If you are referring to the way they refract, it's pretty straightforward physics and you can train for it. If you're shooting outside at a target inside, your bullets will hit above your point of aim by a few inches, so you aim low. Vice versa from inside. Training, not intuition.
Roger that. If a dude is six feet or so in from you and draws down on you, aim for his pelvis (The more angled the windshield is the more dramatic this effect is. So, a Jeep windshield won't cause this marked shift of impact) The first round, maybe the second, will hit him in the sternum, most likely. Once you poke a hole the bullets will fly true. So, if you are shooting at a moving target and breaking glass each shoot, you've gotta aim low.
