14-inch M1920 railway gun

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14-inch M1920 railway gun
Diagram showing gun barrel in the elevated position.
Type	Railway gun
Place of origin	United States
Service history
In service	1925–1946
Used by	United States
Wars	World War II
Production history
Designed	1920
Manufacturer	Watervliet Arsenal
Produced	1925
No. built	4
Specifications
Mass	Tube and recoil band: 230,000 lbs
Length	18.1 meters (60 feet)
Shell	Separate loading, HE, and AP
Caliber	14-inch (355.6 mm)
Breech	Interrupted screw, (step-cut)
Recoil	Hydro-pneumatic
Carriage	Railway truck, 14 axles
Elevation	50° fixed, 19° on track
Traverse	7° on track, 360° fixed
Rate of fire	1 rpm
Muzzle velocity	2,650 feet per second (808 m/s)
Effective firing range	48,220 yards (44,090 m)
Feed system	Hand

The 14-inch M1920 railway gun was the last model railway gun to be deployed by the United States Army. It was an upgrade of the US Navy 14"/50 caliber railway gun. Only four were deployed; two in the Harbor Defenses of Los Angeles and two in the Panama Canal Zone, where they could be shifted between the harbor defenses of Cristobal (Atlantic) or Balboa (Pacific).

After the close of World War I, the US Army wanted to incorporate the lessons learned from other railway gun mounts and fulfill coastal artillery requirements for hitting a moving target. An effort to design a more universal mount for the Navy's Mk. IV 14"/50 caliber gun was undertaken.^{[citation needed]}

The primary difference from the earlier Navy versions lies in the M1920 carriage, which could be raised and lowered. Prepositioned fixed mounts were installed at the forts, and the gun's rail trucks could be taken out from under the frame. After the removal of the rail trucks, the gun was lowered and bolted onto a pivot point for rapid 360 degree movement, necessary for tracking ships in coast defense. The M1920 carriage made the gun much more flexible. It allowed for the standard practice of using a curved piece of rail to traverse the gun, and it enabled the gun to be used in a fixed position.^[1]

Two guns were deployed to Fort MacArthur in the Harbor Defenses of Los Angeles, with firing platforms at Fort MacArthur and Long Beach. The remaining two guns were deployed to Fort Grant and Fort Randolph in the Panama Canal Zone. The two guns deployed to the Panama Canal Zone could be moved to either coast on the Panama Canal Railway. After World War Two ended, the threat of a massive war was over and the United States scrapped these weapons as well.^[2]

The Mk.IV gun was manufactured in two models:

• M1920MI centerline of breechblock mechanism canted 16 degrees counterclockwise to fit recoil band
• M1920MII breech mechanism is set straight in relation to axis of tube.

The following sighting equipment was used with the gun:

• bore sight
• firing tables- 14-m-1, 14-e-3, 14-g-2.
• M1 fire adjustment board
• M1 generating unit (mounted on the forward railway truck)
• M1 gunners quadrant
• M1 plotting and relocating board
• M1 prediction scale
• M1A1 height finder
• M1A1 range correction board
• M7 spotting board
• M8 helium filling kit
• M1910 azimuth instrument
• M1912A1 clinometer
• M1917MI panoramic telescope
• M1918 aiming rule
• M1922 panoramic telescope

• M1 powder car
• M1 projectile car
• M2 fire control car
• M1918 repair car

All four guns were cut up for scrap in 1946.

• 
  A M1920 on the test range.
• 
  A M1920 on the test range.
• 
  A group photo with a M1920.

• 14"/50 caliber railway gun US World War I predecessor
• Angular mil
• Coast Artillery fire control system
• Coincidence rangefinder
• Gun laying
• Indirect fire
• List of U.S. Army weapons by supply catalog designation
• Railway gun
• Sound ranging

Wikimedia Commons has media related to 14-inch M1920 railway gun.

• Berhow, Mark A., ed. (2004). American Seacoast Defenses, A Reference Guide (Second ed.). CDSG Press. ISBN 0-9748167-0-1.
• McGovern, Terrance and Smith, Bolling, American Coastal Defences 1885–1950 (Fortress series, Book 44), Osprey Publishing 2006, ISBN 1-8417692-2-3
• Military Railroads on the Panama Canal Zone by Charles S. Small, Railroad monographs 1982
• Miller, H. W. (1921). Railway Artillery. Vol. II. Washington: US Government Printing Office. pp. 169–186. (Vol. I at this link)
• J. C. Letts, Walker Redmon: Heavy Railway Artillery Transportation. in: The Military Engineer. Vol. 18, No. 100, 1926, OCLC 7852953789, p. 268–269
• TM 9-2300 Standard Artillery and Fire Control Material. dated 1944
• FM 4-35 Service of the Piece; 14-inch Gun, M1920MII on Railway Mount, M1920 (1940)
• SNL E-9
• SNL E-33
• Coast Artillery Journal December 1929
• American Coast Artillery Materiel 1922 [1] (extensive manufacturing information)
• Coast Artillery Journal March April 1934

• "Gun Train Guards Ends of Panama Canal -- Rolling Fort Crosses Isthmus in Two Hours" Popular Mechanics, December 1934 pp.844-845 excellent drawings in article
• FortWiki gun type list