I bought my wife and I 2 40c's a few weeks ago. We have been training with them, as we intend to carry. The day after I read the initial post, I started to experience the same thing. Its a very weird hang up as the slide moves forward after the shot. Feels very jerky in my hand. We have put almost 1000 rounds through both guns, since we are trying to get comfortable with them before we take a self-defense class this Saturday. Put 165 and 180 gr WWB and Remington UMC through them. Also put some 165 Hornaday Critical Defense through them. We have been using full size 40 mags with the x-grip extension piece, and I have felt the hang up with that mag and the 10 round mags. We went shooting last night, and it seemed to be getting worse with mine, and my wife started to notice it too with hers.

I have noticed alot of wear on the bottom of the feed-ramp, where the bullet nose is rubbing. It also seems my slide spring is not as sturdy. I dont know if that makes any sense. I have 4 other M&P's, all full size, and the main springs on them are very stiff and dont move much on the guide rod. Both of our 40c main springs move, and I dont mean compression. It doesnt sound like sending them back in is going to do me much good, but if it does it as badly this weekend during our class, I may go ahead and see if they can find anything.

__________________
M&P 9, 40, 40c, 357, 45, 15T