A bag loader apparatus for filling an elongated bag may comprise a base assembly, and a bag interface assembly for removably mounting a bag thereon and forming a tunnel with a rear opening for fluid communication with the bag. A primary auger assembly has an output opening in communication with the tunnel of the bag interface assembly. In some embodiments, a bag mounting assembly may be configured to lift a bag onto the bag loader apparatus into a position for loading the bag by the apparatus. In some embodiments, a plurality of bag securing elements on the bag interface assembly may be configured to secure a portion of the bag to the bag interface assembly. In some embodiments, an auxiliary auger assembly carried on the base assembly may be configured to feed material into the primary auger assembly.