16"/45 caliber Mark 1, 5, and 8
USS Colorado (BB-45), steams through rough seas, circa 1932, with her 16"/45 caliber gun turrets aimed to starboard.
Type	Naval gun
Place of origin	United States
Service history
In service	1921–1947
Used by	United States Navy
Wars	World War II
Production history
Designer	Bureau of Ordnance
Designed	Mark 1: 1913 Mark 5: 1935
Manufacturer	U.S. Naval Gun Factory Bethlehem Steel Watervliet Arsenal
Produced	1914–1920
No. built	Type Gun (45 cal): 1 (prototype) Mark 1: 40 (Gun Nos. 2–41)
Variants	Marks 1, 5, and 8
Specifications
Mass	230,948 lb (104,756 kg) (without breech) 235,796 lb (106,955 kg) (with breech)
Length	61 ft 4 in (18.69 m)
Barrel length	60 ft 0 in (18.29 m) bore (45 calibers)
Shell	AP Mark 3: 2,110 lb (960 kg) armor-piercing (AP) (Mark 1 gun) AP Mark 5: 2,240 lb (1,020 kg) AP (Mark 5 and 8 guns) HC Marks 13 and 14: 1,900 lb (860 kg) High explosive (HC) (Mark 5 and 8 guns)
Caliber	16 inches (406 mm)
Elevation	-4° to +30°
Traverse	300° max/280° min
Rate of fire	1.5 round per minute
Muzzle velocity	AP Mark 3: 2,600 ft/s (790 m/s) AP Mark 5: 2,520 ft/s (770 m/s) Full Charge HC Marks 13 and 14: 2,635 ft/s (803 m/s) Full Charge AP Mark 5: 1,935 ft/s (590 m/s) Reduced Charge HC Marks 13 and 14: 2,075 ft/s (632 m/s) Reduced Charge
Effective firing range	AP Mark 3: 22,900-yard (20,940 m) at 15° elevation AP Mark 5: 23,000-yard (21,031 m) at 15° elevation
Maximum firing range	AP Mark 3: 34,300-yard (31,364 m) at 30° elevation AP Mark 5: 35,000-yard (32,004 m) at 30° elevation

The 16"/45 caliber gun (spoken "sixteen-inch-forty-five-caliber") was used for the main batteries of the last class of Standard-type battleships for the United States Navy, the Colorado-class. These guns promised twice the muzzle energy over the Mark 7 12-inch/50 caliber guns of the Wyoming-class battleship and a 50% increase over the 14-inch/45 caliber guns of the New York-class, Nevada-class, and Pennsylvania-class battleships.^[1]

Design

The 16-inch gun was a built-up gun constructed in a length of 45 calibers. The Mark 1 had an A tube, jacket, liner, and seven hoops, four locking rings and a screw-box liner. When the gun was designed in August 1913 it was referred to as the "Type Gun (45 Cal.)" as an effort to conceal the gun's true size of 16 inches. Gun No. 1, the prototype, was proof fired in July 1914, less than a year after it was designed. After some minor changes the gun was re-proofed in May 1916 with production approved in January 1917, for Gun Nos. 2–41. Bethlehem Steel was given a contract for 20 guns and an additional 20 castings were ordered from Watervliet Arsenal for assembly at the US Naval Gun Factory at the Washington Navy Yard.^[1][2]

The Mark 1 guns were upgraded to Marks 5 and 8 in the late 1930s. The Mark 5s have a larger chamber to permit larger charges and a new liner with a heavier taper carbon steel along with a liner locking ring and locking collar. The Mark 8, similar to the Mark 5, had a uniform rifling with a chromium plated bore for increased life.^[1][3]

Naval service