I have 2 fairly new M617's, 4" & 6", You might remove the side plate, 3 screws, put the screws back in the same spots, spray it out with Rem oil, or lots of brands like that, clean & lube type spray, put a drop of Lucus Gun Oil on all moving parts, then run 1000-1500 rounds thru it.. If you want it a little lighter trigger pull, I replaced the rebound spring with a 15 lb. one, Mine when New was 12 1/2 lb., Now they have around 9 lb., Double Action.. 3 1/2 Single Action, But that's where I want mine, No Mis-Fires, my 6" was pretty clean, the 4" was black & nasty inside for some reason. Don't forget to clean under the ejector star after each range session. That was just Me. good luck..