12-inch/40-caliber gun

12"/40 caliber Mark 3 and Mark 4
12"/40 guns of the ship's forward gun turret, photographed circa 1907-1908. Note Sailors strolling on deck; bell mounted on the pilothouse face; and 3-pounder guns mounted on the superstructure.
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
  • Mark 4: −3° to +15°
  • Mark 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

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]

  1. ^ Navweaps 2016.