Handgun effectiveness is a measure of the stopping power of a handgun: its ability to incapacitate a hostile target as quickly and efficiently as possible. Overview Most handgun projectiles have significantly lower energy than centerfire rifles and shotguns. What they lack in power, they make up for in being small and lightweight, lending to concealability and practicality. Handgun power and the effectiveness of different cartridges are widely debated topics. Experimental research among civilians, law enforcement agencies, militaries, and ammunition companies is constantly ongoing. Factors that can influence handgun effectiveness include handgun design, bullet type, and bullet capabilities (e.g. wound mechanisms, penetration, velocity, and weight). Factors Cavitation Most handgun projectiles wound primarily through the size of the hole they produce, known as a permanent cavity or simply a bullet hole. Rifles are capable of much higher velocities with similar cartridges and add Temporary cavitation for additional lethality. Many handgun bullets move too slowly to cause temporary cavitation, but it may occur if the bullet fragments, strikes inelastic tissue (liver, spleen, kidneys, CNS), or transfers at least of energy into the subject. This last instance usually requires a larger and/or higher velocity projectile than is commonly used with handguns. Penetration One factor used to measure a handgun's effectiveness is penetration. The FBI's requirement for all service rounds is penetration in calibrated ballistic gelatin. This generally ensures a bullet will reach the vital human organs from many angles and through many different layers and materials of clothing. Penetration is often argued as the most important factor in handgun cartridge wounding potential outside the skill of the shooter. Ballistic Pressure Wave/Hydrostatic Shock There is a significant body of evidence that Hydrostatic shock (more precisely known as the ballistic pressure wave) can contribute to handgun bullet effectiveness. Recent work published by scientists M Courtney and A Courtney provides compelling support for the role of a ballistic pressure wave in incapacitation and injury. This work builds upon the earlier works of Suneson et al. where the researchers implanted high-speed pressure transducers into the brain of pigs and demonstrated that a significant pressure wave reaches the brain of pigs shot in the thigh. These scientists observed neural damage in the brain caused by the distant effects of the ballistic pressure wave originating in the thigh. The results of Suneson et al. were confirmed and expanded upon by a later experiment in dogs which "confirmed that distant effect