But after that, there were disagreements. They differed on major elements like the main gun and engine, and even whether the design should use metric or SAE measurements. On this latter issue, they ultimately agreed to use both, which did nothing to contain the rising costs of the tank.
Instead of settling on one gun, they decided to both go with what they wanted, again causing the costs to skyrocket. The Germans chose a relatively simple, auto-loading, 120 mm Rheinmetall gun, while the Americans insisted on using the much more complex XM150 auto-loading, stabilized, laser rangefinder-equipped 152mm gun/launcher system, which, besides using an extensive variety of conventional tank rounds, could also fire the Shillelagh anti-tank missile.
Drawing of the MBT-70’s turret showing the driver’s rotating cupola and the 20 mm secondary armament in its stowed position. U.S. Army
The problem was, the American gun/launcher system never really worked. Variants of the system equipped the M551 Sheridan light reconnaissance vehicle and M60A1E2 tanks, but there were problems with the caseless 152 mm gun rounds, the overly complex Shillelagh missile, and the fire control and stabilization system. The extent of the problems with the M60A1E2 was such that most of the turrets were scrapped and the hulls re-equipped with turrets mounting conventional 105 mm cannon.
So many leading-edge technologies incorporated into the tank’s design, from the hydro-pneumatic suspension, laser rangefinder, ballistic computer and night vision system to the remotely-operated 20 mm anti-aircraft cannon and the 152 mm gun/launcher, meant there were problems making these new and complex systems work, and costs rose.
When the prototypes were built and testing started in 1968, both German and American contingents were pleased with the tank’s mobility. The German 120 mm gun also proved excellent, but the American XM150 continued to be problematic. As testing continued, they realized they had another big problem. Because the driver would be located inside a turret that would be rotating in battle, the tank’s designers had come up with the solution of mounting the driver inside his own contra-rotating cupola within the turret. Regardless of the direction the turret was facing, the cupola would automatically face forward. The drivers, however, accustomed to being located in a stationary position at the front of a tank’s hull, were becoming disoriented and suffering from motion sickness.
MBT-70 interior arrangement. The rotating driver’s cupola is partially obscured on the left side of the turret.
U.S. Army image
In the end, that was just one problem of several. So many leading-edge technologies incorporated into the tank’s design, from the hydro-pneumatic suspension, laser rangefinder, ballistic computer and night vision system to the remotely-operated 20 mm anti-aircraft cannon and the 152 mm gun/launcher, meant there were problems making these new and complex systems work, and costs rose.
They rose to roughly a million dollars a tank, five times the original estimated cost. By 1969, the Germans had pulled out of the program in favor of developing their own Leopard 2. Congress was also fed up. The Army tried placating them with a lower-cost system based on the same design, the XM803, but what they ended up with was an expensive version of the original M60. Congress cancelled the program at the end of 1971, and the Army plunged the remaining funds into development of what became the M1 Abrams the very next month.
The MBT-70 project was a massive failure, but many of the technologies that emerged from it were later perfected and employed in the M1 Abrams and West Germany’s subsequent Leopard II tank. A variant of the Germans’ 120 mm main gun, for example, equips the M1A1 and M1A2 Abrams today.
Since then no one has thought about jointly developing another tank.