A destructive device is a term defined under U.S. federal law, specifically in the National Firearms Act (NFA) and the Gun Control Act (GCA). It generally refers to explosive, incendiary, or poison gas weapons, including bombs, grenades, rockets, missiles, and mines. The term also includes any combination of parts intended for use in converting devices into such weapons, and any type of weapon (other than a shotgun or a shotgun shell) which may be readily converted to expel a projectile by the action of an explosive or other propellant, and that has a bore of more than one-half inch in diameter. Exclusions to this definition include devices that are not designed or redesigned for use as weapons, signaling devices, pyrotechnic devices, surplus ordnance sold in compliance with law, and devices primarily used for non-weapon purposes such as line-throwing or projectiles for propellant-actuated devices. These devices are heavily regulated and possession, manufacture, and distribution are subject to strict legal controls.