I started running ammo out of both magazines today. The short magazine ran just fine every time. The extended magazine ejected after every shot for the fist three rounds. The last four ran without a problem. I showed the gun to one of the guys behind the counter at the range to take a look. He noticed the mag release wiggled front to back as if it were too small for the opening as he did this the mag fell out. I am going to contact S&W about it tomorrow.

Is this a Shield 9mm or 40?

Sorry, shield 40.

There is a thread on this already. Seems to be the norm for the .40 until it's sent back to S&W for a mag catch change.

Magazine or Sheild Issue?

No offense, but I seriously doubt its the norm. My guess is that the problem is on a small percentage of guns and/or users.

My MP40C and some of my PD's MP40 full-size were dropping mags. Ship it back to SW to get it right. Don't try replacing the plastic piece (release button) since it will just waste time. Been there done that. Send to Smith.