I have a question WHERE did such a breakthrough in the NS-37 come from, because A.B. Shirokorad writes in ““HISTORY OF AVIATION WEAPONS”” (in Russian) this data
NS-37 37mm Aircraft Cannon
In April 1941, engineers Nudelman and Suranov of OKB-16 began designing the 37mm 11-P cannon. The project was approved on June 15, 1941.
The cannon’s automatic mechanism operated through the recoil energy of the barrel with a short recoil action. The barrel’s bore was locked by a longitudinally sliding piston-type bolt. A cam-type accelerator was attached to the fixed part of the mechanism.
After each burst, the striker, bolt, and cartridge would stop at the sear in the farthest rear position, which prevented the cartridge from igniting due to the heat generated during firing.
Continuous feeding of the cannon with shells was achieved by a metal link belt from a cartridge box. The amount of ammunition depended solely on the box size and the method of belt placement.
The cannon’s recoil system consisted of a recoil brake and a counter-recoil brake. The reliability and fault-free operation of this system were ensured by the forced feeding and chambering of shells and the forced extraction and removal of fired casings.
However, the mechanism had a peak-like recoil force. For a 37mm cannon, the average recoil force was around 2230 kg, but upon striking the buffer, it reached 7500 kg. The recoil was significant at both the end of the barrel’s travel and the end of the bolt’s travel.
When firing from a Yak-9 at speeds up to 350 km/h, the aircraft would significantly shake, and accurate fire was only possible with the first shot, with subsequent rounds scattering.
The length of the NS-37 cannon’s barrel was 2300 mm. Its overall dimensions were 3400 mm in length, 215 mm in width, and 415 mm in height. The weight of the motorized version was 171 kg, while the wing-mounted version weighed 160 kg. The rate of fire was 240-260 rounds per minute. The cannon was capable of continuous fire within its ammo capacity.
The NS-37 cannon’s ammunition included BZT and OZT shells. The OZT shell weighed 732 g and contained 34 g of powerful explosive substance A-IX-2. The shell featured a time-delay fuse (MG-7 or MG-8 initially, later A-37) and an auto-detonator with a 9-12 second delay. The initial velocity of the OZT shell was 865 m/s.
When hitting a 1-1.5mm duralumin surface, the OZT shell created a hole of 0.46 m in diameter at the entry point and 0.78 m at the exit point.
The BZT shell weighed 770 g with an initial velocity of 810 m/s.
At a distance of 200 m, it could penetrate 50mm of armor when fired perpendicular to the target, or 30mm of armor at a 45° angle.
At 400 m, the BZT shell could penetrate 45mm of armor perpendicularly or 40mm at a 30° angle.
Both shells had a similar propellant charge of about 210 g. The weight of the shell casing was 607 g, and the link weighed 160 g.
The first experimental 11-P cannon was completed on July 27, 1941. In August 1941, the experimental model underwent adjustments and factory tests. In early October 1941, the cannon was mounted on a LaGG-3 fighter for state trials, which concluded in March 1942.
On March 30, 1942, the Air Force decided to conduct repeated flight tests of the 11-P cannon. At the same time, the task was set to modify the cannon for a shell with a rimless casing, i.e., for the LU-37 cartridge. The design was revised over three months, and a new version was built for the Sh-37 cartridge.
This new model was tested on the same LaGG-3 fighter, and from July 21 to August 17, 1942, the state trials were repeated.
Field tests of the 11-P cannon were conducted on the LaGG-3 from April 21 to June 7, 1943, on the Kalinin front, and on the Yak-9T from July 22 to August 21, 1943, on the Central front. After the field trials, the cannon was adopted into service under the NS-37 designation.
The Yak-9T (tank killer version) was produced from March 1943 to June 1945, with a total of 2748 units built.
In March-April 1943, two NS-37 cannons were mounted on a two-seat IL-2 with an AM-38F engine. The weight of one cannon with shells was 237 kg.
NS-37 production was carried out at the Izhevsk Factory No. 74, which initially manufactured both NS-37 and Sh-37 models. The first batch of 40 motorized NS-37 cannons was assembled between October 18 and December 7, 1942.
In 1943, 1880 motorized and 2849 wing-mounted NS-37 cannons were produced. In 1944, 890 motorized and 197 wing-mounted models were made. In 1945, 977 cannons were produced. By the end of production, a total of 6833 NS-37 cannons were made (8090 according to the KBP book).
The effectiveness of large-caliber aircraft cannons, such as the 37mm and larger, during World War II is assessed differently by historians. When targeting ground targets, the effectiveness of each cannon type depended on the target’s nature. For example, when shooting at open infantry positions, the effect of a 7.62mm bullet was not significantly different from that of a 20mm or 37mm shell, as the fragmentary effect was weak, and a direct hit was required to cause casualties (this does not apply to multi-element shells).
However, for targets like trucks, railway stations, and small boats, 7.62mm to 12.7mm machine guns were ineffective, while larger-caliber aircraft cannons became much more effective, especially with 37mm to 45mm shells.
The mass destruction of tanks by aircraft guns, often depicted in films and memoirs, is mostly exaggerated. Penetrating the vertical armor of medium or heavy tanks with a 20mm to 45mm aircraft cannon was impossible. Such shells could only penetrate the much thinner roof armor of tanks, which was around 15-20mm for medium tanks and 30-40mm for heavy tanks. Both caliber and sub-caliber armor-piercing shells were used, with no explosive content, sometimes only small amounts of incendiary material.
During the war, a test was conducted at the NIIBT polygon, where NS-37 shells were fired at stationary tanks. From a distance of 300-400 meters, three hits were achieved out of 35 shots from a LaGG-3, and three hits out of 55 shots from an IL-2. It’s worth noting that not every small-caliber shell that penetrated tank armor would disable the vehicle.
This is why the Germans and Americans attempted to mount 50mm to 75mm anti-tank guns on aircraft. While most of these guns were semi-automatic, it didn’t matter much as only one accurate shot was needed for effectiveness.
In total, Soviet medium and heavy tank losses during the war, by cause of destruction, were as follows: 88-91% from artillery; 8-4% from mines and fuzes; 4-5% from bombs and aircraft fire. However, in certain operations, losses from aircraft fire reached 10-15%.
