I recently acquired a used model 41 in good shape, took it to the range, tried several brands of ammo, functioned OK, decided to give it good cleaning. That is when this problem occurred, it reassembled easily, dropped the slide, dry fired it for function, and when I tried to cock it again it the slide was locked up tight as a drum. What now? I cannot cock the slide for disassembly to see what happened, any ideas? Thanks.