Phaeton Autocannon

If a model has the Rending special rule, or is attacking with a Melee weapon that has the Rending special rule, there is a chance that their close combat attacks will strike a critical blow. For each To Wound roll equal to or higher than the value listed, the target automatically suffers a Wound, regardless of its Toughness. The controlling player may choose to resolve these Wounds at AP 2 instead of the weapon’s normal AP value.
Similarly, if a model makes a Shooting Attack with a weapon that has the Rending special rule, a To Wound roll of equal to or greater than the listed value wounds automatically, regardless of Toughness, and is resolved at AP 2.
In either case, against Vehicles each Armour Penetration roll of equal to or greater than the listed value allows a further D3 to be rolled, with the result added to the total Strength of the attack. These Hits are not resolved at AP 2, but are instead resolved using the weapon’s AP value.
For example, a model with the Rending (5+) special rule that rolls To Wound against a non-Vehicle model will wound automatically on the roll of a 5+, and the attacking player has the choice of using an AP value of 2 instead of the AP value of their weapon.

Cover Saves and Damage Mitigation rolls granted by the Shrouded special rule cannot be taken against Wounds or Hull Point damage caused by weapons with the Ignores Cover special rule. This includes Cover Saves granted by Reactions and other special rules as well as Cover Saves conferred by terrain.

Attacks with this special rule may re-roll failed Armour Penetration rolls against Vehicles and Buildings (both with Shooting Attacks and in close combat) and re-roll Glancing Hits, in an attempt to instead get a Penetrating Hit, but the second result must be kept.