Development of a 3 inch self-propelled gun on the M3A3 Stuart chassis started in September 1942. Trials on the Aberdeen Proving Ground in November demonstrated that the gun was too heavy for the light tank chassis. Never entered mass production.
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%.