I have a 9mm M&P shield that is beginning to experience erratic extraction issues. The gun has about 1200-1800 rounds through it. I loaned it out to a few professional contacts for evaluation, so I don't have a more precise round count. It was one of the Shields that forum member Wayne Dobbs used for his excellent article that appeared in the Summer 2013 issue of Surefire Combat Tactics.
Within the last few hundred rounds I began to notice extraction issues that were not present before. The gun is typically cleaned after shooting, with attention payed to the extractor area in the form of a plastic brush pushing patches soaked in Slip 2000 followed by dry patches. I have not removed the extractor--as that is a bit out of my level.
Below is a photo of one of these situations. In it the case fails to extract and seems to be half in and half out of the chamber. It seems like the extractor lost grip of the case in midst of the sxtraction cycle.
The first instance occurred the second to last time I was shooting the gun with some Ranger Talon 147 grain loads. Since this was the first malfunction I experienced with the gun, I considered it a fluke, and fired another 40-50 rounds of the Ranger Talon ammo without issues.
A few days ago when I took the Shield shooting and experienced the same type of malfunction with the third round out of the gun, which was a round of the same Ranger Talon 147 Grain JHP. At this point I figured that perhaps the Ranger Talon was not a good fit, so I switched to some Black Hills 115 grain Tac-XP +P JHP. I'd fired at least a box of this ammo through the gun in the past with no issues. Well, low and behold, I experienced the same issue with the Black Hills ammo as illustrated in the photo below. For whatever it's worth, this occurred in a different magazine:
The only common denominator between the Black Hills ammo and the Winchester ammo is that they both used Winchester cases.
After having these issues, myself and a friend went on to fire over 200 rounds of mixed ammo through the gun, including brass cased Privi Partisan, Federal, American Eagle, and Estate ammo without any further issues.
I've contacted Smith & Wesson and sent the gun back to be checked. My concern is that it is some type of tolerance stacking issue that they won't find that only manifests itself with certain ammo. To me this would mean that something is indeed wrong with the gun and a potential issue that could show up later with other ammo at an unexpected time.