Firearm

A firearm is any type of gun that shoots projectiles using high explosive pressure generated from combustion (deflagration) of chemical propellant, most often black powder in antique firearms and smokeless powder in modern firearms. Small arms is a subset of light firearms that is designed to be readily carried and operated by an individual. The term "firearm" is however variably defined in both technically and legally in different countries (see legal definitions), and can be used colloquially (sometimes incorrectly) to refer to any type of guns.

The first firearms originated in 10th-century Song dynasty China (see gunpowder weapons in the Song dynasty), when bamboo tubes containing gunpowder and pellet projectiles were mounted on spears to make the portable fire lance, which was operable by a single person and was later used effectively as a shock weapon in the siege of De'an in 1132. In the 13th century, fire lance barrels were replaced with metal tubes and transformed into the metal-barreled hand cannon, and the technology gradually spread throughout Eurasia during the 14th century. Older firearms typically used black powder as a propellant, but modern firearms use smokeless powder or other explosive propellants. Most modern firearms (with the notable exception of smoothbore shotguns) have rifled barrels to impart a stabilizing spin to the bullet for improved external ballistics.

Modern firearms can be described by their caliber (i.e. bore diameter). For handguns and rifles this is given in millimeters or inches (e.g. 7.62mm or .308 in.); in the case of shotguns, gauge or bore (e.g. 12 ga. or .410 bore.). They are also described by the type of action employed (single-shot vs. repeating, e.g. muzzleloader, breechloader, lever, bolt, pump, revolver, semi-automatic, fully automatic, etc.), together with the usual means of deportment (i.e. handheld or mounted). Further classification may make reference to the type of barrel bore used (i.e. rifled vs smoothbore) and to the barrel length (e.g. 24 inches), to the firing mechanism (e.g. matchlock, flintlock, wheellock, caplock or primer-ignited such as needlefire, pinfire, teat-fire, rimfire and centerfire, as well as the atypical electronic firing), to the design's primary intended use (e.g. hunting rifle, service rifle), or to the commonly accepted name for a particular variation (e.g. Gatling gun).

Shooters aim firearms at their targets with hand-eye coordination, using either iron sights or optical sights such as scope, red dot or holographic sights. The effective range of handguns and shotguns generally does not exceed 100 metres (110 yd; 330 ft), while most rifles are accurate to 500 metres (550 yd; 1,600 ft) using iron sights, or to longer ranges whilst using optical sights. Purpose-built sniper rifles and anti-materiel rifles are accurate to ranges of more than 2,000 metres (2,200 yd). (Firearm rounds may be dangerous or lethal well beyond their accurate range; the minimum distance for safety is much greater than the specified range for accuracy.)