Examples of destructive devices include grenades, grenade launchers, artillery weapons,[1] and firearms (2) any type of weapon by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, the barrel or barrels of which have a bore over one half of an inch (.50 inches or 12.7 mm), excluding some rifles and most shotguns, both semi automatic and manually operated.
While current federal laws allow destructive devices, some states have banned them from transfer to civilians.
In states where banned, only law enforcement officers and military personnel are allowed to possess them.
[3] Muzzle-loading guns are not considered firearms in the US and do not fall under the regulations of the NFA.
For instance, a person may manufacture, possess, and fire a black powder, muzzle-loading cannon of any bore diameter, but may not fire explosive shells from that cannon, as the explosive shell is itself defined as a destructive device.