Call of Duty – Black Ops 2: How to Unlock Attachments
In Black Ops 2, attachments work a little differently than most of the previous games.
Each gun starts with no available attachments, and each gun has to be leveled up separately.
Unlocking attachments is just a matter of using the gun enough to level it up.
I kind of like this in a way, because it means you can’t just throw the best attachments at a weapon and go to town, you have to use it and get experience with it.