Abstract: According to the invention there is provided a mill drum comprising a hollow drum structure in use mounted to rotate about a substantially horizontal axis extending longitudinally through the bore of the drum structure. The drum structure including lifter means mounted thereto to extend into the bore of the drum structure. The lifter means in use when the drum structure rotates and material to be ground has been introduced into the drum structure, selectively catch and scoop up larger parts or fragments of the mill contents from the bottom of the drum structure while allowing smaller particles to remain at the said bottom. The lifter members thereafter drop the scooped up parts or fragments at or towards the upper end of the rotating drum structure causing the parts or fragments to fall onto the rest of the contents at the bottom of the drum structure and thus causing a milling action.