Raitor, welcome to the group. I hope that you can solve your problem. Since you are in California, I suppose that your new SD has that horrible bar thing that raises up to indicate a loaded chamber. Ten round magazines right? I bought my SD9 here in Tennessee a few days ago with 10 round mags and they work fine. I bought a couple of extra 16 round mags and I can't get 16 rounds in either one of them. I am not a wimp either, I mean that they will not take 16 rounds period. Not sure what to tell you for advice on your problem. Usually on a "normal" gun the problem of last round not feeding is sometimes related to weak mag springs or something bent or not shaped right on the top of the mag body. However your problem may be related to the new thingy on the slide that indicates a chambered round. If both mags do this all the time, I would call S&W and ask them to send two new mags or springs and followers for yours. What do you think?