An experimental study of bullet mass and velocity and their relation to fracture patterns in flat bones

This study investigated relationships between bullet mass, velocity, kinetic energy (KE), and fracture propagation in flat bones. Sixty full metal jacketed 9-mm bullets of different masses were fired at pig (Sus scrofa) scapulae. A chronograph measured bullet velocity prior to impact. Fracture characteristics were documented using standard terminology, counted, and measured at the entrance aspect, exit aspect, and overall per specimen. Few significant relationships between ballistic and fracture variables were found across the ranges tested, suggesting possible threshold effects. Bullet mass influenced velocity, suggesting that KE is the most practical variable for interpreting trauma in forensic contexts. Side-specific analyses showed entrance fracture length was primarily driven by long individual radial cracks, while exit fracture length reflected more cracks, more diverse crack types, and longer individual cracks. These findings provide a baseline for future research and underscore the utility of a standardized, quantitative, and surface-specific framework for documenting fracture characteristics.