I too was having an issue with my M&P 40S&W compact (slide locking back and slide failing to lock into battery) so I sent it in to the good people at S&W (although the first guy I talked to told me I was crazy). The gun came back with four items fix/replaced and a clean bill of health. The gun shot well, but I was still having problems with it failing to go into battery. The last two range sessions I have payed real close attention to how and what I'm doing when I shoot.
When shooting if I keep the trigger pulled all the way back, the gun cycles fine. If I slap the trigger and release it completely during recoil the gun will cycle normally. If I ride he trigger to set up a quicker follow up shot, the gun will fail to lock into battery. This will happen 8 out of 10 rounds per magazine.
I know this trigger issue is not normal with M&Ps, I shoot my full size 40S&W and 45acp the same way (riding the trigger, both are/have been 99.99% perfect). Any suggestions where I should look to see if anything is "hanging up".
When shooting if I keep the trigger pulled all the way back, the gun cycles fine. If I slap the trigger and release it completely during recoil the gun will cycle normally. If I ride he trigger to set up a quicker follow up shot, the gun will fail to lock into battery. This will happen 8 out of 10 rounds per magazine.
I know this trigger issue is not normal with M&Ps, I shoot my full size 40S&W and 45acp the same way (riding the trigger, both are/have been 99.99% perfect). Any suggestions where I should look to see if anything is "hanging up".