Modern firearms can be described by their caliber (i.e. bore diameter). For pistols and rifles this is given in millimeters or inches (e.g. 7.62mm or .308 in.), or in the case of shotguns by their gauge (e.g. 12 ga. and 20 ga.). They are also described by the type of action employed (e.g. muzzleloader, breechloader, lever, bolt, pump, revolver, semi-automatic, fully automatic, etc.), together with the usual means of deportment (i.e. hand-held or mechanical mounting). Further classification may make reference to the type of barrel used (i.e. rifled) and to the barrel length (e.g. 24 inches), to the firing mechanism (e.g. matchlock, wheellock, flintlock, or percussion lock), to the design's primary intended use (e.g. hunting rifle), or to the commonly accepted name for a particular variation (e.g. Gatling gun).