Thanks for this thread. I've got three juniors shooting M&Ps our oldest one needs a trigger job. I called Apex and left a message. They called back a couple of days later and I've got what I need on the way.
If you've got a bad trigger on one, it might be beyond the Apex sear to correct. S&W has excellent customer service. If the pistol is exhibiting unusual function, you might want to call them before you do the Apex install to rule out other issues. They take care of shipping under their warranty.