I have a video from a Federal Agency where they fired about 300 rounds of 9mm, .38,.357, .45, and 12 gauge buck at a sedan with two cardboard targets in it. They fired from dead ahead, and then from the left side, at about 10-15 feet.
1. Neither target had a hit on it.
2. They started up the car and drove it about 100 yards, flat tires, leaking fluids, and all.
Also, stop by a wrecking yard and check out what is inside a car door. It offers much more protection than a tee shirt.
But as noted the best thing to do is use the car to exit the kill zone!
Or, remember that a Ford at 30 MPH has more energy than the heaviest .500 S&W load - deadly force is deadly force.