the M10A1 was judged to have superior automotive performance to the M10. Even though it produced only slightly less torque, the M10A1's engine was far lighter, and used a common fuel like the rest of the Army's vehicles (gasoline). By the time the test results were released in February 1944, the Army was committed to using the M10 overseas. As a result, the M10A1 was kept in the United States for training. The M10 and M10A1 had a crew of five; commander, gunner, loader, driver, and assistant driver. The driver and assistant driver (who also operated the vehicle's radio) were seated in the front hull and provided with periscopes. The unique design of the hull hatches to clear the gun mantlet meant that the driver's view directly to the left side was obstructed. He was provided with a second periscope at the edge of the hull for this purpose. The commander, gunner, and loader were all located in the turret. The commander sat on a folding seat at the right rear. The gunner, on the left side of the gun, normally stood to operate it, but he was also provided with a folding seat. The loader normally stood in the area behind the gun. A third folding seat was provided in the turret for the assistant driver in case he needed to assist the loader for any reason. Unlike the M4 tanks it was based upon, the M10 lacked an auxiliary generator, which forced the crew to run the main engines in order to recharge the vehicle's batteries. The engine noise and smoke could attract enemy fire, especially in close quarters, where the M10 was vulnerable due to its thin armor and open-topped turret. The lack of an auxiliary generator was rectified with the introduction of the M36 tank destroyer. Production Soon after reaching production, it was realized that the barrel of the 3-inch gun M7 was too heavy, to the point where it prevented traverse of the turret on a slope of more than four degrees. As an attempt to improve the figure to fifteen degrees, the Army ordered that the track grousers and antiaircraft machine gun be stored on the rear of the turret. This did not solve the balance problem, and on 21 December 1942, triangular "quick fix" turret counterweights made of lead, mild steel, or cast iron were authorized. The mild steel parts weighed 2,400 pounds.