|Manufacturer||Cleveland Tractor Co.||Crew||
|3" Gun M6||On rear of chassis||33 rounds||68°
(34° left and right;
|+15° to -8°
|Engine||Hercules DWX DFS; 6 cylinder, supercharged, inline diesel|
|Transmission||Clark model 275 VO-1, 5 speeds|
|Steering||Controlled differential, steering levers|
|Type||Road wheels||Track return rollers|
|Vertical volute spring||2 bogies/track;
2 dual wheels/bogie
|Drive sprockets||Idlers||Front drive||Dual trailing adjustable at rear of track|
|Center guide, reinforced rubber with replaceable rubber shoes|
|Ground contact length||95"
|Max level road speed||38mph
|Min turning diameter||34'
The 3" GMC M5 was based on the Cleveland Tractor Company's (Cletrac) seven-ton high speed tractor MG-2. The 3" gun M6 was ballistically identical to the 3" gun M7 later found on the heavy tank M6 and 3" GMC M10. The only armor on the vehicle was provided by the gun shield and two small shields in front of the driver's and assistant driver's/gunner's positions; these men sat in front of the rear-mounted gun during travel and therefore would have had no protection from the gun shield. The project was begun in December 1940, and the vehicle was standardized in January 1942 with intentions to procure 1,580 carriages. A protracted development period--during which the vehicle's estimated weight increased by almost 50%--as well as problems with reliability, structural integrity, small ammunition load, and track failures led to the cancellation of the project in August 1942 before production had actually started. At that point, work on the M10 was far enough along that the first production examples of this much more successful vehicle were accepted the next month.