Besides "towing" 37mm antitank guns, it was also tested directly mounted on the quartertons. In early 1941, the US Army's Tank Destroyer Command was urgently looking to make their antitank guns more mobile, to better serve their tactical doctrine. One of the first prototypes, the T2 37mm Gun Motor Carriage (GMC), mounted a standard 37mm gun and gun shield on a Bantam BRC-40, aiming forward over the hood. Seven of these were built and tested, starting in May 1941, but were found awkward. So instead, eleven T2E1 GMC units aimed the 37mm gun rearwards for trials. Shooting rearwards had advantages, but this configuration also proved difficult to man and operate the gun. The units were all dismantled to regular jeeps. In 1942, the larger ton Dodge WC-52 was converted and standardized as the M6 Gun Motor Carriage, with a rear-aiming 37mm M3 gun, but these also worked poorly in the field, and most were built back to regular WC-52 trucks. Further designs were tried with stretched 6-wheel jeeps, but by 1943, the 37mm guns had become largely ineffective against German tanks.