If you look at the dimensions of the .380 and 9MM there is a difference. There is basically a .020" difference at bottom of the case (forgot names of different areas of a case, sorry) between .380 and 9MM. At case mouth there is a .007" difference. In the groove where half-moon clip is attached, there is around .020" difference, maybe too much. I wouldn't try it. I get my information from the Sierra reloading manual.