That 44 is very unusual!! compared to the common 41.. (got several 41's. working)
The bits lock in by turning the end knurl, not by pulling it back.. the end cap unlocks by pulling the small screw down, then rotate the cap, 7 settings, the light setting is ideal for small bits, not too much pressure driving the bit, so it "drills" holes without damage to hole.. the drive gear & spring is heavy duty & easily accessible, just loosen middle knurl nut & pull apart... Just LOVE it.. my 1st.