A 5-inch diameter projectile fired by a naval gun. Usually refers to the ammunition for the U.S. and NATO Mk. 45 5"/54-caliber autoloading naval gun. 5" shells these days tend to be used for antiaircraft and more importantly anti-cruise missile duties. Spins from barrel rifling; range around 13 nautical miles unmodified. Can be modified to gain additional range using base bleed, base burn or base boost. Each of these has a negative impact on accuracy, however. Also, in the U.S. Navy at least, the largest (not last; thanks to Transitional Man for pointing out the 3" OTO Melara mounts) surviving naval cannon in active duty, with the retiring of the Iowa-class Battleships.