Development of the SPG started in the second half of 1941. The prototype underwent trials on February 12, 1942 and saw service in July 1942. The Pressed Steel Car Company produced 100 vehicles. Baldwin Locomotive Works modified the SPGs and re-equipped some M30 carriers. The vehicle saw service in the field artillery battalions and was used by the U.S.A. forces in Western Europe.
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
Time to repair a damaged main/reserve track
Characteristics are specified for vehicles with crews trained to 100%.