Really wish sniper rifles just bypassed sheilds if you use the right element. So tired of headshots not doing jack or taking 3 or 4 hits.
Precision damage does penetrate shields if the damage is sufficient to break the shield, you'll get the bonus on the remainder.
What I usually do with snipers is body shot a few times to weaken the shield with easy hits, then aim for the head on the shot that will break the shield to do precision damage and possibly stagger the target.