A firearm is technically an internal combustion engine. A framework containing levers,springs,cams,and gears, that uses a combustible propellant, ignited by a spark, caused by a human pushing on the accelerator, to consentrate the high pressure gas created by conversion of the propellant, into kinetic energy by pushing a cylinder down a hollow cylinder. Wow. Mysterious Huh. Guess we better be outlawing portable generators and chainsaws too.