Abstract: The invention relation to a device for identifying and checking ammunition on an automatic-loading device of a firearm. The firearm is capable of firing ammunition of different types. The device includes a rotating magazine having adjacent chambers for accommodating an ammunition round. The device further includes at least one fixed code reader arranged on a path of the magazine. The code reader includes optical detectors aligned in parallel with a center line of the ammunition round. Each ammunition round has a cylindrical coding zone on a cartridge thereof. The coding zones consist of annular coding tracks. The device utilizes the coding zones to identify and check the location of ammunition to expedite loading of the firearm. A method of utilizing the device is also provided.