A Firearm is a weapon from which projectiles are discharged by the ignition of an explosive propellant.
The word “firearm” is usually synonymous and interchangeable with the term “gun”. It usually does not include devices that launch guided missiles.
In US gun law, a "firearm" is a weapon which expels projectiles using an explosive propellant, but does not fit any definition of a specific class of weapon given in the National Firearms Act. For example, the Fostech Origin 12 SBV is not designed to be shouldered (having an arm brace "stock") and so is legally not a shotgun, is a smoothbore and so is not a handgun, fires a common sporting shotgun shell and so is not a Destructive Device, and does not fit the "readily concealable" criteria for an Any Other Weapon as it is over 26 inches long.
The large arms of ancient times likely started with catapults and trebuchets which launched projectiles, some of which were set aflame for more effect.
According to Professor James Riddick Partington’s book, A History of Greek Fire and Gunpowder, published 1960 as written and documented, the word for gunpowder in Chinese is huo yao and is found in the Chinese works, Wu Chin Tsung Yao which is a collection of books on military techniques. These books date to 1044. According to Professor James Riddick Partington’s book, A History of Greek Fire and Gunpowder, published 1960 the huo p’ao (translated to fire-thrower) was a military weapon. This was a military weapon made from an 3 inch (7.62 cm) diameter bamboo trunk, approximately 6 foot (183 cm) in length rapped in hemp rope. There is no evidence this weapon discharged projectile/s; only ejecta. This weapon could be considered the first “flame thrower”.
Also, according to Professor J.R. Partington, the first uses of gunpowder as a propulsive force within a gun (large arm) are from cannons. These peoples were: the Arab Moors in 1331; the Italians in 1341; the English in 1344; the French in 1345; the Germans in 1349; the Spaniards in 1359; and the balance of Europe by 1370. The Jesuit priests from Europe taught the Chinese how to cast bronze in 1618.
The first written document that contained a specific reference to a cannon was in Florence, Italy, in 1326.
The first small arms began to appeal sometime after 1413 when black powder was produced by moistening it and pounding it into cakes. These cakes were then broken up by hand. The result was a very grainy quality powder and no longer a finely ground powder. This helped greatly with the uniform ignition of black powder.
Firearms are usually categorized as either large arms or small arms.
- Large Arms: Those weapons that are used on a wheeled, carriaged or mounted system and are not categorized as a small arm, as well as any cartridge, shell or ball of 20mm (0.787 in) caliber or greater. Large arms include but are not limited to: cannons; naval guns; howitzers; anti-aircraft machine guns and some heavy machine guns; .50 caliber heavy machine guns are not large arms.
- Small Arms: Those weapons that can be carried by person or animal and may be held by a person or mounted on a bipod or tripod that is readily movable by a person; also, any caliber of 4 bore or less, cartridge of .50 BMG or less or ball of .54 caliber or less (with the exception of RPGs and handheld grenade launchers), are considered small arm calibers. Small arms include but are not limited to: pistols; muskets; shotguns; rifles; grenade launchers; light machine guns, general purpose machine guns and rocket-propelled grenades (RPGs).