Editing Iowa-class battleship (section)

====Main battery====
{{multiple image
| direction= vertical
| width  = 220
| footer =
| image1 = Iowa 16 inch Gun-EN.svg
| alt1   = A multicolor cutaway of a 16in gun turret. Within the cutaway black lines point to various areas and objects of note, at the other end of the black lines English labels are given for identification purposes.
| caption1= Cutaway of a 16"/50 gun turret.
| image2 = Uss iowa bb-61 pr.jpg
| alt2   = An overhead view of a large ship with a teardrop shape firing guns toward the top of the image.
| caption2= {{USS|Iowa|BB-61|6}} fires a full broadside of nine 16-inch and six 5-inch guns during a gunnery exercise (1984)
| image3 = USS Iowa gun load.jpg
| alt3   = A ship deck with blue bullet and six drum shapes lined up behind the bullet
| caption3= 16"/50 gun projectile with six propellant bags (display) aboard USS ''Iowa'' (BB-61)
}}
The primary guns used on these battleships are the nine {{convert|16|in|0|adj=on}}/50-caliber Mark 7 naval guns, a compromise design developed to fit inside the barbettes. These guns fire high explosive- and armor-piercing shells and can fire a 16-inch shell approximately {{convert|23.4|nmi|km mi}}.{{sfn|Thompson|1999|pp=70–81}}<ref name="NavWeaps 16/50">{{Harvard citation no brackets|NavWeaps.com|loc= [http://www.navweaps.com/Weapons/WNUS_16-50_mk7.php 16"/50 Mark 7]}}</ref> The guns are housed in three 3-gun turrets: two forward of the battleship's [[superstructure]] and one aft, in a configuration known as "2-A-1". The guns are {{convert|66|ft}} long (50 times their 16-inch bore, or 50 calibers from [[breechface]] to [[Muzzle (firearms)|muzzle]]). About {{convert|43|ft}} protrudes from the gun house. Each gun weighs about {{convert|239000|lb}} without the breech, or {{convert|267900|lb}} with the breech.<ref name="NavWeaps 16/50" /> They fired {{convert|2700|lb|0|adj=on}} armor-piercing projectiles at a muzzle velocity of {{cvt|2500|ft/s|0|lk=on}}, or {{convert|1900|lb|0|adj=on}} high-capacity projectiles at {{cvt|2690|ft/s|0}}, up to {{convert|24|mi|nmi km}}.{{refn|The actual range of the ''Iowa''-class battleship's 16"/50 caliber guns varies from source to source. The most commonly cited distance for the 16"/50 caliber gun is approximately 20 miles; however, this number does not necessarily take into consideration the age of the gun barrel, the gun barrel's elevation, the projectile variant (armor piercing or high explosive), or the powder charges required to launch the artillery shell, all of which affect the range that a shell fired from a 16"/50 caliber gun can attain. The longest confirmed shot fired against an enemy naval unit using a 16"/50 caliber gun appears to have occurred during the raid against Imperial Japanese Navy units at [[Chuuk Lagoon|Truk Atoll]], when ''Iowa'' straddled a destroyer at 35,700 yards,<ref name="straddle"/> while the longest shot ever fired by a 16"/50 caliber gun in a non-combat situation is alleged to have occurred during an unauthorized naval gunnery experiment conducted 20 January 1989 off the coast of [[Vieques, Puerto Rico]] by ''Iowa''{{'}}s [[Master Chief Petty Officer|Master Chief]] [[Fire Controlman]], Stephen Skelley, and Gunnery Officer, [[Lieutenant commander (United States)|Lieutenant Commander]] Kenneth Michael Costigan, who claimed that one of the 16-inch shells traveled {{convert|23.4|nmi|km|-1}}.{{not in citation given|date=October 2024}} In addition, the standard 20-mile range does not take into account experimental artillery shells that were under consideration for use with the 16"/50 caliber gun in the 1980s, some of which are alleged to have been capable of traveling distances in excess of the often cited 20-mile gun range. One example is the Improved HC shell, which is said to have been test fired from ''Iowa'' at Dahlgren sometime after her 1980s recommissioning and is alleged to have achieved a range of over 51,000 yards.<ref name="NavWeaps 16/50" /> |group=N|name=Distance}} At maximum range, the projectile spends almost {{fraction|1|1|2}}&nbsp;minutes in flight. The maximum firing rate for each gun is two rounds per minute.<ref name="BAW">Poyer, pp. 50–53.</ref>

Each gun rests within an armored turret, but only the top of the turret protrudes above the main deck. The turret extends either four decks (Turrets 1 and 3) or five decks (Turret 2) down. The lower spaces contain rooms for handling the projectiles and storing the powder bags used to fire them. Each turret required a crew of between 85 and 110 men to operate.<ref name="NavWeaps 16/50" /> The original cost for each turret was US$1.4&nbsp;million, but this figure does not take into account the cost of the guns themselves.<ref name="NavWeaps 16/50" /> The turrets are "three-gun", not "triple", because each barrel is individually sleeved and can be elevated and fired independently. The ship could fire any combination of its guns, including a [[Broadside (naval)|broadside]] of all nine. The fire control was performed by the Mark 38 Gun Fire Control System (GFCS); the firing solutions were computed with the Mark 8 rangekeeper, an analog computer that automatically receives information from the director and Mark 8/13 fire control radar, stable vertical, ship pitometer log and gyrocompass, and anemometer. The GFCS uses remote power control ([[Glossary of British ordnance terms#RPC|RPC]]) for automatic [[gun laying]].<ref name="Mk38">{{cite web |url=http://www.dustdevil.com/ppl/billgx/mk38.htm  |title=Mark 38 Gun Fire Control System |access-date=2007-08-01 |archive-url = https://web.archive.org/web/20041028050854/http://www.dustdevil.com/ppl/billgx/mk38.htm |archive-date = 2004-10-28}}</ref>

The large-caliber guns were designed to fire two different conventional 16-inch shells: the {{convert|2700|lb|0|adj=on}} Mk 8 "Super-heavy" [[APCBC|APC]] (Armor Piercing, Capped) shell for anti-ship and anti-structure work, and the {{convert|1900|lb|0|adj=on}} Mk 13 high-explosive round designed for use against unarmored targets and shore bombardment.{{sfn|Sumrall|1988|pp=73–76}} When firing the same conventional shell, the 16-inch/45&nbsp;caliber Mark 6 used by the fast battleships of the ''North Carolina'' and ''South Dakota'' classes had a slight advantage over the 16-inch/50&nbsp;caliber Mark 7 gun when hitting deck armor&nbsp;– a shell from a 45&nbsp;cal gun would be slower, meaning that it would have a steeper trajectory as it descended. At {{convert|35000|yd|mi km}}, a shell from a 45&nbsp;cal would strike a ship at an angle of 45.2&nbsp;degrees, as opposed to 36&nbsp;degrees with the 50&nbsp;cal.<ref name="NavWeaps 16/45">{{Harvard citation no brackets|NavWeaps.com|loc= [http://www.navweaps.com/Weapons/WNUS_16-45_mk6.php 16"/45 Mark 6]}}</ref> The Mark 7 had a greater maximum range over the Mark 6: {{convert|23.64|mi}} vs {{convert|22.829|mi}}.<ref group=N name=Distance/><ref name="NavWeaps 16/45" /><ref>{{cite web|url=http://www.combinedfleet.com/baddest.htm |title=Battleship Comparison |publisher=Combinedfleet.com |access-date=2012-08-07}}</ref>

In the 1950s, the W23, an adaptation of the [[W19 (nuclear artillery shell)|W19 nuclear artillery shell]], was developed specifically for the 16-inch guns. The shell weighed {{convert|1900|lb|0}}, had an estimated yield of {{convert|15|to|20|ktonTNT|GJ|lk=in}},{{sfn|Yenne|2005|pp=132–133}} and its introduction made the ''Iowa''-class battleships' 16-inch guns the world's largest [[nuclear artillery]]{{sfn|Polmar|2001|p=490}} and made these four battleships the only US Navy ships ever to have nuclear shells for naval guns.{{sfn|Polmar|2001|p=490}} Although developed for exclusive use by the battleship's guns it is not known if any of the ''Iowa''s actually carried these shells while in active service due to the United States Navy's policy of refusing to confirm or deny the presence of nuclear weaponry aboard its ships.{{sfn|Yenne|2005|pp=132–33}}{{refn|"Military members and civilian employees of the Department of the Navy shall not reveal, report to reveal, or cause to be revealed any information, rumor, or speculation with respect to the presence or absence of nuclear weapons or components aboard any specific ship, station or aircraft, either on their own initiative or in response, direct or indirect, to any inquiry. [...] The Operations Coordinating Board (part of President Eisenhower's National Security Council) established the US policy in 1958 of neither confirming nor denying (NCND) the presence or absence of nuclear weapons at any general or specific location, including aboard any US military station, ship, vehicle, or aircraft."<ref>{{cite web |last=Morgan | first=J.G. Jr. |date=3 February 2006 |title=Release of Information on Nuclear Weapons and on Nuclear Capabilities of U.S. Forces (OPNAVINST 5721.1F N5GP) |publisher=Department of the Navy&nbsp;– Office of the Chief of Naval Operations |location=Washington, DC |pages=1–2 |url=http://www.fas.org/irp/doddir/navy/opnavinst/5721_1f.pdf |access-date=2012-07-02 }}</ref>|group=N|name=Nuclear}} In 1991, the United States unilaterally withdrew all of its nuclear artillery shells from service, and the dismantling of the US nuclear artillery inventory is said to have been completed in 2004.{{sfn|DeVolpi|Minkov|Simonenko|Stanford|2005|p=VA-13}}