Firearms. Originally: †a bullet, charge, etc., that occupies the full diameter of a gun barrel; the size of a bullet, charge, etc., for a weapon of…

(See quot. 1671.)

Military. ordered arms: a position assumed by a soldier in which a firearm is held vertically on the right side with its butt touching the ground…

(a) a double-barrelled gun; (b) a hyphenated surname (cf. 2).

A cannon or gun of which the barrel is made with a smooth or unrifled bore.

jocularly. A firearm discharged at a pursuer.

Ordnance. Short for shunt (rifled) gun n., also a curve in the rifling of a shunt rifled gun (see compounds 2).

a method of rifling cannon so that the projectile undergoes a shunt or lateral change of position in the process of loading; so shunt (rifled) gun…

Firearms. A firearm in which the lock (lock, n.2 5) is to the side of the action. Frequently attributive, designating a firearm of this type.

With modifying word. A gun that fires in the specified way, or fires the specified ammunition.

Originally and chiefly U.S. A slide-action firearm (see sense B.); = pump-action, n. 2.

Esp. in the war in Vietnam: a weapon, or ammunition, the calibre of which is measured in millimetres; a millimetre (chiefly attributive).

A multicalibre firearm.