I photographed this pair of 16-inch (406 mm) Mk. 13 Shells at the Mississippi Armed Forces Museum at Camp Shelby. The Army made use of surplus Naval Guns that were available when the South Dakota Class Battleships were canceled. These were mated to modified M1919 carriages for coastal defense, in some cases as Disappearing Guns. Here in the Puget Sound area, I have seen the smaller (yet massive) 10-inch Disappearing Guns in both the firing and “hidden” positions at Ft Casey. I can’t imagine how monstrous the 16-inch version must have been.