Stopping power

Stopping power is the ability of a firearm or other weapon to cause enough ballistic trauma to a target (human or animal) to immediately incapacitate (and thus stop) the target. This contrasts with lethality in that stopping power pertains only to a weapon's ability to incapacitate quickly, regardless of whether death ultimately occurs.

Stopping power is related to the physical properties of the bullet, but the issue is complicated and not easily studied. Although higher caliber has traditionally been widely associated with higher stopping power, the physics involved are multifactorial, with caliber, muzzle velocity, bullet mass, bullet shape, and bullet material all contributing. 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 power is usually caused not by the force of the bullet but by the damaging effects of the bullet, which are typically a loss of blood, and with it, blood pressure. This is why in many instances a single gunshot wound (GSW), with slow blood loss, does not stop the victim immediately. More immediate effects can result when a bullet damages parts of the central nervous system, such as the spine or brain, or when hydrostatic shock occurs. The importance (or lack thereof) of hydrostatic shock and of momentum transfer in determining stopping power has long been controversial among gun users. Some have ascribed great importance to hydrostatic shock; some have tried to entirely discount it; the truth is somewhere in between. Not every GSW produces it.

In response to addressing stopping power issues, the Mozambique Drill was developed to maximize the likelihood of a target's quick incapacitation.

"Manstopper" is an informal term used to refer to 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 "savage foes", 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.

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