Prone Shooter

Combat

While prone, you use the ground to stabilize your aim while using a crossbow or firearm.

Prerequisite: Weapon Focus (crossbow or firearm), base attack bonus +1.

Benefit: If you have been prone since the end of your last turn, you can ignore the penalty the prone condition imposes on ranged attack rolls you make using a crossbow or firearm with which you have Weapon Focus.

Special: If you have the Prone Slinger feat, Weapon Focus (sling) satisfies this feat’s Weapon Focus prerequisite, and you can apply this feat’s benefit to attack rolls you make using a sling with which you have Weapon Focus.

Source: Ultimate Combat