YouTuber JerryRigEverything had a chance to fire some bullets at a bullet-proof car. The physics are interesting to watch as the energy disperses into the materials in slow motion.
Although they were invited down by the manufacturer, they say:
This is not a sponsored video. Its just super interesting to see how all of this technology works, and how Bullet proof cars are manufactured. There are several parts to a bullet proof car. The ballistic glass is pretty important. Its a layered slab of glass and plastic that stops the forward energy of the bullet.
Inside the metal paneling of your car are other bullet proof slabs. Some companies use heavy steel to block bullet penetration, but Armor Max uses a much lighter weight material that can even be used on bullet proof helicopters.