Back in July I bought a Pro Series Compact and have been having continuous issues with it. First trip back to the factory fixed the failures to return to battery and the brass hitting me in the forehead and reduced the number of failures to extract but didn't eliminate them (they tweaked the barrel to slide fit, the ejector, and the extractor). Second trip back to the factory they replaced the extractor and spring, but I'm still having failures to extract.
Here's the part that baffles me; the gun consistently has failures to extract between rounds 30 and 40, but otherwise works fine. The spent casing remains in the chamber and the gun attempts to feed the next cartridge from the mag, just so I'm clear about the nature of the malfunction.
Knowing that there was a consistent problem at that point (with different magazines and ammo), I assumed that I was loosening my grip or fatiguing and causing the malfunctions, so the last couple of trips out I took a break before reaching the magic number and paid extra close attention to my grip and shooting form when I resumed shooting. Two trips ago it failed to extract at round 32, last time I had two failures to extract at rounds 34 and 39 (with two different mags).

I'm fairly certain that I'm not the problem, and I have tried deliberately "limp-wristing" the gun for a few mags in the past and it functioned fine.
I'm sure the ammo is not the problem because it has happened with four different brands of factory ammo (Remington, Winchester, Speer, and PMC), both FMJ and premium ammo (Golden Saber and Speer Gold Dots) and the timing on the malfunction is too predictable to be caused by random out of spec rounds (plus with all the ammo I have run through this gun that would be an unacceptably high number of bad rounds).
I'm pretty sure its not the mags because it has happened with whatever mag happens to be in the gun between rounds 30-40, including the stock mags, Mec-Gar, Colt, and brand new Wilson mags.

In short, I'm stumped and would appreciate any thoughts on what the problem might be.

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Just a wild guess. Perhaps an issue with a rough or undersized chamber heating up during firing.

That's what I was starting to think since the gun does get shot for several mags before the problems start.

Thanks for the input, I will see if I can have a local smith check it for me. I'm just surprised that S&W didn't check this on one of the gun's two trips back to the factory...

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