Manstopper
Manstopper is a generic term used to describe almost any combination of firearm and ammunition that can reliably be expected to incapacitate, or "stop" a human target immediately. For example, the .45 ACP pistol round and the .357 Magnum revolver round have a firm reputation as "manstoppers".
Historically, one type of ammunition has had the specific tradename "Manstopper". Officially known as the Mk III cartridge, these were made to suit the British Webley .455 service revolver in the early 20th century. The ammunition used a 220 grain cylindrical bullet with hemispherical depressions at both ends. The front acted as a hollow point deforming on impact while the base opened to seal the round in the barrel. It was introduced in 1898 for use against "savages," but fell quickly from favour due to concerns of breaching the Hague Conventions international laws on military ammunition, and was replaced in 1900 by re-issued Mk II pointed-bullet ammunition.
Some sporting arms are also referred to as "stoppers" or "stopping rifles". These powerful arms are often used by dangerous game hunters (or their guides) for stopping a suddenly-charging creature, like a buffalo or an elephant.
[edit] Stopping
Stopping power is a key concern for those who carry arms for self-defense, since an attack may occur suddenly and at close range, giving little time to act and stop the assailant. However, "stopping power" and the optimal means of achieving it are controversial subjects and an object of much terminal ballistics research and debate amongst firearms users and ammunition manufacturers.
Factors such as bullet mass, calibre, velocity and shape are all critical, but the location of shot is the most significant one. Shots that do not hit the central nervous system, cardiovascular system or major skeletal structures are unlikely to result in a successful "stop", even if they may eventually prove fatal.
