8"/45 caliber gun

8"/45 caliber Mark 6

USS Rochester (CA-2), ex-USS New York (ACR-2), forward 8"/45 Mark 12 turret in 1932.
Type
Place of origin  United States
Service history
In service 1906
Used by  United States Navy
Wars World War I
Production history
Designer Bureau of Ordnance
Designed 1900
Manufacturer U.S. Naval Gun Factory
Variants Mark 6
Specifications
Weight 37,600 lb (17,100 kg)
Length 368 in (9.3 m)
Barrel length 360 in (9.1 m) bore (45 calibers)
Shell
Caliber 8 inches (203 mm)
Recoil 28.5 in (720 mm) max
Elevation
  • Marks 12:-7° to +20°
  • Marks 5:−7° to +20°
  • M1A1:−0° to +45°
Traverse
  • −135° to +135° naval mounts
  • 360° army M1A1 mount
Rate of fire 1 to 2 rounds per minute
Muzzle velocity
  • 2,750 ft/s (840 m/s) naval AP
  • 2,100 ft/s (640 m/s) army AP
  • 2,750 ft/s (840 m/s) army AP (super charge)
  • 2,150 ft/s (660 m/s) army HE
  • 2,840 ft/s (870 m/s) army HE (super charge)
Effective firing range
  • 22,500-yard (20,574 m) at 20.1° elevation
  • 35,300-yard (32,278 m) at 45° elevation (Army RR gun)

The 8"/45 caliber gun (spoken "eight-inch-forty-five--caliber") were used for the secondary batteries of the United States Navy's last pre-dreadnought battleships and refitted in older armored cruisers primary batteries.[1]

Design

The 8-inch/45 caliber gun was developed after the Spanish-American War to use the new smokeless powder that had recently been adopted by the Navy. This gun was much stronger than its predecessor, the 8"/40 caliber gun. The Mark 6 was constructed of tube, jacket, four hoops a locking ring and the liner with a Welin breech block. These were all constructed of nickel steel. There were a tolal of eight different Mods, Mark 6 Mod 0 to Mark 6 Mod 7, with different liners, breech mechanisms, chambers, and rifling being used.[1]

Service history

The guns mounted in the Virginia-class battleships were in an unusual two-level turret with the 8-inch guns on top of the larger 12-inch guns. This arrangement ultimately proved unsuccessful but helped the Navy in in the successful development of superfiring turrets later used in the dreadnought South Carolina.[1]

Due to an older 8"/40 caliber Mark 5's muzzle blowing off during gunnery practice on Colorado on 22 June 1907, all Mark 5's were removed from service, rebuilt, and placed in reserve. Because of this, all Pennsylvania-class armored cruisers and the armored cruiser New York, were refit with the newer Mark 6 guns.[2]

With the signing of the Washington Naval Treaty, the pre-dreadnoughts still in service were required to be scrapped. This surplussed about two dozen guns, which the Army used for coastal artillery, using new mountings and new lighter, and more streamlined, projectiles.[1]

Naval Service

Ship Gun Installed Gun Mount
USS Virginia (BB-13) Mark 6: 8"/45 caliber
  • Mark 12: 2 × twin turrets
  • Mark 5: 2 × dual-caliber turrets
USS Nebraska (BB-14) Mark 6: 8"/45 caliber
  • Mark 12: 2 × twin turrets
  • Mark 5: 2 × dual-caliber turrets
USS Georgia (BB-15) Mark 6: 8"/45 caliber
  • Mark 12: 2 × twin turrets
  • Mark 5: 2 × dual-caliber turrets
USS New Jersey (BB-16) Mark 6: 8"/45 caliber
  • Mark 12: 2 × twin turrets
  • Mark 5: 2 × dual-caliber turrets
USS Rhode Island (BB-17) Mark 6: 8"/45 caliber
  • Mark 12: 2 × twin turrets
  • Mark 5: 2 × dual-caliber turrets
USS Connecticut (BB-18) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS Louisiana (BB-19) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS Vermont (BB-20) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS Kansas (BB-21) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS Minnesota (BB-22) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS New Hampshire (BB-25) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS Mississippi (BB-23) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS Idaho (BB-24) Mark 6: 8"/45 caliber Mark 12: 4 × twin turrets
USS New York (ACR-2) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets
USS Pennsylvania (ACR-4) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets
USS West Virginia (ACR-5) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets
USS California (ACR-6) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets
USS Colorado (ACR-7) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets
USS Maryland (ACR-8) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets
USS South Dakota (ACR-9) Mark 6: 8"/45 caliber Mark 12: 2 × twin turrets

References

  1. 1 2 3 4 "United States of America 8"/45 (20.3 cm) Mark 6". Navweaps. 13 December 2008. Retrieved 5 May 2016.
  2. ↑ "United States of America 8"/35 (20.3 cm) Marks 3 and 4 8"/40 (20.3 cm) Mark 5". Navweaps. 12 March 2016. Retrieved 5 May 2016.

External links

Bluejackets Manual, 1917, 4th revision: US Navy 14-inch Mark 1 gun


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