A high-capacity magazine that is cylindrical in shape and resembles a drum is known as an airsoft drum mag. These magazines are used in airsoft guns. This particular kind of magazine winds the bb rounds up into a spiral around the middle of the magazine. There are some drum magazines that can hold up to three thousand rounds. Sometimes they are powered by a battery and activated by the sound of your gun, and other times they will wind up the magazine when you press a button. Drum magazines are available for airsoft rifles and pistols, and are compatible with all of the most popular models, including the M4, G26, AK47, and MP5, among others.