12-inch/50-caliber Mark 7 gun

12"/50 caliber Mark 5 Naval Gun
USS Arkansas (BB-33) firing her 12"/50 guns in battle practice prior to World War I
Type	Naval gun
Place of origin	United States
Service history
In service	1912-1952
Used by	United States Navy Argentine Navy
Wars	World War I World War II
Production history
Designer	Bureau of Ordnance
Designed	1910
Manufacturer	U.S. Naval Gun Factory Bethlehem Steel
No. built	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
Specifications
Mass	121,489 lb (55,106 kg) (without breech) 123,160 lb (55,860 kg) (with breech)
Length	50 ft 7.25 in (15.42 m)
Barrel length	49 ft 6.25 in (15.09 m) bore (49.5 calibers)
Shell	870 lb (390 kg)armor-piercing
Caliber	12 in (305 mm)
Elevation	-5° to +15°
Traverse	−150° to +150°
Rate of fire	2–3 rounds per minute
Muzzle velocity	2,900 ft/s (880 m/s) (full charge) 2,100 ft/s (640 m/s) (reduced charge)
Effective firing range	23,900 yd (21,900 m) at 15° elevation

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 Wyoming class of dreadnought battleships, the Mark 7 also armed the Argentine Navy's Rivadavia-class battleships.^[1][2]