Cover Fire

Pick an ally when you roll initiative. When a creature would provoke an attack of opportunity from that ally or the ally would provoke an attack of opportunity from that creature, you may make an attack of opportunity with your ranged weapon just as if you were in melee range. This feat also acts the same as the sentinel feat, but for ranged weapons. 

• When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn.
• Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your ally's reach.
• When a creature within 5 feet of your ally makes an attack against a target other than your chosen ally (and that target doesn't have this feat), you can use your reaction to make a ranged weapon attack against the attacking creature.