A loader for a magazine having an upper open end, a lower closed end, a forward vertical side edge and a rear vertical flat side edge, loader having a vertical channel for receiving therein the rear flat edge of the cartridge, the channel being formed by a pair of flat vertical side members spaced apart in parallel relation and having a rear flat edge where it slidably engages the rear flat edge of the magazine, the magazine being made of ferrous metal and the loader being made of non-ferrous material. A vertically extending tab is mounted in the upper portion of the channel and is provided with a downwardly vertically extending plunger mounted at the lower end of the tab for engaging the edge of an uppermost bullet mounted within the magazine. A pair of outwardly and horizontally extending arms are mounted at the lower ends of the flat vertical sides of the loader, the magazine being adapted to receive a plurality of vertically stacked bullets therein, a spring mounted internally in the magazine for urging the bullets upwardly towards the open end of the magazine and against a retaining means which holds the bullets within the magazine whereby, when the user's fingers engage the arms on the loader and urge the loader downwardly against the action of the spring within the magazine, the uppermost bullet is urged away from the retaining means at the top of the magazine and whereby an additional bullet can be inserted into the magazine above the then uppermost bullet after which the loader can be slid upwardly so that the plunger is completely above the last added bullet to permit the last added bullet to be pushed in by hand against the inner flat edge of the magazine, the loader being maintained in sliding contact within the magazine by virtue of a magnet mounted on the rear of the loader.