Check out APEX Tactical, they make a couple of drop-in triggers kits for M&Ps. The Comp AEK is suppossed to produce a sub-3# trigger, but is only recommended for competition use. I've tried the Duty/Carry AEK, its right around 4.# or so and really smooth. Just a heads up though, both of those kits seem to put the trigger break a bit further back in the pull. Pretty much minimizes over travel, but actually increases all the take-up/pretravel. Don't know if that's an issue for you. You might want to see if they've come out with the FSS for the .45, its supposed to mimic a 1911 trigger. If APEX is back-ordered, check out Speed Shooters Specialties, they carry most of the APEX stuff and pretty specialize in M&P add-ons.