Does Tactician work out the auxillary arc of a firespray? double the possible targets?

Yes it does. The auxilliary arc counts as a regular primary firing arc.

I'm pretty sure that an Auxiliary firing arc, like the one printed on the Firespray, does NOT count as a Primary arc.*

However, Tactician works because it simply says, "inside your firing arc," which covers all arcs.

* I could be 100% wrong, though.

I'm pretty sure that an Auxiliary firing arc, like the one printed on the Firespray, does NOT count as a Primary arc.*

However, Tactician works because it simply says, "inside your firing arc," which covers all arcs.

* I could be 100% wrong, though.

I think I've been slightly misunderstood when I said it "counts as" a primary firing arc. The confusion a lot of players seem to have stems from it being called the "auxiliary" arc, and that other than the official rules for it stating you can fire your primary weapon in this arc also, there's no other reference for it with regard to other game effects like Tactician, Backstabber, Outmaneuver (outside the FAQ). One of the most common questions is "is the auxiliary arc considered a firing arc for...?"

So when the OP asked if Tactician worked with the auxiliary arc, then the answer is yes, because it is still a valid firing arc, just like the primary arc is.

Yeah Tactician works, but secondary weapons don't (as per FAQ)