Heavy Chainsword

If a model has the Shred special rule, or is attacking with a Melee weapon that has the Shred rule, it re-rolls failed To Wound rolls in close combat.

Similarly, if a model makes a Shooting Attack with a weapon that has the Shred rule, it re-rolls its failed To Wound rolls.

A model attacking with this weapon never receives +1 Attack for fighting with two Melee weapons (see page 177).