 The M4 Sherman evolved from the M3 Medium Tank, which had its main armament in a side sponson mount.The M4 retained much of the previous mechanical design, but moved the main 75 mm gun into a fully traversing central turret.One feature, a one-axis gyrostabilizer, was not precise enough to allow firing when moving but did help keep the reticle on target, so that when the tank did stop to fire, the gun would be aimed in roughly the right direction.