NJSA 2 C 391 fjersey 2013 title 2 csection 2 c 391 Firearm means any handgun , rifle , shotgun , machine gun , automatic or semiautomatic rifle , or any gun , device or instrument in the nature of a weapon from which may be fired or ejected any solid projectable ball , slug , pellet , missile or bullet , or any gas , vapor or other noxious thing , by means of a cartridge or shell or by the action of an explosive or the igniting of flammable or explosive substances . It shall also include , without limitation , any firearm which is in the nature of an air gun , spring gun or pistol or other weapon of a similar nature in which the propelling force is a spring , elastic band , carbon dioxide , compressed or other gas or vapor , air or compressed air , or is ignited by compressed air , and ejecting a bullet or missile smaller than threeeighths of an inch in diameter , with sufficient force to injure a person .