Illinois Statutes Chapter 430. Public Safety § 65/1.1. Definitions said:
“Firearm” means any device, by whatever name known, which is designed to expel a projectile or projectiles by the action of an explosion, expansion of gas or escape of gas; excluding, however:
(1) any pneumatic gun, spring gun, paint ball gun, or B-B gun which expels a single globular projectile not exceeding .18 inch in diameter or which has a maximum muzzle velocity of less than 700 feet per second;
(1.1) any pneumatic gun, spring gun, paint ball gun, or B-B gun which expels breakable paint balls containing washable marking colors;
(2) any device used exclusively for signalling or safety and required or recommended by the United States Coast Guard or the Interstate Commerce Commission;
(3) any device used exclusively for the firing of stud cartridges, explosive rivets or similar industrial ammunition; and
(4) an antique firearm (other than a machine-gun) which, although designed as a weapon, the Department of State Police finds by reason of the date of its manufacture, value, design, and other characteristics is primarily a collector's item and is not likely to be used as a weapon.