A gun barrel is a crucial part of gun-type weapons such as small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure gas(es) is used to propel a projectile out of the front end (muzzle) at a high velocity. The hollow interior of the barrel is called the bore, and the diameter of the bore is called its caliber, usually measured in inches or millimetres.
The Tsar Cannon of 1586 with its huge bore and a barrel exterior which is perceived like a stack of storage barrels
A female worker boring out the barrel of a Lee-Enfield rifle during WWI
The barrel of a 240 mm howitzer in use in 1944
A German Army G22 with fluted barrel
A gun is a device designed to propel a projectile using pressure or explosive force. The projectiles are typically solid, but can also be pressurized liquid, or gas. Solid projectiles may be free-flying or tethered. A large-caliber gun is also called a cannon.
SIG Pro semi-automatic pistol
Battleship USS Iowa fires a full broadside from its nine sixteen-inch naval guns
A 'flying-cloud thunderclap-eruptor,' a proto-gun firing thunderclap bombs, from the Huolongjing.
The first firearm (a "proto-gun"), the fire lance, from the Huolongjing.