Astartes Grenade Launcher

Weapons with [BLAST] in their profile are known as Blast weapons, and they make a random number of attacks. Each time you determine how many attacks are made with a Blast weapon, add 1 to the result for every five models that were in the target unit when you selected it as the target (rounding down). Blast weapons can never be used to make attacks against a unit that is within Engagement Range of one or more units from the attacking model’s army (including its own unit).