A ballistics knife has a detachable blade that can be ejected at the push of a button.
The knife in the video below is a spring-powered version with an effective range around 5 yards. The blade travels around 35-40 mph when fired from the push of a button near the weapon’s hilt.
While federal law does not prohibit the possession, manufacture, or sale of spring-loaded ballistic knives, the importation or possessions of these knives in interstate commerce is prohibited. Individual state laws vary throughout the country.
Ballistic knifes using an explosive charge to propel the blade may be restricted by the AOW category of the National Firearms Act.
Check your local laws before purchasing or constructing a blade like the one below.