section_path: Legal definitions/United States
section_name: United States
paragraph_text: United States
  
  In the United States, under 26 USC § 5845 (a), the term "firearm" means
  
  This is the ATF definition of a title II "NFA firearm", as defined by the National Firearms Act, and not the definition of a title I firearm, which includes firearms not restricted by the NFA. ATF forms dealing with Title II weapons all state the above-mentioned information, however, the above information is only applicable for the purposes of those forms. For practical purposes, a firearm, in the U.S., is defined as the part of a weapon- designed to use expanded gas caused by the combustion of explosive material, to propel a projectile- which houses the fire control group (trigger & sear).
  
  According to the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, if gas pressurization is achieved through mechanical gas compression rather than through chemical propellant combustion, then the device is technically an air gun, not a firearm.