You can however just make the turret not turnable and add a "AcceptableAimDelta" to the weapon you want that turret to fire. With that you can still make the turret not moveable but the weapon will still fire at some target within the aim delta's range.
lol, I've been wondering about something similar but not the same. I've been thinking about weapons that will only fire in three distinct directions from certain points on a model, namely the two sides and the front. Would it be possible to make it do so in anyones opinion?
It's certainly something that runs high on my 'things to get working' list.
This may be beating a dead horse but I've looked, I've tried, I've bashed my head on my keyboard. Its not possible. The closest thing is the AcceptableAimDelta mentioned below.