Not quite what you see in the movies, some high velocity ammunition can penetrate the engine block of a car, pass through thick trees with ease, punch straight through brick walls and still retain the energy to penetrate a standard bullet vest.
To prevent penetration of military bullets, upgrade plates are used on top of NIJ Level IIIA armour. Plates are invariably supplied in 10 X 12 inch sizes for use in the front and rear upgrade pockets
An armour piercing bullet has a weight in excess of a one pound coin (£) and moves at nearly 2,000 miles per hour. It will not stop (in a practical distance), unless confronted by an area of exceptionally hard substance. The materials used to stop high energy bullets are invariably made of ceramics. We use substances that are similar to imitation diamonds to break the energy of such missiles. The ceramics are so hard that they can not be engineered or manipulated by any means available other than diamond or Boron Nitride cutting methods. An engineering workshop grindstone will be damaged if it touches our high level plates