Serious development began in June 1940 of an 8-inch (203 mm) gun that would have a range of 33,500 yards (30,600 m), a road speed of 25 mph (40 km/h), be transported in 2 loads weighing no more than 44,000 lb (20,000 kg) and be suitable for rail movement. Use of the carriage of the 240 mm howitzer M1 eased development, but the gun was very troublesome and wasn't standardized until January 1944. The main problems were excessive bore wear and poor accuracy, but it was felt that nothing better could be produced in a timely manner. Thus it entered production at a low rate and in small numbers.
Like the 240 mm howitzer, it was mounted on a stretched Heavy Tank T26E3 chassis that had an extra bogie wheel per side as the 8in Gun Motor Carriage T93, but the war ended before they could be used and were later scrapped.
An 8-inch US Army field gun in action during the bombardment of Brest.
It also shared transport wagons with the 240 mm howitzer. One six-wheeled wagon carried the M2 carriage and the other carried the barrel as shown below: This separate configuration required the use of the M2 truck-mounted crane for set up.