A firearm is generally a rifle, pistol, shotgun, or other portable weapon that expels a projectile (bullet) by use of an explosive action. The definition of a firearm may vary from state to state under state statutes—and under federal statutes—and related items such as a muffler or silencer may be included in the definition of a firearm for purposes of certain criminal offenses (crimes).
In Wisconsin, a firearm is defined under state law as any weapon that can expel a projectile by the action of an explosive or any device that is designed or has the potential to be converted into such a weapon. This includes rifles, pistols, and shotguns. Wisconsin statutes align with federal law, which also defines a firearm in a similar manner under the Gun Control Act of 1968 and the National Firearms Act. Additionally, under both Wisconsin law and federal law, items such as mufflers and silencers are considered firearms when they are part of or attached to the weapon. These definitions are important as they determine the applicability of various firearm regulations and criminal statutes, including those related to possession, transfer, and use of firearms and related accessories.