You can make devastating attacks with ranged weapons against charging opponents.
Prerequisite: Point Blank Shot.
Benefit: You can ready an action to fire a ranged weapon at a foe who charges you. You must wait until the target is within 15 feet before you attack. If you score a hit with this readied attack, your attack deals an extra 3d6 points of damage. Creatures immune to extra damage from critical hits are immune to this effect.
Source: Heroes of Battle, page 99.