Rimfire ammunition is a type of firearm cartridge that ignites its primer through the rim of the casing. The primer is a small amount of explosive material located within the rim area. When the gun is fired, the firing pin strikes the rim, igniting the primer. The hot gases generated by the burning powder ignite the main propellant charge, sending a bullet downrange.
Rimfire ammo is most commonly used in small caliber firearms such as pistols and rifles designed for plinking and target shooting. The low cost and availability of rimfire ammunition make it a popular choice for shooters on a budget. Rimfire cartridges are also popular with varmint hunters who shoot high volumes of rounds to take down pesky critters such as squirrels and rabbits. Rimfire ammo can also be used in shotguns, but the recoil can be excessive for some shooters.