So in a game last night, an Autarch ran up on his own to my immobilised Chaos Predator and planted a Haywire grenade on it, going for the Heavy Support VP in the 'big guns never tire' mission. The grenade was a dud, and with physical comic timing worthy of Buster Keaton, or at least Wile E. Coyote, the turret swivelled around and blew him in half with its autocannon. Probably with a sort of "mwah-mwah-mwah-mwaaaaaah..." trumpet effect.
The two-point VP swing for keeping my Predator and nailing his Warlord was irrelevant as it turned out - but while it was a very amusing image, should it have been allowed? Thing was, the barrel of the autocannon actually extended out past the Autarch - he was essentially behind the gun. I've since looked it up and the diagram in the rulebook says no, you can't shoot - so this is not a tournament question, and this thread is not in the rules forum. But I genuinely have no clue which ruling would have been the pedantic one and which would have been the sportsmanlike one.
Thing is, I don't know many people who are too fond of the idea that you are beholden to anything by the specifics of your miniatures' design, because that's the sort of thing that leads to modelling for advantage. If I had money and time to burn I could just have chopped off the end of my Predator's barrel there and then, for instance. It's nice to play in an environment where you can feel that people aren't going to be rewarded for that nonsense, even though the rules as written do precisely that, and part of that feeling means not punishing people for not doing it.
Bottom line, I have no idea whether I should have felt guilty or not.
So would it have been a rules lawyer or WYSIWYG nazi who said I couldn't fire, or a sly abuser of RAI who said I could..?