Attacks made with this special rule and Close Combat Attacks made by parts of models with this special rule impose a -X penalty on the enemy’s Armour Saves taken against them (in addition to the normal modifier from the Strength of the attack). If an attack has more than one instance of the Armour Piercing special rule, use the highest value available for
the attack. If the value within brackets is preceded by a “+” sign, add the existing value to already existing Armour Piercing value instead (if the model already had Armour Piercing). If not, use the value directly.