US variant built in 1980 Cannon, 105mm Gun: M68A1E2 MIL-C-45504A Rev. D Jan 1987 Military and Government Specs & Standards (Naval Publications and Form Center) (NPFC) for use on the M1 and IPM1 versions of the M1 Abrams MBT M1 Abrams in Action By Jim Mesko – 1996 Squadron/Signal publications fitted with a 1 feet longer (total length 236.5 inches) XM24E4/L55 gun tube and re-enforced breach Cannon, 105mm Gun: M68A1E2 MIL-C-45504A Rev. D Jan 1987