A drum magazine is an enlarged magazine with high capacity. Usually these have the shape of a drum, or a double drum. In the airsoft sector these magazines are often electronically reloaded and have a very high capacity. BB capacities of over 2,500 shots are possible.
Most drum magazines can of course be found for AEG’s and there for M4/AR15 or G36 variants. AW Custom now also offers a drum magazine for GBB rifles and several for GBB pistols.
An exception are belt drums for machine guns. These are often shaped like a drum, but not like a magazine. From a technical point of view, only the belt itself is important for this type of weapon. The drum is only used for safe transport. The machine gun would also only work with the belt. Of course, this does not apply to airsoft weapons, so here is also a picture of a belt drum.