A bullet's ability to injure is directly related to its kinetic energy at the moment of impact. Kinetic energy i.e. E = mv2 /2 The kinetic energy is directly propoional to weight (mass) of the bullet and the square of its velocity. Thus a bullet traveling at twice the speed of a second bullet of equal weight and similar size and shape, possesses four times much energy and injuring power. Ref: The Essentials of Forensic Medicine and Toxicology by Narayan Reddy, 27th edition, Page 189.