In current usage, a riot gun or less-lethal launcher is a type of firearm used to fire "non-lethal" or "less-lethal" ammunition for the purpose of suppressing riots or apprehending suspects with minimal harm or risk. Less-lethal launchers may be special purpose firearms designed for riot control use, or standard firearms, usually shotguns and grenade launchers, adapted for riot control use with appropriate ammunition. The ammunition is most commonly found in 12 gauge (18.5 mm/.729 inch) shotguns and 37mm (1.46 inch) or 40 mm (1.57 inch) grenade launchers. In the United States, the term riot gun more commonly refers to a riot shotgun. Ammunition Less-lethal launchers can fire various sorts of ammunition, including: Impact projectiles, which rely on kinetic energy, such as baton rounds, bean bag rounds, or rubber bullets Tear gas cartridge Pepper spray Stun rounds Smoke round Less-lethal shotgun shells Less-lethal grenades Sound-emitting projectiles GLIMPS (Grenade-Launched Imaging Modular Projectile System), a round containing a small camera that transmits images To avoid breaking the projectile up, less-lethal cartridges are often propelled by gunpowder, which, when fired, may make an eruption of sparks and smoke larger than those made by modern cartridges propelled by smokeless powder. Chemical agent ammunition Chemical agents may be dispersed in three ways: muzzle dispersion, canister, and ferret. Muzzle dispersion This method is the simplest: the chemical agent is in the form of a loose powder, which is expelled by the propellant of the cartridge. These rounds are used at short range, and have effect from the muzzle to a range of about 30 feet. This method is best used by operators wearing gas masks, as the chemical agent can easily be blown towards the operator. Canister projectiles These are also called gas grenades, and are used at longer ranges. They are analogous to rifle grenades, providing increased accuracy and range over hand-thrown gas grenades. Gas grenades may be used by operators without gas masks, as the agent is only dispersed in the area of impact, as far away as . The agent in gas grenades is dispersed as a gas or an aerosol spray. Ferret rounds These are specialized gas grenades designed to penetrate light barriers, such as windows, hollow core doors, and interior walls, and disperse chemical agents on the far side. Impact rounds Impact rounds come in a variety of shapes, sizes and compositions for varying roles. Impact rounds are made out of materials