A lightweight version of the T20 medium tank with the M7 elongated chassis. The vehicle was developed in the first half of 1943. Unlike the T20 tank, the T21 featured reduced armor and lighter armament. The vehicle never entered mass production nor saw service.
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%.