAK was supplanted by the Berezin B - 20 , which offered similar performance but weighed significantly less . Installations . Three Polikarpov I - 16 aircraft , all produced in January 1939 , were armed with the propeller - synchronized version of the 12 . 7 mm ShVAK ; this short series was given the I - 16 Type 16 designation . The three fighter planes successfully passed the factory trials and were delivered to the VVS for military trials . The cancelled Yatsenko I - 28 was also planned to use the 12 . 7 mm ShVAK in a synchronized pair , but the few prototypes which flew in the summer of 1939 did so without armament because a synchronizer for their engine had not been developed . The 20 mm ShVAK was installed in wing or synchronized mounts in the following fighters : Polikarpov I - 153 P and I - 16 , Yakovlev Yak - 1 , Yakovlev Yak - 3 , Yakovlev Yak - 7 B , LaGG - 3 , Lavochkin La - 5 and La - 7 , the Petlyakov Pe - 3 night fighter and on Soviet - modified Hawker Hurricane aircraft . It was also installed on the wings of the Tupolev Tu - 2 bomber and some ground attack versions of the Petlyakov Pe - 2 bomber also had it installed in a fixed mounting . Some early versions of the Ilyushin Il - 2 ground attack aircraft also carried it , but superseded in that aircraft by the 23 mm Volkov - Yartsev VYa - 23 . The flexible - mount ShVAK was used in the Petlyakov Pe - 8 and Yermolayev Yer - 2 bombers . The tank version was installed on the T - 38 and T - 60 light tanks . Ammunition . ShVAK ammunition consisted of a mix of fragmentation - incendiary and armor piercing - incendiary rounds . There were problems with ammunition development as well . There were cases of premature cook - off of the ammunition in the barrel . The problem was first addressed in 1936 by changing the fuse from the MG - 3 model to the MG - 201 model , but the problem was not completely eliminated until the introduction of the K - 6 fuse in 1938 , which reliably prevented projectiles from arming until they were 30 to 50 cm out of the barrel .