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
Effective Skill Formula
Reverse engineering has been performed on years of game data and determined that the effective weapon ranks with regards to mastery use this formula:
(.75 * weapon ranks) + (.25 * mastery skill) = effective weapon ranks
- NOTE: This is a base formula, and does not account for the bonuses provided to the character from stats, buffs, and bonuses.