"Many factors determine the severity of a wound, including a bullet’s mass, velocity and composition, and where it strikes. The AR-15, like the M4 and M16 rifles issued to American soldiers, shoots lightweight, high-speed bullets that can cause grievous bone and soft tissue wounds, in part by turning sideways, or “yawing,” when they hit a person. Surgeons say the weapons produce the same sort of horrific injuries seen on battlefields. Civilian owners of military-style weapons can also buy soft-nosed or hollow-point ammunition, often used for hunting, that lacks a full metal jacket and can expand and fragment on impact. Such bullets, which can cause wider wound channels, are proscribed in most military use."