16"/50 caliber Mark 2 gun

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16"/50 caliber Mark 2 Gun
South Dakota class battleships;H81481.jpg
16"/50 Mark 2 gun on display at the Washington Navy Yard.
Type Naval gun
Place of origin United States
Service history
In service 1924-47 as coastal artillery gun
Used by United States Navy, United States Army
Production history
Designed 1916
Manufacturer Naval Gun Factory, Bethlehem Steel, and others
Produced 1917-22
Variants Mod 0 and Mod 1
Weight 284,000 pounds (129,000 kg)
Length 816 inches (20.7 m) (without breech)
Barrel length 800 inches (20 m) bore (50 calibers)

Shell AP 2,240-pound (1,020 kg)
Caliber 16-inch (410 mm)
Recoil 49-inch (120 cm)
Elevation -4 to +40 degrees (turret), -7 to +65 degrees (casemate)
Traverse -145° to +145° (turret), 145° total (casemate)[1]
Rate of fire 2 rounds per minute
Muzzle velocity 2,800 feet per second (850 m/s)
Effective firing range 45,150 yd (41,290 m) on coast defense mount[2]

The 16"/50 caliber Mark 2 gun and the near-identical Mark 3 were guns originally designed and built for the United States Navy as the main armament for the South Dakota–class battleships and Lexington-class battlecruisers, neither of which was completed. At the time, they were among the heaviest guns built for use as naval artillery, though none of the ships designed for them were ever completed. They eventually served as the primary armament of the United States Army Coast Artillery Corps in CONUS in World War II.


Model of the South Dakota–class battleship, including 12 16"/50 Mark 2 guns.

The first example of a US 16-inch gun was an Army weapon, the M1895, approved for construction in 1895,[3] and completed in 1902; only one was built.[4] The first US Navy 16-inch gun was the 45 caliber Mark 1, which armed the Colorado-class battleships launched 1920-21.[5][6] The second Navy design, the Mark 2, was developed intended as armament for the planned South Dakota–class battleships, and also selected for the modified design of the Lexington-class battlecruisers, replacing the 14"/50 caliber gun that was originally used for the design.[7][8] The Mark 3 was a slightly modified version of the Mark 2.

With the United States entering into the Washington Naval Treaty, the terms limited the United States to a maximum displacement of 35,000 long tons (36,000 t). As both the South Dakota–class battleships and Lexington-class battlecruisers exceeded this limit, the Navy was required to cancel their construction, doing so in 1922.[9] While two of the Lexington class were re-ordered as Lexington-class aircraft carriers, none of them were completed with the barbettes necessary to mount these guns. Construction of the 16-inch Mark 2 and Mark 3 guns was also cancelled with approximately 70 completed. Twenty of the existing guns were transferred to the Army in 1922 and installed in coastal defense batteries to supplement the Army's more massive and much more expensive M1919 16 inch Coast Gun, of which only seven were ever deployed. The remaining Mk2/Mk3 guns were retained for use on future warships. With funding lacking until 1940, five batteries of two Mk2/Mk3 guns each were built 1924-40 in the harbor defenses of Pearl Harbor, the Panama Canal Zone (Pacific side), and San Francisco. They were designated 16-inch Navy MkIIMI and MkIIIMI in Army service. A version of the M1919 barbette mount used for the M1919 guns was used for these batteries.[10]

In 1938, with the signing of the Second London Naval Treaty, the tonnage limit for battleships was relaxed to 45,000 tons. After this, the U.S. Navy began design of a ship that would fit this higher tonnage limit, eventually resulting in the Iowa-class battleship. The larger size would allow for guns with a 16-inch caliber and a 50-caliber length, larger than the 16"/45 guns used on the North Carolina- and South Dakota-class battleships. While the Iowa-class battleships were under construction, the Bureau of Ordnance assumed that the guns to be used would be the existing Mark 2 design, and through miscommunication, the Bureau of Construction and Repair assumed the ships would use a lighter design. As a result, the Mark 2 and 3 guns were not used for these, and the 16"/50 caliber Mark 7 gun was designed instead.[11] The Mark 2 and 3 guns were never placed on any ship.

16-inch Navy MkIIMI gun on M1919 barbette mount in Panama.

With war on the horizon, the Navy released the approximately 50 remaining guns, and on 27 July 1940 the Army's Harbor Defense Board recommended the construction of 27 16-inch two-gun batteries to protect strategic points along the US coastline, to be casemated against air attack, as were almost all of the older batteries by this time. The M2 through M5 barbette mounts were used for the later batteries.[12] About 21 16-inch gun batteries were completed 1941-44, but not all of these were armed.[13]

Typical of this plan were the guns placed to protect Narragansett Bay, Rhode Island; two 16-inch guns were placed in Battery Gray, Fort Church, Little Compton, Rhode Island and two more were placed in Battery Hamilton, Fort Greene, Point Judith. A second battery of 16-inch guns at Fort Greene, Battery 109, had construction suspended in 1943 and never received guns. These batteries were placed such that they not only protected Narraganset Bay, but interdicted the main channels into Buzzards Bay and the east end of Long Island Sound.[14]

By late 1943, the threat of a naval attack on the United States had diminished, and with two or four 16-inch guns in most harbor defenses, construction and arming of further batteries was suspended. As 16-inch guns and a companion improved 6-inch gun were emplaced, older weapons were scrapped. With the war over in 1945, most of the remaining coast defense guns, including the recently-emplaced 16-inch weapons, were scrapped by 1948.


A casemated 16-inch gun. Almost all batteries were casemated by 1940.

These built-up guns were 66 feet 8 inches (20.32 m) long—50 times their 16-inch (406 mm) bore, or 50 calibers from breechface to muzzle. With a full powder charge of 648 pounds (294 kg), the guns were capable of firing a 2,240-pound (1,020 kg) armor-piercing shell with a muzzle velocity of 2,650 feet per second (810 m/s) firing out to an effective range of 44,680 yards (40,860 m).[3]

Surviving examples[edit]

See also[edit]


  1. ^ Berhow, p. 61
  2. ^ Berhow, p. 61
  3. ^ a b "16-inch Gun Technical Data". Archived from the original on 6 May 2009. Retrieved 4 April 2009. 
  4. ^ "Watervliet Arsenal Museum". Archived from the original on 4 April 2009. Retrieved 4 April 2009. 
  5. ^ DiGiulian, Tony, United States of America 16"/45 (40.6 cm) Mark 1
  6. ^ Friedman Battleships, p. 137
  7. ^ Friedman Battleships, pp. 154-165
  8. ^ Friedman Cruisers, pp. 86-103
  9. ^ "Navy Historical Center – Ship types: South Dakota Class". Archived from the original on 17 August 2010. Retrieved 3 September 2010. 
  10. ^ Berhow, pp. 174-175, 224
  11. ^ Friedman Battleships, pp. 311-313
  12. ^ Berhow, pp. 176-177
  13. ^ Berhow, p. 225
  14. ^ Walter K. Schroder (1980). Defenses of Narragansett Bay in World War II. Rhode Island Bicentennial Foundation. pp. 37–50. ISBN 0-917012-22-4. 
  15. ^ "16-Inch Coast Defense Gun". Retrieved 2007-06-18. 

External links[edit]