I regularly clean my mp40 and enjoy a complete disassembly. I can not get past the removal of the take down lever pin. The rotating pin that you rotate down 90 degrees to field strip the firearm. It won't come out. I have watched many videos of the disassembly and everyone seems to be able to remove it fully without any problems. It is held in pace by a small spring. I have to remove the drop lever pin in order to take a part and clean the trigger assembly.