My M&P FS 9mm from 2012 is still having accuracy issues after two trips back to the factory. First time they adjusted the rear sight to shoot far off from where it was suppose to be
and the second time they replaced the barrel. After the barrel replacement and a 20lb recoil spring, it's a little better but nothing I'd call good.
BTW, I've shot 3 different weights of ammo, in +P and standard pressure, in seven different brands and the point of impact is sporadic at 15 yards. According to the S&W techs I've talked to, they're supposed to get no more than 3" and 25 yards. Bench rested or off hand had mine getting 10" at 15 yards and now it's probably down to 7-8" at best at 15 yards, however one shot will be about 5-6" from the one before it during slow fire and careful aiming.
I've tried all 3 backstraps and have an Apex hard sear and my DIY polish job on the striker block. I've had people tell me and many others constantly that it's not the gun it's the shooter and the M&P is some magical machine that takes many rounds to get accustomed to which is total BS unless you're a beginner and have only shot a handful of rounds through the M&P. I personally only take no more than a box of ammo to get right on consistently with any new platform and after over 1,000 rounds now, it's still the same as my first range trip. Just throwing that out there since you'll more than likely run across some of the same comments. In any case, I shoot my 2 finger grip, shorter sight radius Shield better with a 2" group at the same 15 yard distance using the same ammo I've tried in the FS model.