as per the FAQ, war machines are permitted to swivel in the shooting phase to face their target. Does this apply to Stegadons?
No. Yes. The beast no. The bolt thrower mounted on top? Yes. Unlesss there are specific, explicit rules, on the Steg’s warscroll that state that the arc of fire for the bolt thrower has limits. Nose of beast = does not move. Bolt thrower = spins. Tuppence. 2 ¢
I think the main point is that at the beginning of the BRB section on war machines, it says to check what category of troop you have. Stegs are (unfortunately) monsters, so aren't subject to the war machine rules.