วันศุกร์ที่ 15 กุมภาพันธ์ พ.ศ. 2556
A gun is a weapon designed to discharge a projectile. The projectile may be solid, liquid, gas or energy and may be free, as with bullets and artillery shells, or captive as with Taser probes and whaling harpoons. The means of projection varies according to design but is usually effected by the action of gas pressure, either produced through the rapid combustion of a propellant or compressed and stored by mechanical means, operating on the projectile inside an open-ended tube in the fashion of a piston. The confined gas accelerates the movable projectile down the length of the tube imparting sufficient velocity to sustain the projectile's travel once the action of the gas ceases at the end of the tube or muzzle. Alternatively, acceleration via electromagnetic field generation may be employed in which case the tube may be dispensed with and a guide rail substituted.
The first firearms were invented in China in the 12th century, and the technology gradually spread through the rest of Asia and into Europe. Modern guns are typically described by their bore diameter (75mm) or calibre (7.62mm), the type of action employed (muzzle, breech, lever, bolt, revolver, semi-automatic, or automatic) together with the usual means of deportment (hand-held or mechanical mounting). They may be further distinguished by reference to the type of barrel used (rifled) and the barrel length (19 inch), the design's primary intended target (anti-aircraft), or the commonly accepted name for a particular variation (Gatling gun).
Gatling gun
