A rotary ammunition magazine for a rifle has a follower that is spring biased and rotates about an axis to move cartridges for feeding to the rifle's chamber. The follower has a rib and/or a projection on a surface facing the cartridges. The rib engages the last cartridge in a stack and directs the force from the follower in the direction of movement of the cartridges within the magazine. The projection engages the extractor groove in the last cartridge to prevent it from moving under inertial forces caused by recoil. The rib engages and prevents the last cartridge from moving down the follower. The projection and rib prevent bolt override malfunctions.