It appears as though the impacts that just barely puncture the metal actually do the most damage to the object, which I've always read and been told but never b

It appears as though the impacts that just barely puncture the metal actually do the most damage to the object, which I've always read and been told but never been able to visualize why. Think of the bullet as a packet of kinetic energy. When the bullet goes through, most of the energy goes through with it. Therefore, the damage to the object is relatively minimal (just a whole). When it is stopped, however, pretty much all the kinetic energy needs to be dispersed in the object itself. That happens via a number of mechanisms: deformation of the bullet, deformation of the surrounding material, heat, and, if the bullet breaks into pieces, of course, they can each take a chunk of energy with them as they go shooting in every direction.