The present invention relates to systems and methods for reliably limiting the cartridge loading capacity of firearm magazines. In one embodiment, a magazine capacity limiting assembly includes a limiter body and a limiter base. The magazine capacity limiter body reliably operates with a cartridge follower of a firearm magazine. The limiter body is installed substantially within coils of the magazine's spring, thereby limiting the travel of the follower within the magazine body to limit the magazine's cartridge capacity. The lower portion of the limiter body can include a plurality of extensions is configured to be severed at a corresponding plurality of pre-determined locations corresponding to a plurality of cartridge capacities. The limiter may also include a cupped top configured to be securely coupled the cartridge follower of a corresponding type of firearm.