Gun laying
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Gun laying is the process of aiming an artillery piece. The term is also applied to describe the process of aiming smaller calibre weapons by radar or computer control. The gun is typically rotated in a horizontal plane in order gain a line of sight to the target.
The artillery piece can sometimes also be elevated, or moved in the vertical plane, to range it to the target. This vertical alignment is necessary to compensate for the vertical profile trajectory of the shot from the point it leaves the muzzle to the point where it encounters its target. There are two possible paths that a shot can take to a target at a defined range. The lower trajectory is known as direct fire, and the higher trajectory is known as plunging fire.
In some gun mountings it is also possible to depress the gun, that is to move it in the vertical plane to point it below the horizontal, to fire down at a target. Such a facility is only of relevance if the gun is higher than its target, though in some muzzle loading guns, the gun must be depressed to load it. These movements, and the mechanism to handle the recoil of the gun, are provided by the gun mounting.
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[edit] Muzzle Loading Artillery
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In the days of cannon, guns were provided with trunnions that were mounted onto a gun carriage. The gunner and gun-crew levered the front or rear of the carriage to traverse the gun, and drove in or pulled out wedges under the breech to achieve elevation. When fired the whole cannon on its carriage rolled backward against the resistance of a block and tackle rig. The recoil pushed the gun back far enough for the crew to access the muzzle to reload it, and when loaded the same block and tackle was used to return the carriage to its firing point. In the early 17th century certain castles and fortifications were fitted with gunloops or artillery ports to allow cannon to be fired from within. Often there was limited angle variation due to the confined gun port size, due to the masonry design to protect castle defenders.
On sailing warships in normal operation the guns were lashed down to the gun decks in the recoiled position, and the gun ports closed. To "run out the guns" was to open the gun ports, and haul the cannon forward to the firing position, a very threatening gesture: more so if the guns were actually loaded since blackpowder charges in the guns degenerate swiftly, and unloading a cannon without firing it is a dangerous process.
[edit] Breech Loading Artillery
Field artillery pieces where the gun is mounted on a wheeled gun carriage usually have a gun trail, by which it is towed, and this is manhandled to traverse the gun, although modern artillery provides for the ability to make fine adjustments to lateral aiming without traversing the entire carriage. Gun elevation is commonly set by a screw mechanism, and the gun mounting provides at least some range of depression, to allow direct fire from a height. There is usually a mechanism to absorb the majority of the recoil built into the gun carriage so the gun bucks when fired, but does not need to be winched back into place after firing.
Some of the first examples of breech loading artillery found limited use during the American Civil War, however it was not until the end of the 19th century that it began to supersede older muzzle loading cannons. The effectiveness of quick firing breech loading artillery that did not have to be re-laid after every firing was proven during the trench warfare of the First World War.
[edit] Naval Advances
The first turreted warship to see service, the USS Monitor, revolutionized warfare at sea through the ability to bring all of its guns to bear without turning the ship. Naval guns mounted in batteries in gun turrets brought gun laying to a new level of sophistication. Turret traverse, gun elevation and recoil are managed using hydraulic power. Ballistic calculations are performed by analog computers called rangekeepers. The guns are fired electrically and a fire control system is arranged to fire the guns in sequence, firing each gun as the roll of the ship brings the gun to bear on its target.
[edit] Modern Artillery and Aiming Systems
Current fighting vehicles have automated gun laying systems that in addition to the traditional ballistic calculations add additional aiming data to compensate for additional factors such as air temperature, wind direction, compensation for the movement of the vehicle, and compensation for the wear and straightness of the gun barrel. Since the 1960s advanced military technology began to track targets using real time radar and other electronic intercept techniques; gradually these systems developed real time computer controlled targeting and firing systems to allow optimisation of gun laying, including ship, tank and ground based artillery.
