While the 18"/47 cal Mark A was used to test the new "Super Heavy" 18-inch AP shell, if the caliber had been selected, a new lightweight 18"/48 cal Mark 2 gun would have been built. The new lightweight 18-inch gun would have fired the 3,850 lb "Super Heavy" shell at muzzle velocity, with a design similar to the contemporary 16"/50 cal Mark 7 gun rather than the 1920s technology used in the 18"/47 cal Mark A construction.Sumrall pp.66
