One of the terms that is often mentioned in discussions of this sort is "stopping power". It is defined as the ability of the cartridge to cause enough ballistic injury to incapacitate a target where it stands. The physical characteristics of the bullet, the type of target and the shot placement has a large effect on stopping power. For example, a bullet capable of stopping a human will not stop a charging cape buffalo, a grazing shot will not have as much effect as a hit to center of mass etc.
Some of the methods used to measure cartridge performance include:
- Kinetic energy - This is a scientific method and is often used by cartridge manufacturers to tout the superiority of their products.
- Momentum - Another scientific method that is sometimes used by cartridge manufacturers
- Taylor KO Factor - This is an empirical formula devised by John (Pondoro) Taylor, a 20th century big game hunter and poacher in Africa.
- Thorniley Stopping Power Formula - Another empirical formula, devised by Peter Thorniley, who is another big game hunter in North America and Africa.
- Hatcher Formula - Developed by Major General Julian Hatcher of the US Army in the 1930s, to determine the effectiveness of various types of pistol ammunition.
- Optimum Game Weight Formula - Developed by Edward A. Matunas and first appeared in the April 1992 issue of Guns magazine.
Some of these methods (such as kinetic energy and momentum) ignore the diameter of the bullet and some of the others formulae take the size of the bullet into consideration. Only one of these methods (Hatcher formula) considers the construction of the bullet (e.g. an expanding bullet may be more effective than a non-expanding one) and the shape of the bullet (e.g. a solid wide nose bullet vs. a round nosed one) to be factors in performance, the others don't consider these factors as important at all. However, they all do help in simplifying some of the details of bullet effectiveness.
We will study these methods in detail in the following days.