Bullets from a variety of guns. Injury depends on how much force is applied over how much area to what kind of tissue.
Entrance wound characteristically small and round if no deflection by rib.
Disruption of the tissue with hemorrhage. Exit wounds much larger with more ragged edges. Course dependent on size of vessel lacerated, other injuries, and the speed at which help is obtained. Lung heals well if kept expanded. Robbins Pathologic Basis of Disease.