This spell permits an indirect fire siege engine to bombard its targets with greater accuracy, delivering more damage. The siege weapon receives a +1 enhancement bonus per four caster levels (maximum +5) on targeting rolls and damage rolls. If used on a direct fire siege weapon, this spell gives a weapon a +1 enhancement bonus per four caster levels (maximum +5) on attack and damage rolls. An enhancement bonus does not stack with a masterwork weapon's +1 bonus on attack rolls. This bonus does not allow a weapon to bypass damage reduction aside from magic.