Developed in 1945 on the basis of the IS-2 and IS-3 vehicles, under the supervision of Joseph Kotin. One of the distinctive features was the slope angle of armor plates. Passed trials successfully, but never entered service.
Time for the successive autoreloading of each shell into the magazine.
The improved system allows the time to be decreased for autoreloading the next shell upon firing the loaded shell when the corresponding indicator is displayed
Characteristics are specified for Siege mode.
The technical characteristics are displayed for the charged turbine mode.
Characteristics are specified for Rapid mode.
Reload time of the first and second guns on double-barreled vehicles.
Characteristics are specified for vehicles with crews trained to 100%.