Barrel (firearms)
The barrel of a firearm is the tube, usually metal, through which a controlled explosion is released in order to propel a projectile out of the end at great speed.
The first guns were made in a time where metallurgy was not quite what it is today, so the pipe needed to be braced periodically along its length, producing an appearance somewhat reminiscent of a barrel.
Smallbore
Generally a smallbore gun refers to a rifle or a handgun that has an inside barrel diameter of less than .243(6mm) caliber.
See also
