.22 CB Cap (Conical Ball Cap) is a variety of .22 caliber rimfire ammunition which has a very small propellant charge (usually no gunpowder, just the primer), resulting in a low muzzle velocity of between 350 and 700 ft/s (110 to 210 m/s). This is similar to the muzzle velocity produced by a low to mid-power .22 pellet gun, however it should be noted that the bullet from a .22 CB cartridge is significantly heavier than a typical airgun pellet and therefore carries more energy. Due to their low power, CB rounds can be trapped by most pellet gun traps. In longer rifle barrels the CB has a seemingly non-existent, very quiet report due to the lack of residual pressure at the muzzle (see Internal ballistics).
The original .22 CB cartridge has the same case as the .22 BB, but there are now low-power .22 rounds sold as .22 CB Short and .22 CB Long which come in the more common .22 rimfire cartridge cases. The longer cases will allow the rounds to be fired in magazine fed firearms, in which the tiny CB Cap cases would jam. So while having the same length, the modern .22 CB Short and the .22 Short are two different cartridges. The CB has a reduced powder load and is kept (as mentioned above) between 350 and 700 ft/s, while the Short with an increased powder amount launches the same 29gr bullet around and above 1000 ft/s.