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8-inch Mk.VI M3A2 railway gun
8-inch Mk.VI M3A2 railway gun
	8-inch Mk.VI M3A2 railway gun
Type	Railway gun
Place of origin	United States
Service history
In service	1941–1946
Used by	United States
Wars	World War II
Production history
Manufacturer	Baldwin Locomotive Works (railway carriage)
Produced	1941
No. built	32? railway version, 16 fixed barbette mounts
Specifications
Mass	tube and breech: 42,000 lb (19,000 kg); complete railway mount: 188,000 lb (85,000 kg)
Length	tube and breech: 30 ft 9 in (9.37 m)
Shell	separate loading HE and AP,; 260 pounds (120 kg) AP
Caliber	8 inches (203 mm)
Breech	Interrupted screw, step cut (Welin type)
Recoil	Hydro-pneumatic
Carriage	M1A1 railway
Elevation	45 degrees
Traverse	360 degrees
Rate of fire	2 rounds a minute
Muzzle velocity	2,750 ft/s (840 m/s) AP, or 2,840 ft/s (870 m/s) HE.
Maximum firing range	35,300 yd (32,300 m)
Feed system	hand

8-inch Navy MkVIM3 gun on barbette mount M1A1, as used by the Army in coast defense.

The 8-inch Navy gun Mk.VI M3A2 on railway mount M1A1 was a World War II improved replacement for the World War I-era 8-inch (203 mm) M1888 gun and was used by the US Army's Coast Artillery Corps in US harbor defenses. The guns were also mounted in fixed emplacements on the barbette carriage M1A1.^[1] These guns were US Navy surplus 8"/45 caliber guns from battleships scrapped under the 1922 Washington Naval Treaty. Mark VI (also Mark 6) was the Navy designation. The Army designation for this gun was "8-inch Navy gun Mk.VI M3A2".^[1]

History

The ex-Navy Mark VI railway gun was quickly put together at the start of World War II, to supplement the older World War I 8-inch M1888 railway gun. It was developed from an experimental 12-inch (305 mm) railway howitzer carriage of World War I.^[3] The all-around rotating mount and outriggers were designed to allow the gun to track a moving target for coast defense. These guns had a very short life in Army use, entering service in February 1941 and being cut up for scrap immediately after the war. The guns were the Navy's 8-inch (203 mm)/45 caliber Mark VI, and were originally secondary armament on Virginia- and Connecticut-class battleships launched 1904-06 and scrapped in the 1920s.^[4] They were mounted in both fixed emplacements and on the M1A1 railway carriage.^[1]

Deployment

Fixed two-gun batteries at Fort Church (Narragansett Bay, Rhode Island), Fort Rosecrans (San Diego, California), Fort Ruger and two other locations (Oahu, Hawaii) (two not completed), Fort Schwatka (Dutch Harbor, Alaska), Fort J. H. Smith and Fort Abercrombie (Kodiak, Alaska), Fort Segarra near St. Thomas in the United States Virgin Islands, and Roosevelt Roads, Puerto Rico (not armed).^[5]
Railway guns: 8 at Fort Miles, Delaware, two 4-gun batteries each in the Los Angeles and Puget Sound harbor defenses and Fort John Custis near Cape Charles, Virginia, others at Fort Hancock, New Jersey (near New York City).^[1]^[6]^[7]

Sighting and fire control equipment

The following sighting equipment was used with the gun.

M1 Deflection board
M1 fire adjustment board
M1A1 Range correction board
M3 Spotting board
M1912 Clinometer
M1 Percentage corrector
M1A1 Height finder, or M2A1
M6 Azmuth indicator
M5 Elevation indicator
M1910A1 Azmuth instrument
M8 Helium filling kit
M1 Gunners quadrant
Type B, set forward rule
M1 prediction scale
bore site
firing table, 8-I-1.^[8]
M7 stereoscopic trainer
M1 generating unit

Support cars

M2 fire control car
M1 machine shop car
modified box car for ammunition

Surviving Examples

Four weapons of this type survive:^[9]

One gun at Fort Miles, Delaware, on M1 railway proof mount (experimentally bored out to 9.12 in (232 mm)) (was previously at Naval Surface Warfare Center Dahlgren Division, Dahlgren, VA^[10]
Two 8-inch Guns Mk VI M3A2 (#160L2 & #154L2), Battery 404, Fort Abercrombie, Kodiak, AK
One 8-inch Gun Mk VI M3A2 (#134L2), Kodiak Airport, Kodiak, AK (gun formerly at Battery 403, Fort J.H. Smith, Kodiak, AK)

References

^ ^a ^b ^c ^d ^e ^f Berhow 2004, pp. 114–117.
^ ^a ^b Berhow 2004, p. 61.
^ Lewis 1979, p. 109.
^ "USA 8"/45 (20.3 cm) Mark 6". NavWeaps.com.
^ Berhow 2004, p. 226.
^ Lewis 1979, pp. 140–141.
^ Gaines, William C., Coast Artillery Organizational History, 1917-1950, Coast Defense Journal, vol. 23, issue 2, pp. 6-8, 25-27
^ "FT 8-I-1 Firing tables". Gene Slovers US Navy Pages.
^ Berhow 2004, p. 234
^ "Railway Batteries". FortMiles.org. Archived from the original on 28 September 2018. Retrieved 7 November 2012.

TM 9-2300 Standard Artillery and Fire Control Material. 1944.^{[full citation needed]}
"TM 9-463" (PDF).^{[full citation needed]}
SNL E-34^{[full citation needed]}
"FM 4-49" (PDF). Archived from the original (PDF) on 19 December 2010. Retrieved 27 August 2010.^{[full citation needed]}
Berhow, Mark A., ed. (2004). American Seacoast Defenses, A Reference Guide (second ed.). CDSG Press. ISBN 0-9748167-0-1.
Lewis, Emanuel Raymond (1979). Seacoast Fortifications of the United States. Annapolis, Maryland: Leeward Publications. ISBN 978-0-929521-11-4.