A gun is a common name given to an object that propels another object or projectile. The projectile is generally fired through a hollow tube known as the gun's barrel. The projectile's caliber is usually designated in fractions of an inch or in millimeters. Differing from the musket, most modern guns are rifled, with a series of grooves spiraling along the barrel; exceptions include smoothbores on tanks, AFV and some artillery. fires a full broadside during a target exercise near Vieques Island, Puerto Rico, 1 July 1984.]]The term gun is often used synonymously with firearm, but this is common only for civilian usage. In military usage, the term refers only to artillery that fires projectiles at high velocity, such as naval guns (which are never referred to as cannon) or tank guns. A gunner is a member of the team charged with the task of operating and firing a gun. By military terms, mortar and all hand-held firearms are excluded from the definition of