Pivot gun

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Gunners operating a pivot gun aboard a United States Navy vessel in the late 19th century Pivot gun usnavy.jpg
Gunners operating a pivot gun aboard a United States Navy vessel in the late 19th century

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

Cannon Class of artillery which fires at a low or flat trajectory

A cannon is a type of gun classified as artillery that launches a projectile using propellant. In the past, gunpowder was the primary propellant before the invention of smokeless powder during the 19th century. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees, depending on their intended use on the battlefield. The word cannon is derived from several languages, in which the original definition can usually be translated as tube, cane, or reed. In the modern era, the term cannon has fallen into decline, replaced by guns or artillery if not a more specific term such as mortar or howitzer, except for high calibre automatic weapons firing bigger rounds than machine guns, called autocannons.

Gun turret protective weapon mount or firing position

A gun turret is a location from which weapons can be fired that affords protection, visibility, and some cone of fire. A modern gun turret is generally a weapon mount that houses the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in some degree of azimuth and elevation.

History

By mounting a cannon on a pivot, a much wider arc of fire could be obtained than was possible with conventional carriage-mounted cannons. Unlike the latter, however, pivot guns were fixed in one place and could not easily be moved outside of their horizontal arc; they could thus only really be used in fixed positions such as in a fort or on a battleship.

There was no standard size of pivot gun, though they tended to be fairly substantial weapons. Like other cannons, they were muzzleloaders and could fire either shells or grapeshot (or other types of shot). 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.

Muzzleloader class of gun which is loaded from the muzzle

A muzzleloader is any firearm into which the projectile and usually the propellant charge is loaded from the muzzle of the gun. This is distinct from the more popular modern designs of breech-loading firearms. The term "muzzleloader" applies to both rifled and smoothbore type muzzleloaders, and may also refer to the marksman who specializes in the shooting of such firearms. The firing methods, paraphernalia and mechanism further divide both categories as do caliber.

Shell (projectile) projectile

A shell is a payload-carrying projectile that, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot. Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used. Originally, it was called a "bombshell", but "shell" has come to be unambiguous in a military context.

Grapeshot type of ammunition shooting mutliple small balls

In artillery, grapeshot is a type of shot that is not one solid element, but a mass of small metal balls or slugs packed tightly into a canvas bag. It was used both in land and naval warfare. When assembled, the balls resembled a cluster of grapes, hence the name. On firing, the balls spread out from the muzzle, giving an effect similar to a giant shotgun.

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. In the late 19th century they were replaced by "disappearing guns" and ultimately by turrets, which enabled a broad arc of fire while providing the gunners with all-round protection from incoming fire.

Disappearing gun

A disappearing gun, a gun mounted on a disappearing carriage, is an obsolete type of artillery which enabled a gun to hide from direct fire and observation. The overwhelming majority of carriage designs enabled the gun to rotate backwards and down behind a parapet, or into a pit protected by a wall after it was fired; a small number were simply barbette mounts on a retractable platform. Either way, retraction lowered the gun from view and direct fire by the enemy while it was being reloaded. It also made reloading easier, since it lowered the breech to a level just above the loading platform, and shells could be rolled right up to the open breech for loading and ramming. Other benefits over non-disappearing types were a higher rate of repetitive fire and less fatigue for the gun crew.

Pivot guns should not be confused with swivel guns, a much smaller type of ordnance.

Swivel gun cannon

The term swivel gun usually refers to a small cannon, mounted on a swiveling stand or fork which allows a very wide arc of movement. Another type of firearm referred to as a swivel gun was an early flintlock combination gun with two barrels that rotated along their axes to allow the shooter to switch between rifled and smoothbore barrels.


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Artillery battery artillery unit equivalent to an infantry company

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Wall gun

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Barbette

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Rifled muzzle loader artillery class

A rifled muzzle loader (RML) is a type of large artillery piece invented in the mid-19th century. In contrast to smooth bore cannon which preceded it, the rifling of the gun barrel allowed much greater accuracy and penetration as the spin induced to the shell gave it directional stability. Typical guns weighed 18 tonnes with 10-inch-diameter bores, and were installed in forts and ships.

Casemate

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Coastal artillery Military service branch equipped with artillery in defense of territory against attack from the sea

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Naval artillery artillery mounted on a warship

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Gun laying

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Columbiad

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