Nudelman - Suranov NS - 45 The Nudelman - Suranov NS - 45 was an enlarged version of the Soviet Nudelman - Suranov NS - 37 aircraft autocannon . It was evaluated for service on 44 Yakovlev Yak - 9 K aircraft during World War II , but proved to stress the airframes too much . The NS - 45 was also mounted on the prototype Tupolev Tu - 1 night fighter after the end of World War II . Design and development . The NS - 45 was created as a result of a July 1943 decision of the State Defense Committee to arm Soviet fighters with 45 mm autocannons . As with the 37 mm autocannons already installed in some Soviet and lend - lease single - engine fighters , the intended method of installation of the 45 mm gun was to have its barrel pass through the engine block and the empty propeller shaft , in this case that of the Yak - 9 . Consequently , the main difficulty in designing the 45 mm autocannon was the limitation imposed by the engine blocks available for this aircraft . Accounting for the diameter of the 45 mm shell , the Yak - 9 engine blocks only allowed a wall thickness of 4 mm for the new gun ' s barrel , which was almost half the thickness of the barrel wall of the NS - 37 . ( Another source gives 55 mm as the diameter of opening in the engine reducer shaft , resulting in a wall thickness of 3 . 75 mm for the NS - 45 barrel relative to 7 . 1 mm for the NS - 37 barrel , both measured at the this spot which was approximately 61 cm away from the muzzle . ) The decision of the Defense Committee was followed by a short design competition between Soviet designs bureaus OKB - 15 and OKB - 16 . The former proposed an enlarged version of their unreliable Shpitalny Sh - 37 ; although they made a prototype that passed factory tests in a LaGG - 3 , their 45 mm gun was not accepted for state trials because of the known issues with the Sh - 37 design . OKB - 16 presented an enlarged version of their successful NS - 37 . The recoil force of the NS - 45 peaked at seven tons , a force roughly 40 % greater than that experienced with the NS - 37 ( about 5 . 5 tons ) . Consequently , the NS - 45 was fitted with a muzzle brake — a first in Soviet aircraft - gun design . Concomitantly with the gun design , a new cartridge was developed using the standard 45 mm fragmentation shell of the 21 - K anti - aircraft gun . ( This projectile had a tracer that burned for eleven seconds and was fitted with the MG - 8 contact fuse . ) The total length of the new cartridge was limited to the same value as for the NS - 37 ammunition — 328mm . In order to accommodate the larger shell , the case body ( brass ) was necked up and also slightly reduced in length from 195 mm of the NS - 37 ammunition to 185 mm . The resulting 45 mm cartridge weighted 1 . 93 kg , of which 1 . 065 kg was the weight of its shell . The muzzle velocity of the NS - 45 was 780 m / s and its rate of fire was around 260 - 280 rounds per minute . Production and service . The NS - 45 was built in small numbers at Factory Number 74 in the last two years of the war ; 75 exemplars were made in 1944 and 120 were made in 1945 . Yak - 9K . In fighters , the NS - 45 gun was first installed on a modified Yak - 9T , which was normally armed with a NS - 37 gun . This aircraft , with constructor number 0121 , effectively became the first Yak - 9K prototype . The " K " suffix stood for " Krupnokalibernyi " , meaning large caliber . The protruding barrel and muzzle brake of the NS - 45 made the Yak - 9K some 20 cm longer than the Yak - 9T . The NS - 45 was supplied with 29 rounds of ammunition in the Yak - 9K , which were fed using a belt . The only other armament installed on the Yak - 9K was a UBS ( a propeller - synchronized 12 . 7 mm machine gun ) supplied with 200 rounds of ammunition . The theoretical weight of fire of the Yak - 9K was 5 . 53 kg / s ( 12 . 2 lb / s ) , which gave it a considerable advantage in this department relative to most single - engine German aircraft of the time except the " flying gun - batteries " such as the Fw 190 A - 6 / R1 or the Bf 109 G - 6 / R6 . Compared to these , the Yak - 9K maintained however good horizontal maneuverability because its wings were not loaded with armament . Developed in late 1943 , the Yak - 9K prototype was tested at the Central Research Institute of the Soviet Air Force ( VVS NII ) between January 12 and April 8 , 1944 . Between April and June 1944 a limited production run of this aircraft was manufactured at a plant in Novosibirsk and delivered for military trials to the 3rd Fighter Air Corps . For military ( combat ) trials 44 Yak - 9Ks of this limited production run were used . These trials took place between 13 August and 18 September 1944 at the 3rd Belorussian Front , and from 15 January 1945 to 15 February 1945 at the 2nd Belorussian Front . The Soviet Air Forces units involved were the 274th Fighter Aviation Regiment ( IAP ) of the 278th Fighter Aviation Division ( IAD ) and the 812nd IAP of the 65th IAD . Twelve German aircraft were claimed by Yak - 9K fighters , with an average expenditure of ten rounds per target . Of these twelve German aircraft claimed by Yak - 9K pilots , eight were Fw 190 and four were Bf 109G . Combat experience with the Yak - 9K showed that although the NS - 45 cannon proved deadly to enemy aircraft , realistically only its first shot could be aimed . A three - round burst , even when fired near the maximum airspeed of the Yak - 9K , resulted in a noticeable loss of both airspeed and stability of the aircraft . Sometimes oil and water lines sprung leaks after the gun was fired . Firing the NS - 45 at airspeeds below 350 km / h even shook the pilot back and forth as if in an automobile suddenly decelerating and accelerating . Another issue affecting the effectiveness of the Yak - 9K was that it had a poorer power to weight ratio compared to its proximate predecessor , although this was mostly due to its larger fuel tanks rather than the weight of the armament ; its fuel tanks had been enlarged from the 440 - liter tanks of Yak - 9T to 650 - liter tanks , allowing it to carry an additional 153 kg of gasoline . The loss of airspeed relative to the Yak - 9K was about 40 km / h at 5 , 000 m , and climbing to this altitude took about a minute longer with the Yak - 9K . In an attempt to address this problem , some of the Yak - 9K already in service were retrofitted with smaller 480 - liter tanks . To compensate for the Yak - 9K ' s poor maneuverability in the vertical plane , pilots of the 812th IAP developed tactics that essentially employed the aircraft as a heavy fighter , using it for surprise attacks on bombers , and providing it with an escort by nimbler Yak - 3 s flying top cover . Ultimately , it was decided that the Yak - 9K would not go into mass production . Besides the reliability and airframe performance issues , another contributory reason was that the German bombers still active on the Eastern front at this point in the war were mainly Fw 190 " Jabo " , and the 45 mm shell was overkill for these . A total of 53 Yak - 9Ks had been built by then . Other aircraft . The NS - 45 was also tried on an Ilyushin Il - 2 , with one gun mounted in each wing , but the design was not put into series production . On August 20 , 1943 , the People ' s Commissariat of Aviation Industry of the USSR ordered that an Il - 2 be tested with the new 45 mm aircraft guns . An Il - 2 exemplar fitted with the new guns had been manufactured by September 10 , 1943 , when it was sent to the VVS NII for trials . Due to various issues which arose integrating the NS - 45 gun with this aircraft , testing was delayed until February 8 , 1944 . The results were disappointing ; the Il - 2 - mounted NS - 45s exhibited poor accuracy hitting tank - size targets and their recoil was almost twice what the Il - 2 ' s wings could safely handle ( about 4000 tons - force ) . One of the three versions of the prototype ground attack ( shturmovik ) Tu - 2 Sh was equipped with two NS - 37s and two NS - 45s as frontal armament . This variant was tested sometime in 1946 . A more substantial test program took place between 30 December 1946 and 3 October 1947 with the Tupolev Tu - 1 night fighter prototype , which was fitted with two NS - 45s in the nose — each one supplied with 50 rounds — and with two NS - 23 s in the wing roots . The Tu - 1 was abandoned because of its unreliable engines .