Even when a bullet is stopped by body armor, the wearer is not immune to injury. The transfer of kinetic energy can cause Back Face Signature (BFS) or Blunt Force Trauma (BFT), resulting in severe internal injuries like organ damage or broken ribs. Modern armor standards, such as those from the NIJ, strictly limit the allowable depth of this deformation during certification testing.
Manufacturers combat BFT through advanced materials that better dissipate energy and designs that increase the surface area over which the force is distributed. Understanding BFT is critical for medical personnel and operators, highlighting that surviving a shot is not just about stopping penetration but also managing the devastating energy transfer.
