Stopping Power

Stopping power is the ability of a firearm or other weapon to cause a penetrating ballistic injury to a target (human or animal) enough to incapacitate the target where it stands. This contrasts with lethality in that it pertains only to a weapon's ability to incapacitate quickly, regardless of whether death ultimately ensues. Some theories of stopping power involve concepts such as "energy transfer" and "hydrostatic shock", although there is disagreement regarding the importance of these effects.

Stopping power is related to the physical properties of the bullet and the effect it has on its target, but the issue is complicated and not easily studied. Critics contend that the importance of "one-shot stop" statistics is overstated, pointing out that most gun encounters do not involve a "shoot once and see how the target reacts" situation.

Stopping is usually caused not by the force of the bullet (especially in the case of handgun and rifle bullets), but by the damaging effects of the bullet, which are typically a loss of blood, and with it, blood pressure. More immediate effects can result when a bullet damages parts of the central nervous system, such as the spine or brain. In response to addressing stopping power issues, the Mozambique Drill was developed to maximize the likelihood of a target's quick incapacitation.

A manstopper is any combination of firearm and ammunition that can reliably incapacitate, or "stop", a human target immediately. For example, the .45 ACP pistol round and the .357 Magnum revolver round both have firm reputations 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 (14 g) 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 Convention's 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 game hunters (or their guides) for stopping a suddenly charging creature, like a buffalo or an elephant.