Originally Posted by
Petit-Lion
When invoking momentum vs kinetic energy, keep in mind that the momentum rule only applies to non deformable solids. The firing gun and the fired bullet are essentially non deformable, and the gases have negligible mass, so the momentum rule applies to compute recoil.
When hitting the target, a lot of deformation occurs, and the kinetic energy is mostly converted into havoc and heat, so it's perfectly plausible that a well designed armor plate converts much of the kinetic energy into deformation of these fancy ceramics, leaving very little momentum (provided enough damping layers) to harm the wearer.
You may have my turn to test the armour, but do check your Life Insurance first.