The ISU-122 Assault Gun Development
Though the ISU-152 had only started production in December 1943, the plants production numbers of the ISU-152 out-numbered the production of the vehicles main gun, the 152mm ML-20S.
During the same month development started of a modified version armed with other Russian howitzer main guns by the Chelyabinsk Kirov Plant.
By using different main guns, the plant could meet the demand in numbers for assault gun vehicles for the Russian Army.
The first modified version modified version was armed with the Russian A-19S 122mm main gun. The prototype was called the Object 242. Being almost identical to the ISU-152, the only medications were minor and mostly for the mounting of the gun and ammo stowage.
It was accepted in to Russian service in March 1944 as the ISU-122 and the first deliveries were completed in April of the same year.
The second modified version developed after the first and was fitted with the D-25S 122mm as its main gun. Development started in September 1944 and the prototype was called Object 249.
The D-25S used a different breach system so was able to be loaded faster than the A-19S and thus had a higher rate of fire of 4 rounds per minute. The vehicle can be recognised by the addition of a muzzle brake at the end of the main gun.
Both the ISU-122 and ISU-122S remained in production until 1945. 1735 ISU-122 and 675 ISU-122S were built and remained in service with the Russian Army after the war for several years.
The ISU-122 Assault Gun Spec’s
Armament: 122mm Main Gun
Armour: gun mantlet 120mm thick steel
Dimensions: Length 6.8m / Width 3.07m / Height 2.46m
Weight: 41.8 tonne
Engine: 520bhp 12-cylinder diesel
Top Road Speed: 37 km/h
Operational Range: 240 km