APx 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.
Lethal x Each time a friendly operative fights in combat or makes a shooting attack with this weapon, in the Roll Attack Dice step of that combat or shooting attack, your attack dice results of equal to or greater than x that are successful hits are critical hits. x is the number after the weapon's Lethal, e.g. Lethal 5+.
MWx Each time a friendly operative makes a shooting attack with this weapon, in the Roll Attack Dice step of that shooting attack, for each critical hit retained, inflict x mortal wounds on the target. x is the number after the weapon's MW, e.g. MW3.