I got a new Shield about 8-9 months ago.  It had three FTE's in about the first 400 rounds. Some were with aluminum Blazer, the last one with HST. These were bad jams - I couldn't just rack the slide to clear them. Couldn't drop the mag either, I had to rip it out. I can tolerate cheap practice ammo jamming, but not HST.

Sent it in to S&W, got it back three weeks later (not bad considering it was over Xmas) with a note saying they polished the chamber and replaced the extractor. Today I finally made it to the range to test it out.  I fired about 300 rounds -  American Eagle, UMC, Blazer, reloads, and about 20 HST.  The gun performed absolutely flawlessly..... until the second to last round.  I squeezed the trigger and "click".... nothing.  I assumed the mag was empty.  But then I noticed the slide was closed in full battery.  I tried to pull the trigger again to make sure it wasn't cocked, it was not.  So I waited about 20 seconds in case it was a squib.   Then I racked the slide and out popped.... an empty case.  

I don't understand this because there was no double feed.  There was an empty case in the chamber, and a fresh round sitting in the top of the mag.   In other words it's as if the round fired but the slide didn't cycle.  The fired round hadn't extracted and a fresh round hadn't been stripped off the mag.  

The only way I know this can happen is if I had mistakenly loaded an empty case into the mag.  It was hot, I was tired, it's not impossible, but I find it hard to believe.   But I guess the fact that the case extracted when I manually cycled the slide proves the extractor was properly hooked under the case rim and working fine.  After I cleared the chamber the last round in the mag fired normally.

Other than this puzzle which I chalk up to user error, the gun functioned 100%.   Based on the frequency of FTE's I had been seeing originally, I think S&W has fixed the problem here.  I think they're aware of some marginal extractors out there.   I strongly recommend that those having such problems take advantage of their great customer service and give them a chance to service your gun.  They pay shipping, and the turn-around time is only 2-3 weeks.

I don't think an empty case is going to feed from the mag and end up in the chamber.

More than likely, it did not extract and the slide did not pick up the next round in the mag, maybe due to a light load or something else.

I hate to piss in your Cheerios but that sounds like a failure to me, but a failure to eject. This was probably caused by an underpowered round and not something with the pistol. From what you're describing it sounds like the slide moved backward enough to reset the trigger but not all the way to fully extract and then eject the casing. I seriously doubt you loaded an empty casing into the magazine and if by chance you did it would be unlikely to feed correctly and would likely have jammed the weapon and not chambered the casing. Did you notice any difference in recoil when the last round was fired?

Glad it sounds like your Shield is fixed.

I'm hoping to get mine back soon after returning it for FTE issues. I emailed them last week and checked on the progress and they told me that it was all set to ship back and that they replaced the trigger bar...... WTF? Hopefully he was looking at the wrong repair ticket.

I'm betting on this. Sounds like the slide moved back enough to reset the trigger but not all the way to eject the round. The casing would have had to have extracted to move the slide rearward so I'm betting it extracted.

Thanks for the feedback everyone.

I know several types of guns will feed empties, at least to some degree, so that didn't sound impossible. But as I said I found it a bit hard to believe I had loaded an empty into the mag.

Your suggestion of a light load makes a lot more sense. This was factory Blazer ammo, not the best ammo on the market, but I guess it can happen with any brand.