12"/40 caliber gun

The 12"/40 caliber gun (spoken as "twelve-inch-forty--caliber") were used for the primary batteries of the United States Navy's last class of monitors and the Maine-class and Virginia-class pre-dreadnought battleships.[1]

12"/40 caliber Mark 3 and Mark 4
View of Ohio and her forward 12"/40 caliber guns in the Mark 4 turret in 1916.
TypeNaval gun
Place of originUnited States
Service history
In service1902
Used byUnited States Navy
WarsWorld War I
Production history
DesignerBureau of Ordnance
Designed1899
ManufacturerU.S. Naval Gun Factory
No. built
  • Mark 3: 41 (Nos. 15–41, 50–56)
  • Mark 4: 10 (Nos. 49, 58–60, 150–154, 179)
VariantsMark 3 and Mark 4
Specifications
Mass
  • 116,480 lb (52,830 kg) (with breech)
  • 114,960 lb (52,140 kg) (without breech)
Barrel length40 ft 0 in (12.19 m) bore (40 calibers)
Shell870 lb (390 kg) armor-piercing
Caliber12 in (305 mm)
Elevation
  • Marks 4:-3° to +15°
  • Marks 5:−7° to +20°
Traverse−150° to +150°
Rate of fire
  • 0.66 rounds per minute (as commissioned)
  • 2 rounds per minute (after 1906)
Muzzle velocity
  • 2,800 ft/s (850 m/s) (as commissioned)
  • 2,600 ft/s (790 m/s) (first derating)
  • 2,400 ft/s (730 m/s) (final derating)
Effective firing range19,000 yd (17,374 m) at 15.5° elevation

Design

The 12-inch (305 mm)/40 caliber gun was developed after the Spanish–American War to use the new smokeless powder that had recently been adopted by the Navy. The Mark 3, gun Nos. 15–48 and 50–56, was constructed of tube, jacket, and eight hoops. It was found that the early guns suffered from excessive bore erosion, in an attempt to fix this the Navy reduced the propellant charges to reduce the muzzle velocity, because of this the Mark 4, gun Nos. 49, 58–60, 150–154, and 179, was similar to the Mark 3 but with a smaller chamber for the reduced propellant charge.[1][2]

Service history

The guns mounted in the Virginia-class battleships were in an unusual two-level turret with the 8-inch (203 mm)/45 caliber guns on top of the larger 12-inch guns. This arrangement ultimately proved unsuccessful but helped the Navy in the successful development of superfiring turrets later used in the dreadnought South Carolina.[1]

Incident

Gun No. 49, while testing powder at the Naval Proving Ground, had the entire muzzle and chase blow off. The board appointed to investigate came to the conclusion that the new powder, while performing properly, caused a pressure along the chase that was dangerously close to the strength curve. It was decided that when the guns were withdrawn to be relined they would add an additional hoop that extended to the muzzle would be places on the chase.[3]

Ship Gun Installed Gun Mount
USS Arkansas (BM-7) Mark 3 or 4: 12"/40 caliber Mark 4: 1 × twin turrets
USS Nevada (BM-8) Mark 3 or 4: 12"/40 caliber Mark 4: 1 × twin turrets
USS Florida (BM-9) Mark 3 or 4: 12"/40 caliber Mark 4: 1 × twin turrets
USS Wyoming (BM-10) Mark 3 or 4: 12"/40 caliber Mark 4: 1 × twin turrets
USS Maine (BB-10) Mark 3 or 4: 12"/40 caliber Mark 4: 2 × twin turrets
USS Missouri (BB-11) Mark 3 or 4: 12"/40 caliber Mark 4: 2 × twin turrets
USS Ohio (BB-12) Mark 3 or 4: 12"/40 caliber Mark 4: 2 × twin turrets
USS Virginia (BB-13) Mark 3 or 4: 12"/40 caliber Mark 5: 2 × dual-caliber turrets
USS Nebraska (BB-14) Mark 3 or 4: 12"/40 caliber Mark 5: 2 × dual-caliber turrets
USS Georgia (BB-15) Mark 3 or 4: 12"/40 caliber Mark 5: 2 × dual-caliber turrets
USS New Jersey (BB-16) Mark 3 or 4: 12"/40 caliber Mark 5: 2 × dual-caliber turrets
USS Rhode Island (BB-17) Mark 3 or 4: 12"/40 caliber Mark 5: 2 × dual-caliber turrets

Notes
  1. Navweaps 2016.
  2. Friedman 2011.
  3. Mason 1905, p. 14.
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References
Books
  • Friedman, Norman (2011). Naval Weapons of World War One. Seaforth Publishing. ISBN 978 1 84832 100 7.CS1 maint: ref=harv (link)
  • Mason, Newton E. (1 October 1905). Report of the Chief of the Bureau of Ordnance to the Secretary of the Navy. Washington, D.C.: Government Printing Office. Retrieved 13 October 2016.CS1 maint: ref=harv (link)
Online sources

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