Designed and built on the chassis of the KV-1S. The development of a prototype started in January 1944. The 203-mm B-4 howitzer was mounted on the restored hull of a KV-1S. From March 1944 through to the beginning of April, the vehicle underwent trials. Despite successful trials, the S-51 never entered mass production.
Time for the successive autoreloading of each shell into the magazine.
Characteristics are specified for Siege 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%.