Cavitation refers to the creation of a cavity inside the target. Bullets can force tissue away from the sides of its path, as seen in this clay model. Note the small size of the entry and exit holes. Bullets produce tissue damage in a few different ways, including Laceration and crushing - Low velocity bullets, like those fired by handguns, travel less than 300 metres per second and do almost all their damage through crushing. Cavitation happens at more than 300 metres per second.
Shock waves compress the tissues and travel ahead and to the sides of the bullet.
They last only a few microseconds and don't cause much harm at low velocity, but at high velocity they can generate shock waves can reach up to 200 atmospheres of pressure. Shock waves can burst fluid-filled organs such as the heart or spleen. Distance plays a role in how much wounding will occur. Most bullets fired from handguns have lost a significant amount of KE at 100 metres, while high-velocity military rounds still have a good proportion of KE at 500 metres. Military and hunting rifles are designed to deliver bullets with more KE at a greater distance than handguns and shotguns.