[@Alfhedil] The Mammoth tank incoporates not of C.E. technology. It has no shields, it's large to have thick armor and still have speed. We have Railguns, which are more powerful at destroying armor that your standard cannons. Oh, and missiles, lots and lots of missiles for those too fast vehicles and assault aircraft. On the ground, it's not the clones that are feared. A ground war with C.E. forces you to bring out anti-vehicle weaponry. And if you have enough vehicles to get C.E.'s Mammoth, well, there's only so many not only because they can't be mass produced, but because dozens aren't needed. 

This is all saying you don't have shields and not as thick armor as the Mammoth, and you don't out maneuver the gun. Keyguys Railguns are superior, but they aren't the lightest on the turret