By the end of the 20s of the last century, the command of the Red Army came to the conclusion that it was necessary to create a new anti-aircraft gun. Airplanes became more and more planes, and Lender's anti-aircraft guns of caliber 76, 2 mm were less and less suited to the requirements of the present.
In this regard, attempts were made to create a modern 76-mm anti-aircraft gun.
However, the reality was that in the late 1920s and early 1930s, the Soviet design school was still very weak, and the production base of artillery factories was just beginning to be updated due to the supply of imported machine-tool equipment (mainly from Germany).
And on August 28, 1930, the BYUTAST society (the front office of the Rheinmetall company) signed a secret contract for the supply to the USSR of four prototypes and manufacturing technology for 7, 5 cm anti-aircraft guns (7, 5 cm Flak L / 59), which at that time have not even passed the test yet. The Germans were watched very closely by their former opponents in the First World War in terms of compliance with the terms of the Treaty of Versailles.
So it was not from a good life that the Germans shared the latest developments, they needed full-fledged tests.
The original samples, made in Germany, were tested at the Research Artillery Range in February-April 1932. In the same year, the gun was put into service under the name “76-mm anti-aircraft gun mod. 1931 (3-K) . Especially for her, a new shell with a bottle-shaped sleeve was developed, which was used only in anti-aircraft guns.
Automation, or rather, the semi-automatic of the gun, ensured the extraction of spent cartridges and closing the shutter during firing. The shells were loaded and fired manually.
The presence of semi-automatic mechanisms ensured a high combat rate of fire of the gun - up to 20 rounds per minute. The lifting mechanism made it possible to fire in the range of vertical guidance angles from -3 ° to + 82 °. By the standards of the early 30s, the anti-aircraft gun of the 1931 model was quite modern and had good ballistic characteristics.
A carriage with four folding beds provided a circular fire, and with a projectile weight of 6, 5 kg, the maximum height of destruction of air targets was 9 km. A significant disadvantage of the gun was that the transfer from the traveling position to the combat position took a relatively long time (about 5 minutes) and was a rather laborious operation. In addition, the two-wheeled vehicle was unstable when transported over rough terrain.
Several dozen guns (from 20 to 40) were installed on YAG-10 trucks. "Cargo" ZSU received the index 29-K. To install the anti-aircraft gun, the bottom of the car body was reinforced. The car was supplemented with four folding jack-type stops. The body in the stowed position was supplemented with protective armored sides, which in the combat position were reclined horizontally, increasing the service area of the gun. In front of the cargo platform, there were two charging boxes of 24 rounds each. On the drop sides there were places for four crew numbers.
On the basis of the 3-K gun, the 76-mm anti-aircraft gun of the 1938 model was developed. In order to reduce deployment time, the same gun was installed on a new, four-wheeled platform.
Thanks to the use of the new ZU-8 platform, the time for transferring the system from the traveling position to the combat position was reduced compared to 5 minutes to 1, 0-1, 5 minutes, and the platform's independent suspension of the wheels made it possible to transport the gun at a speed of up to 50 km / h instead of 35 km / h.
Before the war, the troops managed to receive 750 76-mm anti-aircraft guns mod. 1938 It was the most numerous medium-caliber anti-aircraft gun in the USSR at the beginning of the war.
Thanks to a bottle-shaped sleeve with an increased charge of gunpowder and a long barrel, the 76-mm anti-aircraft guns of 1931 and 1938 had excellent armor penetration. The BR-361 armor-piercing projectile, fired from the 3-K gun at a distance of 1000 meters at a 90 ° meeting angle, penetrated 85 mm armor. In the initial period of the war, this was more than enough to destroy any German tank.
In accordance with the pre-war plans, the anti-aircraft division of each rifle division of the Red Army, along with two four-gun batteries of 37-mm anti-aircraft guns, was to have a four-gun battery of 76-mm anti-aircraft guns. In addition, an anti-aircraft artillery battalion consisting of three six-gun batteries of 76-mm anti-aircraft guns was included in each corps. In total, taking into account the anti-aircraft artillery regiments of the country's air defense and divisions of the RGK and the Air Force, it was planned to have 4204 anti-aircraft guns with a caliber of 76 mm.
However, they did not manage to implement this program even partially. Literally a year after the adoption of the 76-mm gun mod. 1938, an even more powerful 85 mm anti-aircraft gun mod. 1939. It was she who took the place of the "three-inch" and, with minor changes, was produced by the industry throughout the Great Patriotic War.
Despite the strong external similarity of both guns, it is almost impossible to confuse them if you know two characteristic details: the 85-mm anti-aircraft gun of the 1939 model is equipped with a muzzle brake and has a conical section in the middle of the barrel. In contrast, the 3-inch barrel is perfectly straight.
Nevertheless, the Russified German woman fought on both sides of the front. In the first months of the war, a number of these guns fell into the hands of the Germans. And since the Germans did not disdain anything captured, the gun was adopted by the Wehrmacht under the old name 7, 5 cm Flak L / 59 (r).
On our side, 3-K won both the Finnish and the Great Patriotic War.
Tactical and technical characteristics:
caliber: 76, 2 mm;
barrel length: 4, 19 m;
weight while traveling: 4210 kg;
weight in battle: 3050 kg;
vertical guidance sector: from −3 ° to + 82 °;
horizontal guidance angle: 360 °;
effective fire height: 9300 m;
projectile weight: 6, 61 kg;
muzzle velocity: 815 m / s.
