Gun barrel - online puzzles

A gun barrel is a crucial part of gun -type ranged 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 introduced (via propellant combustion or via mechanical compression) behind a projectile in order to propel it out of the front end (muzzle) at a high velocity. The hollow interior of the barrel is called the bore. The measurement of the diameter of the bore is called the caliber. Caliber is usually measured in inches or millimetres.

The first firearms were made at a time when metallurgy was not advanced enough to cast tubes capable of withstanding the explosive forces of early cannons, so the pipe (often built from staves of metal ) needed to be braced periodically along its length for reinforcement, producing an appearance somewhat reminiscent of storage barrels being stacked together, hence the English name.