Wikipedia

M256 (tank gun)

The M256 is an American 120 mm smoothbore tank gun. It is a licensed-built German-designed Rheinmetall Rh-120 L44 gun tube and combustible cartridges with an American-designed mount, cradle and recoil mechanism. It is primarily used by the M1 Abrams main battle tank.

M256
Front view of a M256 gun on an American M1A2 SEP main battle tank during a gunnery exercise at Red Cloud Range, 2013.
TypeTank gun
Place of originUnited States
Germany
Service history
In service1985–present
Production history
DesignerRheinmetall
Watervliet Arsenal
ManufacturerWatervliet Arsenal
Produced1985–present
VariantsXM256, KM256, M256E1
Specifications
Mass1,175 kg (2,590 lb) (gun tube)
1,905 kg (4,200 lb) (recoiling gun mass)
Length5,593 mm (220.20 in) (overall)
Barrel length5,300 mm (208.66 in) (gun tube)
Shell120×570mm
Calibre120 mm (4.724 in)
Breechsemi-automatic vertical sliding-breechblock
Recoil304.8 mm (12.000 in)

Origins

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A number of considerations had led the U.S. Army and its contractors to favor the Army's standard M68 105 mm gun over Germany's 120 mm Rheinmetall Rh-120 smoothbore gun for the XM1 Abrams. To begin with, the 105 mm gun was "the smallest, lightest, and least costly gun adequate for the job."[1] Indeed, new kinetic energy ammunition for the weapon then under development by the Army promised to extend the gun's usefulness well into the future. And because the Army's other tanks, the M60 and the upgraded M48, as well as the tanks of virtually every other NATO nation, used the 105 mm gun, mounting that gun on the XM1 promised to increase standardization within the alliance. Moreover, the continuing development of the new ammunition for the XM1 would in effect automatically upgrade every other gun in NATO. For all of these reasons, the XM1's development proceeded "on the assumption that the 105 mm gun would probably be the eventual main armament."[1][2] The tripartite British–American–German gun trials of 1975 produced a general agreement in the U.S. Defense Department that at some future point, a 120 mm gun of some design would be added to the XM1. Anticipating this, Chrysler and GM had both made changes to their tanks during development to make them compatible with a variety of main guns.[3] After head-to-head testing between the Royal Ordnance L11A5 and the Rheinmetall Rh-120,[citation needed] the Secretary of the Army announced in January 1978, that the Rheinmetall 120 mm gun would be mounted on future production versions of the XM1.[4] Although the L11/M256 120mm gun was chosen to be the main weapon of the Abrams in 1979, the improved ammunition for the gun still was not fully developed, thus delaying its fielding until 1984.[5] A license was obtained for its manufacture at Watervliet Arsenal at Watervliet, New York.[6] From October 1980 to September 1981, Watervliet Arsenal fabricated eight XM256 cannons and fourteen spare tubes.[7]

According to American tank historian Jim Warford, in retrospect, American intelligence underrated the effectiveness of Soviet armor. 105 mm guns were a poor match for Soviet tanks.[8]

Technical characteristics

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The M256 differs from the Rh-120 L44 in several aspects :

  • The M256 uses a concentric recoil spring instead of a separate buffer and recuperator hydraulic cylinders.[9]
  • The M256 features a cylinder-shaped cradle adapted to the recoil spring and Abrams gun rotor.

Variants

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XM256

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M256 designation when tested on the M1E1.

KM256

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Licence-produced variant of the US M256 gun for the Republic of Korea Army. Used on the South Korean variant of the K1A1 and K1A2.

M256E1

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To improve the lethality of the M1A2 main battle tank, the US Army funded the Advanced Tank Armament System (ATAS) research project to integrate a longer gun tube.[10] The long tube is based on the German Rh-120 L55 tube, made by Rheinmetall, and is 1.3 m longer than the conventional M256 120 mm gun tube.

Usage

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Operators

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Current operators

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Future operators

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See also

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References

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  1. ^ a b This is the testimony of Brigadier General Philip L. Bolte, Deputy Commanding General of the U.S. Army's Testing and Evaluation Command, before the Investigations Subcommittee of the House Committee on Armed Services in April 1978; Army Reprogramming Request No. 78-14 P/A, FRG Smooth Bore 120-MM Gun and XM-1 Tank, 95th Cong., 2d Sess., p. 30.
  2. ^ McNaugher 1981, p. 38.
  3. ^ McNaugher 1981, p. 40-45.
  4. ^ Information Spectrum 1983, p. B-7.
  5. ^ "Tank Munitions Development". Picatinny Arsenal. Archived from the original on June 18, 2020. Retrieved June 18, 2020.
  6. ^ Hunnicutt, R.P. Abrams: A History of the American Main Battle Tank, Vol. 2. Presidio Press. p. 221. ISBN 978-0891413882.
  7. ^ "Abrams Tank System". Office of the Program Manager (Annual Historical Review): 25. October 1, 1980.
  8. ^ "Q & A with Jim Warford about Soviet/Russian Armor". Tank and AFV News. March 25, 2015. Retrieved April 15, 2024.
  9. ^ Cooke, Gary W. "M256 120mm Smoothbore Gun". inetres.com. Retrieved May 6, 2023.
  10. ^ Cooke, Gary W. "M256 120mm Smoothbore Gun". inetres.com. Retrieved May 6, 2023.

Bibliography

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