verbal sinew
Usually the turret rotates slower than your head rotates as a fact. The game reduces sensitivity instead of create different scope mark on screen like in most tank simulators.
Different scope allows to implement turret stabilization feature (its not a point of design btw, idea originally is holding vertical degree while moving on uneven terrain and could be toggle on/off)
The feature currently unapplicable even for accidentally shaking mouse (1-2mm).
Same feature (toggle) would be a good addition for helicopters. Toggle "freeze" allowing to change seat (dangerous, vulnerable, you're not moving)
royal pagoda