View source for 12-inch/50-caliber Mark 7 gun

{{Infobox weapon
|name= 12"/50 caliber Mark 5 Naval Gun
|image=USS Arkansas Main Guns Firing.jpg
|caption={{USS|Arkansas|BB-33}} firing her 12"/50 guns in battle practice prior to World War I
|origin= United States
|type= [[Naval gun]]
<!-- Type selection -->
|is_ranged=YES
|is_bladed=
|is_explosive=
|is_artillery=YES
|is_vehicle=
<!-- Service history -->
|service=1912-1952
|used_by=
* [[United States Navy]]
* [[Argentine Navy]]
|wars=
*[[World War I]]
*[[World War II]]
<!-- Production history -->
|designer=[[Bureau of Ordnance]]
|design_date=1910
|manufacturer=
*[[Washington Navy Yard|U.S. Naval Gun Factory]]
*[[Bethlehem Steel]]
|production_date=
|number=
*Mod 0: 28 (Nos. 180–182, 186–210)
*Mod 2: 3 (Nos. 183–185)
*Mod 3: 6 (Nos. 211–216)
*Export: 17 (Nos. 795–817, 919–920)
|variants=Mods 0–19
<!-- General specifications -->
|weight=
*{{cvt|121489|lb|kg}} (without breech)
*{{cvt|123160|lb|kg}} (with breech)
|length={{cvt|50|ft|7.25|in|m|2}}
|part_length={{cvt|49|ft|6.25|in|m|2}} bore (49.5 [[Caliber#Caliber as measurement of length|calibers]])
|width=
|height=
|crew=
<!-- Ranged weapon specifications -->
|cartridge={{cvt|870|lb}}[[Armour-piercing shell|armor-piercing]]
|caliber={{cvt|12|in|0}}
|action=
|rate= 2–3 rounds per minute
|velocity=
*{{cvt|2900|ft/s}} (full charge)
*{{cvt|2100|ft/s}} (reduced charge)
|range= {{cvt|23900|yd}} at 15° elevation
|max_range=
|feed=
|sights=
<!-- Artillery specifications -->
|breech=
|recoil=
|carriage=
|elevation=-5° to +15°
|traverse=−150° to +150°
}}
The '''12"/50 caliber Mark 7 gun''' (spoken "twelve-inch-fifty-caliber") was a [[United States Navy]]'s [[naval gun]] that first entered service in 1912. Initially designed for use with the {{sclass|Wyoming|battleship|4}} of [[dreadnought]] battleships, the Mark 7 also armed the [[Argentine Navy]]'s {{sclass|Rivadavia|battleship}}s.{{sfn|Navweaps|2016}}{{sfn|Friedman|2011|pp=172–173}}
==Design and development==
The {{convert|12|in|adj=on|abbr=out|0}}/50 caliber Mark 7 naval gun was only a slight improvement over the preceding American naval gun, the [[12"/45 caliber Mark 5 gun]]. As such, it was a very similar weapon, having been lengthened by five [[caliber (artillery)|calibers]] to allow for improved muzzle velocity, range, and penetrating power.  Designed to the specifications of the [[Bureau of Ordnance]], the Mark 7 was constructed at the [[Washington Navy Yard|U.S. Naval Gun Factory]] in Washington, D.C.{{sfn|Navweaps|2016}}{{sfn|Friedman|2011|pp=172–173}}{{sfn|DANFS|2015}}
The Mark 7 weighed {{cvt|124140|lb}} with the breech and was capable of firing two to three times a minute.  At maximum elevation of 15° it could fire an {{cvt|870|lb}} shell approximately {{cvt|20000|yd}}. With an initial muzzle velocity of {{cvt|2900|ft/s}}, the gun had a barrel life of 200 rounds, and was capable of firing either [[Armor Piercing|armor piercing]] or Common projectiles.{{sfn|Navweaps|2016}}{{sfn|Friedman|2011|pp=172–173}}
As designed, the Mark 7 was capable of penetrating {{cvt|17.4|in}} of [[Harvey armor|Harvey plated]] side armor at {{cvt|6000|yd}}, {{cvt|14.7|in}} at {{cvt|9000|yd}}, and {{cvt|12.3|in}} at {{cvt|12000|yd}}.{{sfn|Navweaps|2016}} By comparison the 12"/45 caliber Mark 5 it replaced could penetrate {{cvt|16.6|in}}, {{cvt|12.2|in}}, and {{cvt|9.9|in}} at those distances, respectively.{{sfn|Navweaps2|2016}}
[[Bethlehem Steel]] built the first gun, No. 180. Mod 0, Nos. 181, 182, and 186–200, was a [[built-up gun]] consisting of a tube, jacket, and eight [[hoop gun|hoops]], a screw-box liner with locking hoops and rings and hand operated and Smith-[[Asbury mechanism]]. The gun was constructed with [[nickel-steel]] and hooped to the muzzle.{{sfn|Friedman|2011|pp=172–173}}
Mod 1 was gun No. 180, rebuilt into gun No. 180L, with its chase hoops rebuilt along with a new conical nickel-steel liner, a smaller chamber, and the rifling increased.{{sfn|Friedman|2011|pp=172–173}}
Mod 2, gun Nos. 183–185, was a Mod 0 gun relined with a conical liner, a new chase locking hoop, and with a locking ring added. This brought the weight up to {{convert|125498|lb|abbr=on|0}}, with the breech. It also had a {{convert|25|cuin|abbr=on|0}}-smaller chamber.{{sfn|Friedman|2011|pp=172–173}}
The Mod 3 guns, Nos. 211–216, were the last new guns built, all other Mods were Mod 0, 2, or 3 guns that were modified. These guns were built with a new simplified design, no liner, five hoops, a locking ring, along with a screw-box liner and a different gas check seat.{{sfn|Friedman|2011|pp=172–173}}
Mod 4, the twelve guns from {{USS|Wyoming|BB-32|2}}, relined in 1921–1923, had a conical one-step liner and uniform rifling with a new chase locking hoop and locking ring. With the Mod 5 an attempt was made to reline a Mod 1 with a uniform twist rifling, but it was dropped. Mod 6 relined Mod 2 with a uniform twist rifling along with a modified new chase hoop and locking ring. Mod 7 took the Mod 3 and used a one-step conical liner, uniform twist rifling, and added a tube and liner locking ring. Mod 8 was the Mod 0 or Mod 4 also using a one-step conical liner, uniform twist rifling that was secured by a tube and liner locking ring with a liner locking collar at the breech end. The Mod 8s that used Mod 0 guns also added a new chase hoop and locking ring. Mod 9 was a Mod 2 or Mod 6 that had a new liner with longitudinal clearances at the liner shoulders installed, uniform twist rifling along with a tube and liner locking ring and collar added at the breech end. Mod 10, like the Mod 9, was also a Mod 2 or Mod 6 that had a new liner with longitudinal clearance at the liner shoulders installed, uniform twist rifling along with a tube and liner locking ring and collar added at the breech end. The Mod 10 used Breech Mechanism Mark 9 instead of the Mark 8 on the previous Mods. Mod 11 was a Mod 7 that had the chamber lengthened, adding {{cvt|235|cuin|0}}, and a 3½° breech band seating slope and used Breech Mechanism Mark 12. Mod 12 used a Mod 10 and lengthened the chamber and added a 3½° breech band seating slope with Mod 13 being similar but of a Mod 8, Mod 14 used a Mod 9, Mod 15 used a Mod 7, Mod 16 used a Mod 10, Mod 17 used a Mod 8, and Mod 18 a Mod 9. Mod 19, the last modification, used a Mod 2 with its breech modified for the Smith-Asbury Breech Mechanism and the forward end of the chamber modified similar to the Mod 18, lengthened the chamber and added a 3½° breech band seating slope. The breech end was further modified by being machined out so that it could accommodate a gas check seat liner locking ring. The Mod 19 could also be used right or left handed by cutting a new slide keyway that was 180° from the original keyway.{{sfn|Friedman|2011|pp=172–173}}
==Naval Service==
{|class="wikitable"
!Ship
!Gun Installed
!Gun Mount
|-
|{{USS|Wyoming|BB-32}}
|Mark 7: 12"/50 caliber
|Mark 9: 6 × twin turrets
|-
|{{USS|Arkansas|BB-33}}
|Mark 7: 12"/50 caliber
|Mark 9: 6 × twin turrets
|-
|{{ship|ARA|Rivadavia||}}
|Mark 7: 12"/50 caliber
|Mark 9: 6 × twin turrets
|-
|{{ship|ARA|Moreno||}}
|Mark 7: 12"/50 caliber
|Mark 9: 6 × twin turrets
|}
==Notes==
{{Reflist|2}}
==References==
{{refbegin}}
* {{cite book
| first=Norman
| last=Friedman
| url=https://books.google.com/books?id=yh3OAwAAQBAJ
| title=Naval Weapons of World War One
| publisher=Seaforth Publishing
| authorlink =Norman Friedman
| year=2011
| pages=172–173
| isbn=978-1-84832-100-7
}}
* {{cite web
|url=http://www.navweaps.com/Weapons/WNUS_12-50_mk7.php
|title=United States of America 12"/50 (30.5 cm) Mark 7
|publisher=Navweaps
|date=19 July 2016
|accessdate=18 October 2016
|ref= {{sfnRef|Navweaps|2016}}
}}
* {{cite web
|url=http://www.navweaps.com/Weapons/WNUS_12-45_mk5.php
|title=United States of America 12"/45 (30.5 cm) Mark 5 and Mark 6
|publisher=Navweaps
|date=11 April 2016
|accessdate=18 October 2016
|ref= {{sfnRef|Navweaps2|2016}}
}}
* {{cite DANFS
| title = Washington Navy Yard: History of the Naval Gun Factory, 1883-1939
| url =http://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/w/washington-navy-yard-history-naval-gun-factory.html
| publisher = Naval History and Heritage Command
| date= 30 April 2015
| accessdate = 2 June 2016
| ref={{sfnRef|DANFS|2015}}
}}
{{refend}}
==External links==
* [http://www.gwpda.org/naval/usn14gun.htm Bluejackets Manual, 1917, 4th revision: US Navy 14-inch Mark 1 gun]
{{WWIUSNavalWeapons}}
{{WWIIUSNavalWeapons}}
{{Use dmy dates|date=June 2017}}
{{DEFAULTSORT:12 50 Caliber Mark 7 Gun}}
[[Category:Naval guns of the United States]]
[[Category:305 mm artillery]]