Hmm... Sounds like a bad idea to me. There are some small inner workings around the trigger area that are tough to get to. I would think that you would risk it either not drying completely, or worse, having some soap residue build up inside. (I have heard reports of stainless steel rusting, despite the name.) I have the M&P 9. I just use an old toothbrush sprayed with solvent to scrub the frame and chassis.