Missile Mastery skill
Missile Mastery gives you a bonus when using that kind of weapon - This is especially helpful during backtraining. The best way to train the Mastery skills is to train multiple weapons of that type. You can mind lock a Mastery skill using just one weapon, but you're better off training multiple weapons.
Spells and abilities that boost Missile Mastery
Spells and abilities that decrease Missile Mastery