The Best That Never Was 2 (Prototypes)

[The Dark]

There's always the venerable MBT-70. Intended to replace the M60 and Leopard 1, it was a joint German-American project armed with a longer-barreled (L/43.5) version of the 152mm gun/launcher used by the M60A2 and M551. It carried 42 rounds (some of which could be tungsten APFSDS), 6 Shillelagh missiles, 660 rounds of 20x139mm ammunition for an Rh 202 L/85 autocannon mounted on the turret roof, and 2700 rounds of 7.62x51mm for either an M73 (US) or MG-3 (German) machine gun. Top speed was 69 km/h, and 1300 liters of fuel was supposed to give it a range of ~645 kilometers.

One innovation was the use of spaced armor to disrupt HEAT warheads. I haven't found actual armor thicknesses, but estimated RHA equivalents (probably to be taken with an entire shaker of salt) are 101mm for the outer front hull and 152mm for the inner front hull, while the sides were 76-105mm (lower-upper), the mantlet around 450mm, the turret sides 63mm and 131 mm (outer and inner), and the turret rear 63mm.