Re: 1940 battleship machine gun
It might be come from the America WWII warplanes as B-17 or B-24 or other bomber. Sometime, they flew low with something wrong while flying, cause more weight, so all crews had to throw the guns, flak helmet, flak vest, gunner's bullet cases to the sea, that way, the plane can fly to land on the ground than crash into the sea with too heavy weight with not enough power engine problems.
Richard