The Me 262A-1/U1 differed from the standard A-1a in nose mounted armament. It featured two 20mm MG 151 cannon with 146 rounds each, two 30mm MK 103 cannon with 72 rounds each, and two 30mm MK 108 cannon with 66 rounds each. The MK 103 had a longer barrel and a higher muzzle velocity than the MK 108. The Me 262A-1a/U1 was an attempt to overcome the limitations of the usual quartet of 30mm MK 108 cannon. The MK 108 was prone to jamming and also had a low muzzle velocity. However the combination of three different cannon was also problematic and only three examples of the Me 262A-1a/U1 were built.