Interest
Smith & Wesson "Military and Police"
revolver.
A
gun is a device 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.
In ordinary speech the term gun may refer to any sort of
firearm including those that are usually hand-held (
handgun).
The word gun is also commonly used to describe objects which, while
they are not themselves weapons, produce an effect or possess a form
which is in some way evocative of a handgun or
longarm.
However, in contemporary military and naval parlance the term gun has a
very specific meaning and refers solely to any large-calibre,
direct-fire, high-velocity, flat-trajectory artillery piece employing an
explosive-filled hollowed metal
shell or
solid bolt
as its primary projectile. This later usage contrasts with
large-calibre, high-angle, low-velocity, indirect-fire weapons such as
howitzers,
mortars, and
grenade launchers which invariantly employ explosive-filled shells.