If you have one of the AR15-22's, you should break it down and check the plastic block that the bolt return spring connects to. Mine and two others have some fine cracks in that plastic buffer block. Usually one in the face/top, one on the underside behind the the metal rail piece and a small one in the groove that the bolt return spring rod sits in. If the one in the groove gets bigger the bolt spring return rod could pop out. S&W says they are not aware of this problem when I called again. I have sent mine back to see what happens. This does not dampen my enthusiasm for the rifle. I think it is great and fun to shoot. I posted this in the wrong forum the other day. S&W 1 800 331 0852 ext 2905#. Just a heads up for you.