Unlocking Orion isn’t the final grind in Modern Warfare 3, far from it. Every weapon has a mastery challenge for each mastery camo, requiring kills with that camo equipped. Unlike the camo grind we just covered, the weapon mastery challenges are far more straightforward. Weapon mastery challenges are the same for each weapon:
In other words, you must land 1,000 kills with 51 weapons in MW3 to finish the weapon mastery grind. This isn’t difficult but rather time-consuming, requiring you to frequently swap weapons and camos to make incremental progress. Completing all weapon mastery challenges grants some type of reward , but this reward is unknown as of the publication of this article. Some community members have speculated that camo mixing is the reward for this monumental grind, yet this hasn’t been confirmed or datamined.