Pivot gun

A pivot gun was a type of cannon mounted on a fixed central emplacement which permitted it to be moved through a wide horizontal arc.

[1] They were a common weapon aboard ships and in land fortifications for several centuries but became obsolete after the invention of gun turrets.

Their calibers ranged from a few inches to the giant 11-inch Dahlgren guns used by the United States Navy in the mid-19th century.

Pivot guns had a major disadvantage in warfare: they were very difficult to protect in battle and were necessarily very exposed, as they lay close to the surface of a ship's deck and required an open field of view.

Smaller guns, particularly secondary batteries and the primary armament of cruisers and destroyers, retained pivot mountings until the 1920s, when turrets generally replaced them.