I believe that the crown knights have no chance against the orcs due to vastly superior orc technology. Orc technology is more than a thousand years ahead of the crownies. You can see this in the MM recon dropship's use of the same projectile employed by the troll battle wheel.
One can only conclude that leftover orc missiles were found, and employed by the MM team due to their vastly superior quality, even at that future time.