Knauf is declaring a BS attack against an enemy trooper. He'd like to leave a body to allow a classified to be done later in the turn. Can he waive the use of his BS Attack (shock) skill?
As I read those skills with modifiers like that, they are modifications to the skills themselves. I think the optional part is that you're not forced to declare BS Attack, but I think the MOD to the skill is just as mandatory to use if you use the skill as the gun's own ammo type or the full set of rules for the BS Attack skill. As a related topic, I don't think we've had any real confirmation if you're forced to use all available burst in N4 as the rules explanations for assigning burst has been shortened and simplified (as far as I can remember) which is highly important for units with BS Attack (+1B) and disposable weapons. Of course, I think it can be argued that BS Attack without MODs is available to all units and that Knauf (or e.g. Blue Wolf) should be able to declare a non-modded skill, but that still leaves the question about what happens when the MODs are on the guns. I think I'll just go ahead and add this to the list if I've not already got it there.
The "Skills and Equipment in Infinity" rule says, in one of its examples, "BS Attack (+1B) means that, when its user declares a BS Attack in their Active Turn, they must apply a +1 MOD to their BS Weapon’s Burst." [emphasis added]. Not definitive, but seems to be saying that the (+1B) is mandatory. If so, then presumably (Shock) would be mandatory as well. Another example in the rule says "BS Attack (Shock) means that the user adds Shock Ammunition to all their BS Attacks." [emphasis added]. Again not definitive, but "all" suggests that they can't make a BS Attack that doesn't add Shock Ammunition. The counterargument would be that all troopers have the Common Skill BS Attack (no mods), so Knauf can choose to use that skill rather than the Special Skill BS Attack (Shock). However, on that reading, an Azra'il would have to choose between the Common Skill BS Attack, the Special Skill BS Attack (+1 DAM), or the Special Skill BS Attack (Continuous Damage), and would not be able to shoot with +1 DAM and Continuous Damage at the same time. I think the intention is rather that the (+1 DAM) and (Continuous Damage) are both MODs to the Azra'il's Common Skill, so both can (and must) be applied in every shot. Consequently, I tentatively conclude that Knauf has the Common Skill BS Attack (Shock), and doesn't have the Common Skill BS Attack (no mods), so use of Shock is mandatory.
