Stopping power
Stopping power contrasts with lethality in that it pertains only to a weapon's ability to make the target cease action, regardless of whether or not death ultimately occurs.
Stopping power is related to the physical properties and terminal behavior of the projectile (bullet, shot, or slug), the biology of the target, and the wound location, but the issue is complicated and not easily studied.
This led to the introduction or reintroduction of larger caliber weapons (such as the older .45 Colt and the newly developed .45 ACP) capable of stopping opponents with a single round.
During the Seymour Expedition in China, at one of the battles at Langfang, Chinese Boxers, armed with swords and spears, conducted a massed infantry charge against the forces of the Eight-Nation Alliance, who were equipped with rifles.
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.
Some bullets are constructed by bonding the lead core to the jacket to promote higher weight retention upon impact, causing a larger and deeper wound channel.
Bullets that might be considered to have stopping power for dangerous large game animals are usually 11.63 mm (.458 caliber) and larger, including 12-gauge shotgun slugs.
These bullets are expected to impact and penetrate, and transfer energy to the surrounding tissues and vital organs through the entire length of a game animal's body if need be.
The stopping power of firearms when used against humans is a more complex subject, in part because many persons voluntarily cease hostile actions when shot; they either flee, surrender, or fall immediately.
Fragmenting rounds have been shown to be unlikely to obtain deep penetration necessary to disrupt vital organs located at the back of a hostile human.
By contrast, a hole through an arm or leg which hits only muscle will cause a great deal of pain but is unlikely to be fatal, unless one of the large blood vessels (femoral or brachial arteries, for example) is also severed in the process.
In this case, the resulting blunt trauma can slam the vertebrae together hard enough to either sever the spinal cord, or damage it enough to knock out, stun, or paralyze the target.
While the bullet did not directly contact the spine, and the wound incurred was not ultimately fatal, the temporary cavitation was sufficient to render SA McNeill paralyzed for several hours.
The tensile strength of muscle ranges roughly from 1 to 4 MPa (145 to 580 lbf/in2), and minimal damage will result if the pressure exerted by the temporary cavitation is below this.
At typical handgun velocities, bullets will create temporary cavities with much less than 1 MPa of pressure, and thus are incapable of causing damage to elastic tissues that they do not directly contact.
Whether a person or animal will be incapacitated (i.e. "stopped") when shot, depends on a large number of factors, including physical, physiological, and psychological effects.
The only way to immediately incapacitate a person or animal is to damage or disrupt their central nervous system (CNS) to the point of paralysis, unconsciousness, or death.
Several scientific papers reveal ballistic pressure wave effects on wounding and incapacitation, including central nervous system injuries from hits to the thorax and extremities.
[16] These scientists observed neural damage in the brain caused by the distant effects of the ballistic pressure wave originating in the thigh.
Animals will not faint or surrender if injured, though they may become frightened by the loud noise and pain of being shot, so psychological mechanisms are generally less effective against non-humans.
According to Dr. Martin Fackler and the International Wound Ballistics Association (IWBA), between 12.5 and 14 inches (320 and 360 mm) of penetration in calibrated tissue simulant is optimal performance for a bullet which is meant to be used defensively, against a human adversary.
The IWBA's and FBI's penetration guidelines are to ensure that the bullet can reach a vital structure from most angles, while retaining enough velocity to generate a large diameter hole through tissue.
Excessive penetration or overpenetration occurs when a bullet passes through its intended target and out of the other side, with enough residual kinetic energy to continue flying as a stray projectile and risk causing unintended collateral damage to objects or persons beyond.
It postulates that the pressure wave exerted on soft tissues by the bullet's temporary cavity hits the nervous system with a jolt of shock and pain and thereby forces incapacitation.
Proponents of this theory contend that the incapacitation effect is similar to that seen in non-concussive blunt-force trauma events, such as a knock-out punch to the body, a football player "shaken up" as result of a hard tackle, or a hitter being struck by a fastball.
The myth of "knockback" has been spread through its confusion with the phrase "stopping power" as well as by many films, which show bodies flying backward after being shot.
The ability of a bullet to "knock down" a metal or otherwise inanimate target falls under the category of momentum, as explained above, and has little correlation with stopping power.
This hypothesis, promoted by Evan P. Marshall, is based on statistical analysis of actual shooting incidents from various reporting sources (typically police agencies).
[citation needed] Others 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.
