Guesstimates? You never see them miss. Except in storms and presumably under cover of darkness were its actually more like prec 50 due to the halving.
Edit: Except were there are more than one unit in a square. Precision only narrows things down to a square. I once had a supercombatant that attacked a fort that contained a few weak astral mages. The astral mages were scripted to cast Horror Mark x5. But most of them missed because my SC was only size four and shared the square with and indy commander. Every spell hit that square but they all struck the poor indy commander instead of the SC. The SC did not get a single mark before he was finished with his long buff cycle.
