So u are telling me that ur gun smith told you the Shield has both an extractor and an ejector? And ur also telling me he is a certified S&W gunsmith.........I'd like to know where he printed up his certificate. Because the last i check ANY m&p only has an "ejector", no such thing as an extractor. They are sometimes referenced as the same but there is only ONE part number and ONE part.
Oh and for giggles, u can tell him that the 9mm and .40 have the same exact ejector part numbers. I wonder how he will explain to us that they are different.
I'm sure glad u trust this guy. But my advise would be to find a new gunsmith.