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." 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." A license was obtained for its manufacture at
Watervliet Arsenal at
Watervliet, New York. From October 1980 to September 1981, Watervliet Arsenal fabricated eight XM256 cannons and fourteen spare tubes. 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. == Technical characteristics ==