Abstract: A feeder for a cartridge magazine for a portable firearm includes: a first cartridge supporting surface at an upper region; a second cartridge supporting surface, the first cartridge supporting surface and the second cartridge supporting surface being arranged in a third spatial direction spaced at a distance from one another in such a way that a cartridge for the portable firearm is movable along the feeder in a direction of a front region; a front guide part including a front support surface; and a rear guide part including a rear support surface, a rigid part, and a movable part, the rear support surface including a first support surface and a second support surface, the first support surface being on the rigid part, the second support surface being on the movable part.