I've done the trigger on a good dozen MA Compliant M&P's of various calibers and models. (They are pretty much similar internally.)
Personally, I find that just a $40 Apex sear added to the factory springs will usually result in a pull in the 5.75# range (+/-). It will also feel crisper.
It's all I do for my personal M&P.s There are plenty of Utube video's on how to change out the sear and no special tools are required other than a punch (which can be made from a nail in a pinch)


If you want improved reset, flat faced triggers, etc, then get ready to pay for it though. That's the version most shops push.

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Dave