In 1947, at the Omsk plant No. 147, the production of the SU-100 self-propelled artillery unit (ACS) was stopped, where its production was transferred from the Uralmash plant at the beginning of 1946. In accordance with the decree of the Council of Ministers of the USSR of June 22, 1948, the design bureau of the Omsk plant No. 174 (headed by I. S. Bushnev) was instructed to develop on the basis of the T-54 tank a preliminary design of a self-propelled artillery unit equipped with a 122-mm D-25 cannon … Completion date is July 1948.
The project of the installation and its model, made in full size, were considered by the Ministry of Transport Engineering only in December 1948. The delay was due to the untimely receipt of blueprints for the 122mm D-49 cannon from Plant No. 9, the small size of the design bureau, and the complexity of the task at hand. Later, the SPG project was finalized and in July 1949, along with the layout, they presented a special. a prototype commission, which included representatives of the command of BT and MB and NTK GBTU.
The customer approved the conclusion of the mock-up commission only in August 1949, after which the plant began preparing drawings of a self-propelled gun for the production of a prototype, but the work was suspended, since the design of the basic T-54 tank was not completed.
In October 1949, in accordance with the resolution of the Council of Ministers, work on the SU-122 was transferred from factory # 174 to factory # 183 in Nizhny Tagil. This decision was associated with the study of the possibility of equipping the T-54 tank with a 122 mm D-25 cannon. At the same time, by the decree of the Council of Ministers of the USSR No. 4742-1832s of 15.10.1949, the final tactical and technical requirements for the SU-122 were approved.
The design bureau of plant # 183 decided to change the SPG layout. They again started sketching, which again led to a delay in the deadline for the presentation of the project. But in May 1950, work on the SU-122 was returned to the design bureau of plant # 174, where it was continued according to the previous layout.
ACS SU-122, developed under the guidance of the chief designer of the project A. E. Sulina and received the designation "Object 600" at the design bureau of plant # 174, was a modern combat vehicle with a powerful cannon, anti-cannon armor protection, good visibility from the seats of the crew members, and also had sufficient mobility. The presence of a loading mechanism, rangefinder, blowing the barrel bore with compressed air, as well as free communication between the crew members were favorable conditions for conducting effective artillery fire and destroying both armored vehicles and powerful enemy fortifications.
The installation of a large-caliber anti-aircraft machine gun KPV, coaxial with a cannon, increased the protection of the ACS against melee weapons.
The first prototype SU-122, manufactured in December 1950 by plant No. 174, passed factory tests by the end of the year.
In June-July of the 51st year, the first stage of the state. tests, and in early August SU-122 entered the NIIBT test site for the second stage.
The use of a rangefinder made it possible, when firing from a spot, to hit a target of the "Tank" type at a distance of up to 3 thousand meters.
The tests revealed shortcomings in the operation of the KPV machine gun and increased efforts on the flywheels of its guidance, insufficient vertical accuracy of the KPV heavy machine gun, as well as unsatisfactory operation of the metering mechanism of the barrel bore blowing. Despite this, the self-propelled installation of the state. passed the tests. Immediately after that, plant # 174 began to make changes to the working drawings for the production of the pilot batch. Until January 1, 1952, the drawings were completed and transferred to production.
At the end of 1951, additional sea trials were carried out during which the SPG traveled 1,000 kilometers.
In the first quarter of next year, the second sample of the SU-122 was assembled, which passed factory tests from June to July.
According to the results of factory and state. tests of prototypes during the 3rd quarter of 1952, the necessary changes were made to the design of the anti-aircraft machine gun. But the production of prototypes of the self-propelled unit at the factory # 174 was suspended, since there were no 122mm D-49 cannons.
On March 15, 1954, in accordance with the decree of the Council of Ministers of the USSR No. 438-194, a self-propelled unit based on the T-54 was put into service, but serial production was only started in 1955.
The SU-122 was a closed self-propelled gun mount with an armored jacket in the front. The car's crew consisted of five people.
The control compartment and the fighting compartment were combined, so all crew members could freely communicate with each other. Placing a driver's workplace in the fighting compartment made it possible to reduce the height of the line of fire to 1505 millimeters and, therefore, improve the stability of the vehicle during firing. The engine-transmission compartment was located in the stern.
The main weapon is the 122 mm D-49 rifled gun, the barrel length of which was 48.7 caliber (5497 mm). The gun had a wedge-shaped horizontal semi-automatic shutter with electromechanical chambering and ejection blowing of the barrel bore. The blowing of the barrel served to reduce the amount of gases entering the fighting compartment during firing; for 122-mm guns, the ejector was installed for the first time. The gun was a modernized version of the D-25T cannon of the IS-3 tank. The gun was installed in a frame, which was fixed on the frontal sheet of the armored jacket.
When firing direct fire at a distance of up to 6 thousand meters, the TSh-2-24 telescopic sight was used, which has a variable magnification (3.5x, 7x), and when firing from a closed position at a distance of up to 13.4 thousand meters, the S71- sight was used. 24-1 and gun panorama. Angles of horizontal guidance in the sector 16 °, vertical - from -4 to + 16 °.
Thanks to the use of an electromechanical rammer, the rate of fire was 4-5 rounds per minute.
For firing from the cannon, high-explosive and armor-piercing shells were used, as well as high-explosive fragmentation grenades from D-30 and M-30 howitzers. After the American M60 tank and the English Chieftain appeared at the beginning of the 60s for the D-49 cannon, they developed armor-piercing cumulative and armor-piercing subcaliber projectiles.
A coaxial 14.5 mm KPVT machine gun was installed to the right of the cannon. There was also a second KPVT machine gun with an anti-aircraft mount. The turret of the anti-aircraft machine gun was mounted on the base of the loader's hatch.
The self-propelled gun's ammunition consisted of 35 rounds and 600 cartridges for KPVT machine guns.
Projectile armor protection of the welded body of the SPG was made of rolled armor plates.
The power plant, the transmission with the control system and the chassis, with some design changes, were borrowed from the T-54 tank.
For the first time in domestic tank building, an AK-150V air compressor borrowed from aviation (without design changes) was used in the compressed air engine starting system, but since it was not adapted to work in the conditions of movement of a self-propelled artillery unit, its revision was required. Compressed air was used not only to start the diesel engine and pneumatic reloading of the KPVT machine gun, but also to clean the ammunition and aggregates from dust. Since the center of gravity of the machine has shifted forward, in the undercarriage, the relative position of the road wheels was changed and the angle of twist of the torsion shafts was reduced, which made it possible to obtain a more even distribution of the load.
Serial production of the SU-122 ("Object 600") was carried out in Omsk at the plant No. 174 in 1955-1957 on the basis of the T-54A. During this period, 77 machines were manufactured, after which their production was curtailed, since the government decided to stop work on barrel artillery. In addition, at the same time, ATGMs (self-propelled anti-tank missile systems) on tracked and wheel bases were created and adopted.
