06-13-2015, 09:44 PM
Mastery levels with a gun, say you like the shotgun specifically (Terran), the more people you kill with it the more mastery points you get, say once per level you get a perk with that gun (+1 Clip or +2% damage) some thing of that sort, it wouldnt be very major or game-changing but another fun thing to spend your no-life on.