Even handguns will do a number against an unarmored vehicle.
What happens will likely surprise you.
Watch the video below:
Very surprising penetration from Full Metal Jacket pistol rounds, being able to travel, in most cases, right through the front seats. A Glock 43 sure can spit out the 9mm rounds.
This is exactly why law enforcement and military wear body armor in what is termed "soft-skinned vehicles," tactical speak for unarmored everyday trucks, vans and cars.
Modern firearms, especially rifles, with FMJ or armored piercing rounds will make Swiss cheese of any normal vehicle, so there is no real protection from hiding behind car doors or side panels.
The only thing that may provide some level of protection is a big engine block. In many tactical training courses, it's actually taught to get away from your vehicle if it's immobile due to enemy fire.
This demonstration is always good to keep in mind, though, as you never know when you'll have to take cover in an emergency situation.