The US prototype was equipped with a 152mm gun launcher with an auto loader. It was capable of firing AP/HE/WP rounds and the Shillelagh Missile. The main armament was to be a long-barrelled improved XM-150 variant of the XM-81 gun/launcher mounted on the M551 Sheridan and the M60a2 Patton. This was a much more reliable weapon than the earlier variant, firing Sabot, HE, and Cannister rounds in addition to the Shilelagh A/T Missile, but the earlier weapon's reputation was such that it was a lost cause from the start. It had a coax 7.62 machinegun and a 20mm AA remote control gun in a separate part of the turret. It would pop up out of twin hatches and fire at the target. The German version had a 120mm autocannon, instead of the 152mm gun launcher.
In some respects, the tank was fairly conventional. It had a diesel engine, and the armor, whilst strong was not of the composite type on the Abrams. The silhoutte was low. The tank had a three-man crew, each in his own compartment. Probably the most intruiging aspect was that all the crewmen were located in the turret. The driver was in the turret, in a capsule that rotated to keep him orientated to the front of the vehicle [it is said that the driver would often get confused when the turret rotated anyway]. This had the effect of raising the sihouette a little, and if the contra-rotating mechanism was knocked out, it would effectively immobilize the tank. It was to include hydropneumatic suspension, stabilization system, and a NBC system. The hydropneumatic suspension allowed the vehicle to crouch or raise one end of the tank to better take advantage of hull-down positions.
Problems, however, plagued the MBT-70 program from the beginning. Difficulties with English-German translations, metric to English measurement conversions, and differences between German and American manufacturing and designing practices caused considerable headaches before the first tanks were even designed. Most of the new systems were still experimental and this led to massive cost overruns and delays. Also the joint nature of the program led to disagreements about design features.