The sheet metal screw in the side of a disk does work for small charges below 3.5gr. It has been my experience that the Lee charge bar isn't dependable below 4.0gr. Since the Lee micro disk is no longer produced, I followed an old reloaders advice to replicate the discontinued micro disk. Buy any Lee powder disc, tape the hole closed on one side, fill the holes with two part epoxy, let dry thoroughly. Remove the tape, drill a small centered 1/8th inch hole in the epoxy, slowly increasing bit size or wallowing out while testing to achieve your desired low drop charge value. Then measure the value and etch the value on the disc hole, awl, dremel, whatever you have available. Repeat for the other 5 holes for each desired different diameter/charge.