Law enforcement agencies desire to immobilize persons they are pursuing while trying to avoid injury to bystanders. These agencies, and national armed forces, in the process of crowd control during public demonstrations of dissent, also try to employ projectiles designed to incapacitate but not kill. Ammunition used for these purposes is designed to have large dimensions so that impact occurs without penetration to deliver enough kinetic energy for "stopping power".
Such ammunition includes:
lead shot enclosed in a fabric bag ("bean bag")
Plastic bullets or buckshot
Rubber-coated metal buckshot
Injury patterns include lacerations, fractures, and penetrations. Shorter firing distances lead to greater injuries. (Wahl, Schreyer and Yersin, 2006) (Masahiko and Mellen, 2009)
Air guns may include "BB" guns that shoot round projectiles, generally of 0.177 caliber, and may include air rifles that can shoot not only BB projectiles, but also 0.177 caliber pellets of various shapes, including round nose, pointed, wadcutter, or flat, as shown:
The most common shape is the "wasp waist" or "diablo" style.
Though small "BB" pellets may produce injuries. The standard steel "BB" is 0.177 caliber (4.5 mm), and standard velocities may range from 200 to 400 feet per second.
In a study by DiMaio et al, with "wasp waist" pellets of 0.177 caliber, at 290 fps, there was penetration of skin (pellet embedded in skin), and at 331 fps there was perforation through the skin. At 365 fps and higher, perforation always occurred (DiMaio et al, 1982).
The greatest risk for tissue injury with such projectiles is the eye. In a study of "BB" pellets weighing 5 grains fired from a distance of 10 feet at pig eyes determined that a minimum velocity of 246 fps was required to cause corneal perforation with penetration to the retina (Powley et al, 2004).
"Airsoft" ammunition is a slightly bigger plastic or metal versions of a "BB" pellet. The average velocity of air guns firing such projectiles is 366 fps. Such projectiles include 6 mm in diameter plastic pellets that are 0.11 or 0.25 gm, 6 mm metal spheres weighing 0.3 gm, and 8 mm plastic spheres weighing 0.34 gm. In one study of potential eye injury, it was shown that when firing fromn a distance of 2 inches at a pig eye, that penetration of the cornea occurred at 403 fps for the 6 mm pellets weighting 0.11 gm, 325 fps for 0.25 gm 6 mm pellets, and 373 fps for the 8 mm plastic pellets; the 6 mm metal pellets penetrated at 331 fps.
Some law enforcement agencies have adopted "bean bag" projectiles to lessen the potential for injury. Such projectiles consist of a fabric or nylon bag filled with lead shot, and are designed to be nonpenetrating. However, serious injury is possible (Grange et al, 2002).
Plastic bullets, replacing rubber bullets (implicated in three deaths) used as "safe" projectiles for riot control, were shown in one study to be associated with 13 deaths (seven children) by serious head injury, usually when fired at distances less than the 25 yard range considered be "safe" (Metress and Metress, 1987)
Frangible bullets, composed of a metal such as copper powder that is compacted, are designed to fragment on impact, lessening penetration and reducing potential injury to those nearby. The wounding properties are variable. (Komenda et al, 2013)
Exit wounds are uncommon, given the low energy levels of these projectiles. When penetration occurs, the projectiles lodge within tissues. Rare reports of pellet emboli have been reported, and surgical procedures for removal are not without risk for morbidity and mortality (Misseldine and August, 2010).