A destructive device is a particular type of firearm or weapon, as defined by the US Internal Revenue Code and is regulated by the National Firearms Act (NFA) of 1934. This type of device is typically controlled, though not necessarily illegal, in the US and certain taxes and licenses must be obtained to own or operate such a device. The classification of these devices was established in an effort to regulate the distribution and use of certain weapons following the end of Prohibition in the US. A destructive device is typically defined as either an explosive device or a firearm with a barrel bore width greater than 1/2 inch (1.27 centimeters).
The NFA was established in an attempt to diminish the use of highly destructive weapons by criminals, especially those involved in illegal alcohol production and distribution during Prohibition. An initial effort was made to outlaw the ownership and use of all firearms, but this was abandoned due to the Second Amendment to the US Constitution. The law that was passed, however, identified and limited the use and ownership of a destructive device.
As established in the US Code Title 26, Subtitle E, Chapter 53, Subchapter B, Part I, Section 5845, the definition of a destructive device is anything that falls into one of three categories. It is “any explosive, incendiary, or poison gas” in the form of a “bomb, grenade, rocket having a propellant charge of more than four ounces, missile having an explosive or incendiary charge of more than one-quarter ounce, mine, or similar device.” A destructive device is also a firearm of any kind, regardless of name, “the barrel or barrels of which have a bore of more than one-half inch in diameter;” though exceptions are made for some shotguns that are “recognized as particularly suitable for sporting purposes.”
The US Code also indicates that “any combination of parts either designed or intended for use in converting any device into a destructive device” as defined in the other two categories are also destructive devices. Any firearms or devices that have been modified to serve purposes other than as weapons, such as firearms with a wide bore that have been altered for use as safety equipment, can be excluded from these definitions. Antiques and devices that are approved under special circumstances are also typically excluded from these restrictions. Possession or sale of a destructive device is typically taxed and regulated in the US, though some states have outlawed private possession of such devices, so care should be taken by anyone transporting such devices between states in the US.