You should know this right off the bat: You can only get the XRK M4 Variant if you preordered Call of Duty: Modern Warfare. This M4A1 legendary blueprint was a preorder bonus as, as far as we can tell, is not available through any other means.

The M4 Carbine is a popular firearm in video games and a standard infantry weapon for the U.S. military, and many law enforcement agencies.