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.

"[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.

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.

Anticipating this, Chrysler and GM had both made changes to their tanks during development to make them compatible with a variety of main guns.

[6] From October 1980 to September 1981, Watervliet Arsenal fabricated eight XM256 cannons and fourteen spare tubes.