Great bows follow the rules for Bolt Throwers with Strength 5, Armour Piercing (1) and Multiple Wounds (D3) special rules.
Source: Warhammer Armies Project: Unofficial 9th Edition (v2.2)
Great bows follow the rules for Bolt Throwers with Strength 5, Armour Piercing (1) and Multiple Wounds (D3) special rules.