Are weapon accessories unlocked on number of kills with that weapon or is it based on points awarded when that weapon is equipped?
On top of the kills per weapon, you also get some in the "Battle packs". Those are the bronze etc luggage that you get. You can open them in the loadout screen and find camos and accessories in them. The issue there is that the ones you find there are random and might be for a weapon that you did not even unlock yet.