Rules: Shots suffer no penalties when the archer’s mount is moving at a walk. If the mount is galloping, the penalty is only 4. Only lucky shots hit their mark when the mount is moving at a trot, requiring a 1 on 1D20 to hit, as usual (see page 242). Also, this SA allows the archer to fire to the rear while the mount is moving at a gallop.
Prerequisites: Mounted Combat
Combat Techniques: Bows, Crossbow, Thrown Weapons
AP Value: 10 adventure points
Publication: Core Rules page 248