Orion is the final mastery camo in Modern Warfare 3, and in order to unlock the camo, you need to first unlock Polyatomic on at least 51 weapons. There are no additional challenges to complete here, as Orion is automatically unlocked for all 51 of those weapons with the Polyatomic camo earned.
This is a much more simplified version of the mastery camo challenge grind that we’ve seen in recent years, so this shouldn’t be a huge struggle to reach the Orion camos.
Yes.
All Weapon Camos will carry forward into Modern Warfare III. Limited-time Event Camos that were available only during a certain period are accessible if you unlocked them in Modern Warfare II at that time.
Example: A MWII player has an M4 with “Orion” Mastery Camo unlocked (above). They can equip the weapon, and the Camo, and any other unlocked Camos in MWIII. Note you can’t equip the “Orion” Camo to a MWIII weapon.