Abstract: An improved drum magazine for large caliber ammunition. The drum magazine has a peripheral cover in which a plurality of extracting openings are disposed. An extraction mechanism is adapted to extract via the extraction opening the radially outermost of a plurality of juxtaposed cartridges radially arranged in each ammunition chamber of a plurality of ammunition chambers exchangeably mounted in said drum magazine. The ammunition chambers are independently exchangeably mounted in the drum magazine. Each ammunition chamber defines a storage space for storing a plurality of radially juxtaposed cartridges therein.