The only thing to take into account is the angle of the windshield. A round such as a .38 Special or maybe even some rifle rounds may ricochet off the windshield if it hits at enough of an angle.
I watched this show where they showed that the only place you are really safe from incoming fire when taking cover behind a car is at the front or rear axles (behind the tires) since there is enough to stop the bullets there. But you should stand a few feet from the car so rounds hitting the hood or back won't fragment into you.
I hate how in movies and videogames they show car windshield shatter after being hit by rounds, even though the glass is layered and stuck together with special adhesive, so it would only spider a little bit.
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