Other sorts are designed to be fired from specially-designed pepperball guns whose muzzle velocity is greater than a paintball marker: if the velocity is not high enough the projectile will not break. As with paintball impacts, the capsule's impact is mildly painful and by itself can discourage rioters, but the pepper spray incapacitates and discourages more rioters than the capsule's impact. Types of less-lethal launchers Purpose-built launchers are commonly large bore guns, formerly 25 to 27 mm (0.98 to 1.06 inches), modern versions are 37 to 40 mm (1.46 to 1.57 inches). Dual-purpose guns are usually 12 gauge (18.5 mm/.729 inches) riot shotguns, firing special less-lethal shotgun shells. Single-shot large bore launchers, such as the Milkor 37/38mm and 40mm Stopper, M79 grenade launcher, ARWEN ACE, and RGS-50M, are generally break open designs. The barrels are relatively short, resulting in a carbine sized gun, and may have a shoulder stock and/or a forward handgrip to provide greater control. Pistol launchers exist, but are generally only used for short range, muzzle dispersing chemical agents. Multishot large-bore launchers, such as the ARWEN 37, are usually in the form of a revolver holding five or six rounds in the cylinder. Unlike normal revolvers, the cylinder of a revolving riot gun is too massive to be turned easily by the trigger pull, and is usually turned by a pre-tensioned spring or by a pump action. Shotguns used for riot control are nearly always in 12 gauge, as that is the gauge in which nearly all riot control rounds are made. Generally riot shotguns are used, such as some models of the Remington 870 and Mossberg 500. Due to the reduced power of riot control rounds, there is insufficient energy to cycle the actions of gas operated and recoil operated firearms, so riot shotguns are manually operated, usually pump action. The advantage of using a riot shotgun for riot control is that the shotgun is a dual use firearm, and can switch quickly to and from the riot control role by changing the ammunition. The downside is that it can fire lethal projectiles, and so extra care must be taken in its use to prevent the wrong ammunition from being used. The pepper ball gun, an example of which is the FN 303, is essentially a paintball marker, either purpose built for riot control, or modified from a commercial paintball marker. The pepper ball guns use