The early problems with the German 120 mm Smoothbore made by Rheinmetall had led to the idea that it might not be ready at all. As a result, a secondary armament upgrade was considered, using an enhanced 105 mm gun in March 1983. This would have used a gun tube 1.5 metres longer than the tube of the M68A1 105 mm gun, and which could tolerate a much higher internal pressure. When the problems with the 120 mm XM256 were resolved, there was no need for this improved 105 mm gun and the plan for it was dropped for both the M1E1 and IPM1. The XM256 was accepted for use in December 1984, although into FY1985 there was still a validation trial of the improved 105 mm gun on an Abrams listed briefly as M1E2. Regardless of this 105 mm gun though the development life of the 105 mm rifled gun was essentially over, the new gun was clearly going to be the 120 mm smoothbore.