Abstract: Method and apparatus for loading cartridges into a relatively large capacity firearm magazine of, for example, the rotating drum type is disclosed and includes structure defining a plurality of generally parallel extending slots for receiving cartridges in a horizontal attitude and arranged as a plurality of generally parallel, vertical columns of superposed cartridges lying in the slots. The structure also includes a sliding panel with a single cartridge-passing opening therein, which opening may be selectively aligned with any one of the cartridge columns. The cartridge-passing opening is then aligned with a magazine loading port and the cartridges transferred one at a time from the bottom of a column into the magazine. When a column is exhausted, the structure is shifted so as to align a different column with the aperture and loading port whereupon that column is transferred one at a time to the magazine.