I just bought a 40c a month ago and am experiencing the same thing. Mine is currently back at S&W being looked at. I noticed it right away. The slide has a herky-jerky feel to it. Feels like something interferes with the slide travel and somehow the momentum is messed up. It is hard to put into words, but it just doesn't feel right...sort of an unsettling feeling like it might not make it back into battery. Mine hasn't failed yet, but I thought I should send in to be looked at. I have owned a number of automatics in 9mm and 45 Acp, but this is my first .40 cal. I have never experienced this effect with any other gun. I hope it isn't a "40 thing". I amreally at a loss for what is causing this.

I have a feeling that I will get it back with a note that says everything is in spec and that there is nothing wrong. It is tough to describe the problem, so I bet it will be hard to diagnose.