View source for 6-inch/40-caliber gun

{{Infobox weapon
|name=6"/40 caliber Mark 4
|image=USS Massachusetts 6 inch gun and crew LOC 4a14403v.jpg
|image_size=300
|caption={{USS|Massachusetts|BB-2}}, 6-inch/40 caliber gun and crew.
|origin= United States
|type=[[Naval gun]]
<!-- Type selection -->
|is_ranged=YES
|is_bladed=
|is_explosive=
|is_artillery=YES
|is_vehicle=
<!-- Service history -->
|service=1885
|used_by= [[United States Navy]]
|wars=
* [[Spanish–American War]]
* [[World War I]]
<!-- Production history -->
|designer=[[Bureau of Ordnance]]
|design_date=1883
|manufacturer=[[Washington Navy Yard|U.S. Naval Gun Factory]]
|production_date=1896 – 1905
|number=72 (Nos. 133–196, 260–263, and 423–426)
|variants=Mark 4 Mod 0 – Mod 13 (no Mod 6)
<!-- General specifications -->
|weight={{cvt|13370|lb}} (without breech)
|length=
* Mod 0: {{cvt|256.1|in}}
* Mod 1: {{cvt|254.61|in}}
|part_length={{cvt|240|in}} bore (40 [[Caliber#Caliber as measurement of length|calibers]])
|width=
|height=
|crew=
<!-- Ranged weapon specifications -->
|cartridge={{cvt|105|lb}} naval [[Armour-piercing shell|armor-piercing]]
|caliber={{cvt|6|in|0}}
|action=
|rate=
* As commissioned:  1.5 rounds per minute
* After 1906: 7.6 rounds per minute
|velocity={{cvt|2150|ft/s}}
|range=
* {{cvt|9000|yd}} at 15.3° elevation
* {{cvt|18000|yd}} at 30.2° elevation
|max_range=
|feed=
|sights=
<!-- Artillery specifications -->
|breech=
|recoil=
|carriage=
|elevation=
|traverse=−150° to +150°
}}
The '''6"/40 caliber gun Mark 4''' (spoken "six-inch-forty-caliber") were used for the secondary batteries of the [[United States Navy]]'s {{sclass|Indiana|battleship|0}} and {{sclass|Illinois|battleship|0}} [[battleships]]. They were also used as the main battery on the {{sclass|Cincinnati|cruiser|0}} [[protected cruiser]]s.{{sfn|Navweaps|2015}}{{sfn|Friedman|2011|p=180}}
==Design==
The {{convert|6|in|0|adj=on|abbr=out}}/40 caliber Mark 4 guns were developed before the [[Spanish–American War]] and still used [[black powder]] or [[brown powder]], in later years they were not considered strong enough to withstand the higher chamber pressures generated by the newer [[smokeless powder]] adopted around 1898. Many were obsolete before the start of [[World War I]], namely the Mods 0, 1, 2, 3, and 8, and were removed from service, however, since they were stronger than the earlier Mark 1, 2, and 3s, 45 of them were still in active service June 1917.{{sfn|Navweaps|2015}}
The first Mark 4, gun No. 133, was completed July 1896. Production numbers were Nos. 133–196, 260–263, and 423–426. It was the first 6-inch Navy gun designed from the beginning to use case, [[Shell (projectile)#Separate loading cased charge|semi-fixed]], ammunition. The gun was constructed of gun steel using a [[Built-up gun|tube]], jacket, and seven [[Hoop gun|hoops]]. It was originally threaded to be mounted in the Mark 5 gun mount. Mod 0 was very similar to the Mark 3 Mod 2 but with the breech ring lengthened {{cvt|0.1|in}}, the [[trunnion]] hoop removed and the barrel threaded.{{sfn|Navweaps|2015}}{{sfn|Friedman|2011|p=180}}
Mod 1, No. 155, was of similar construction, but was {{cvt|0.31|in}} longer, only 4 hoops, and an experimental breech mechanism. The chamber volume was also increased slightly from {{cvt|1320|cuin}} to {{cvt|1367|cuin}}. Mod 2, for Mark 6, 7, and 9 gun mounts, was similar but with {{cvt|1.8|in}} cut off the breech end of the gun. Only one gun, No. 136, was modified in this way. Mod 3 was similar in construction to the Mod 1 but with its mounting threads located differently and it also had a threaded bronze sleeve. Mod 4 only differed from Mod 1 construction in adding a shoulder for a mounting yoke and with a different location for the mounting threads. The chamber volume was reduced slightly to {{cvt|1355|cuin}}. Mod 5 only differed from Mod 4 in adding a muzzle bell. Mod 6 was skipped and Mod 7 was an experimental Mod 4 bored out to use bag ammunition, a 1,367 cu in chamber, {{cvt|1.83|in}} think faceplate added to the breech end, and a trunnion hoop added. With Mod 8, gun No. 161, a Mod 4 gun, a {{cvt|30|in}} muzzle liner and muzzle bell were used and the rifling was a uniform 1/25 instead of 0 to 1/35. Mod 9 was a Mod 4 using a tube constructed of [[nickel-steel]] instead of the normal gun-metal and again the rifling was a uniform 1/25. Mod 10 used a Mod 4 had a two-step cylindrical nickel-steel liner with the rifling changed to 0 to 1/25. Mod 11 used a Mod 4 but with only a one-step cylindrical nickel-steel liner and with a uniform 1/25 rifling. Mod 12 also used a Mod 4 with a nickel-steel liner and a 0 to 1/25 increasing twist rifling. The last Mod, Mod 13 consisted of a Mod 5 with a nickel-steel liner and the using an increasing twist rifling of 0 to 1/25.{{sfn|Navweaps|2015}}{{sfn|Friedman|2011|p=180}}
==Naval service==
{|class="wikitable"
!Ship
!Gun installed
!Gun mount
|-
|{{USS|Indiana|BB-1}}
|Mark 4: 6"/40 caliber
|Mark 5: 4 × central-pivot
|-
|{{USS|Massachusetts|BB-2}}
|Mark 4: 6"/40 caliber
|Mark 5: 4 × central-pivot
|-
|{{USS|Oregon|BB-3}}
|Mark 4: 6"/40 caliber
|Mark 5: 4 × central-pivot
|-
|{{USS|Illinois|BB-7}}
|Mark 4: 6"/40 caliber
|
* Mark 4: 14 × pedestal mount
* Mark 7: 14 × pedestal mount (refit by 1905)
|-
|{{USS|Alabama|BB-8}}
|Mark 4: 6"/40 caliber
|
* Mark 4: 14 × pedestal mount
* Mark 7: 14 × pedestal mount (refit by 1905)
|-
|{{USS|Wisconsin|BB-9}}
|Mark 4: 6"/40 caliber
|
* Mark 6: 14 × pedestal mount
* Mark 7: 14 × pedestal mount (refit by 1905)
|-
|{{USS|Cincinnati|C-7}}
|Mark 4: 6"/40 caliber
|Mark 6: 1 × pedestal mount
|-
|{{USS|Raleigh|C-8}}
|Mark 3: 6"/40 caliber
|Mark 6: 1 × pedestal mount
|}
==See also==
* [[6"/30 caliber gun]] – includes 6"/40 caliber Mark 3 guns
===Weapons of comparable role, performance and era===
* [[QF 6 inch /40 naval gun]] British equivalent
* [[15 cm SK L/40 naval gun]] German equivalent
==Notes==
{{Reflist|2}}
==References==
{{refbegin}}
* {{cite book
| first=Norman
| last=Friedman
| author-link=Norman Friedman
| url=https://books.google.com/books?id=yh3OAwAAQBAJ
| title=Naval Weapons of World War One
| publisher=Seaforth Publishing
| year=2011
| isbn=978-1-84832-100-7
}}
* {{cite web
|url=http://www.navweaps.com/Weapons/WNUS_6-30_mk1.htm
|title=United States of America 6"/30, 6"/35 and 6"/40 (15.2 cm) Marks 1, 2, 3, 4 and 7
|publisher=Navweaps
|date=3 May 2015
|access-date=15 May 2016
|ref={{sfnRef|Navweaps|2015}}
}}
{{refend}}
==External links==
{{Commons category}}
* [http://www.gwpda.org/naval/usn14gun.htm Bluejackets Manual, 1917, 4th revision: US Navy 14-inch Mark 1 gun]
{{WWIUSNavalWeapons}}
{{Use dmy dates|date=June 2017}}
{{DEFAULTSORT:6 40 Caliber Gun}}
[[Category:Naval guns of the United States]]
[[Category:152 mm artillery]]