After a lot of internal debate I broke down and picked up another M&P yesterday. Brought home the M&P Pro CORE 9mm 5". Figure now I have to start the customization all over again. I have a lot of work done to my standard M&P9 I use for USPSA including Apex Competition trigger and full stippling.
Last night I was working on the filling of the engravings and had both guns apart. While staring at the two together had an epiphany. (Maybe) Rather than installing another Apex trigger, more trigger work, more stippling I wondered if I can swap the Pro upper onto my other lower that's had all the work done. So far the only difference I could see is the finger that extends into the ejection port (ejector depressor???) is slightly larger in the Pro model. I did swap the uppers and lower while working on them and did some test racks and seemed fine.
Anyone ever try swapping uppers and lowers and run the guns?

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M&P9, 40, 357, 22, 40 Pro +++