Who can "melt in" a red dot optic for M&P 2.0? Floyd's custom is all I've found so far.

I would think Cylinder & Slide would also be able to do that for you, or Mark Hartshorne at Pinnacle High Performance.

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Any trained gunsmith with the proper milling machine should be able to make that happen. Finding someone who's qualified is pretty hard these days. How about BMCM here on the forum, have you contacted him concerning a recommendation? Or perhaps he could do it for you.

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Ret. LE, FA Instr, S&W Armorer