A round shot is a solid spherical projectile without explosive charge launched from a gun. Its diameter is slightly less than the bore of the barrel from which it is shot. This design which is "slightly less than the diameter" is to seal the powder to make it explode and make the solid sphere blows out. Sometimes this round shot fails due to atmospheric air that enters the powder. A round shot fired from a large-caliber gun is also called a cannonball.
