Development started at the end of 1938. A prototype was produced in August 1939. The vehicle first saw combat in December 1939 at the Mannerheim Line. The tank was mass-produced from March 1940 through August 1942, with a total of 2,769 vehicles manufactured.
Time for the successive autoreloading of each shell into the magazine.
The technical characteristics shown are for the Siege mode
Characteristics are specified for a vehicle with crew members trained to 100%.