After the end of World War II, in 1946, a new 82 mm mortar was developed in the Soviet Union, with automatic loading using recoil energy. Already in 1955, a casemate automatic mortar under the designation KAM was adopted by the Soviet Army. V. Filippov was the leader and lead engineer of this project. Later, on the basis of the KAM mortar, its field version was designed, which received the designation F-82. The prototype successfully passed all the tests, and according to their results, the selection committee recommended that it be adopted and put into mass production. However, despite positive reviews and recommendations, the model was not adopted for service. After that, work in the direction of creating automatic mortars in the USSR was stopped for eight years.
Only in 1967 did engineers return to the development of this promising type of weapon. After three years of hard work, in 1970 the Soviet Army adopted an automatic 82 mm smoothbore mortar 2B9 with water cooling, which was the result of further improvement and development of the KAM casemate mortar. After its start of operation in the troops, it was decided to create a more improved model, in which water cooling was replaced by air. The new model, a towed version of the mortar, designated 2B9M "Cornflower", differed from its predecessor in the presence of a thicker barrel wall and the presence of cooling ribs located on its central part. After successful tests, the modernized mortar was put into mass production and adopted by the army in 1983. (According to some reports, this happened in 1982).
The design of the mortar was made according to the scheme that is used to create a breech-loading artillery gun. This scheme made it possible to fully automate the loading of the mortar. Opening the bolt, feeding to the loading line, sending mines into the chamber, locking the bolt and firing are carried out automatically. The loading mechanism was driven by the use of the energy of powder gases. The recoil energy arising from a shot is used to actuate, with the help of return springs, an automatic loading mechanism. Shooting can be carried out both in automatic mode and in single mode. Thanks to competent design solutions, the rate of fire of the Cornflower mortar was 170 rounds per minute, and the practical rate of fire was more than 100 rounds per minute. According to this indicator, at that time, it was much ahead of all known Western counterparts. The mortar barrel, equipped with a recoil mechanism, is attached to the upper machine, which is equipped with rotary devices that provide a horizontal aiming angle of 60 ° and a vertical aiming angle from 2 ° to 80 °. As the elevation angle increases, it is necessary to dig a depression in the ground at the breech. In the combat position, the wheels of the carriage are hung out, and the mortar rests on a jack and two beds equipped with openers. The transition from the traveling position to the combat position and vice versa takes no more than 90 seconds.
Shooting from the 2B9M was fired by 3V01 fragmentation shots consisting of a six-pointed mine (made of steel cast iron) O-832DU, the main Zh832DU and an additional 4D2, powder charges. The maximum firing range is 4250 meters, the minimum is 800 meters, the weight of the O-832DU 3 mine, 1 kg. When a mine explodes, at least 400 fragments are formed, the radius of continuous destruction (90% of standing objects) is at least 6 meters, within a radius of effective destruction, 18 meters, at least 40% of standing objects are affected. Also, a cumulative projectile was developed for firing at light armored targets for the mortar. Loading a cassette-type mortar, four coaxial mines in a cassette. Aiming the mortar at the target is carried out using the PAM-1 optical sight. Due to its small mass (632 kg), the 2B9M mortar can easily be moved by the forces of the calculation without using a vehicle. For long distances, the mortar moves, either in the body or by towing, using the 2F54 transport vehicle (specially created on the basis of the GAZ-66 car), together with which it is designated as the 2K21 system. The mortar is rolled into the 2F54 body using special ramps. However, in the 80s, the MT LB tracked tractor began to be used to transport the mortar, on which it was located on the site in the rear of the hull. The calculation of the mortar or the 2K21 system consists of four people: the commander, the gunner and the driver of the transport vehicle (he is also the ammunition carrier).
