Tank gun
| M256 |
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 Front view of a M256 gun on an American M1A2 SEP main battle tank during a gunnery exercise at Red Cloud Range, 2013. |
| Type | Tank gun |
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| Place of origin | United States
Germany |
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| In service | 1985–present |
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| Designer | Rheinmetall, Watervliet Arsenal |
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| Manufacturer | Watervliet Arsenal |
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| Produced | 1985–present |
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| Variants | XM256, KM256, M256E1 |
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|
| Mass | 1,175 kg (2,590 lb) (gun tube)
1,905 kg (4,200 lb) (recoiling gun mass) |
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| Length | 5,593 mm (220.20 in) (overall) |
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| Barrel length | 5,300 mm (208.66 in) (gun tube) |
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|
| Shell | 120×570mm |
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| Calibre | 120 mm (4.724 in) |
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| Breech | semi-automatic vertical sliding-breechblock |
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| Recoil | 304.8 mm (12.000 in) |
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The M256 is an American 120 mm smoothbore tank gun. It uses a German-designed 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.
Origins
In January 1978, three years after the trilateral gun trials, the secretary of the army confirmed the service's choice of the Federal Republic of Germany for the XM-1.[1] The German Rh-120 smoothbore gun was to replace the 105 mm M68 tank gun in the Abrams and a license was obtained for its manufacture at Watervliet Arsenal at Watervliet, New York.[2] From October 1980 to September 1981, Watervliet Arsenal fabricated eight XM256 cannons and fourteen spare tubes.[3] During this same period, a product improvement program was underway to upgrade the basic M1 tank. On September 18, 1981, the Vice Chief of Staff of the Army directed that the project to install the new cannon, now designated as the 120mm gun XM256.
Technical characteristics
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.[4]
- The M256 features a cylinder-shaped cradle adapted to the recoil spring and Abrams gun rotor.
Variants
XM256
M256 designation when tested on the M1E1.
KM256
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
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.[5] 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.
