Each time a friendly operative makes a shooting attack with this weapon, subtract x from the Defence of the target for that shooting attack. x is the number after the weapon's AP, e.g. AP1. If two different APx special rules would be in effect for a shooting attack, they are not cumulative - the attacker selects which one to use.
Each time a friendly operative makes a shooting attack with this weapon, in the Roll Attack Dice step of that shooting attack, for each attack dice result of 1 that is discarded, that operative suffers 3 mortal wounds.