Yesterday while shooting my full sized M&P40 (mpj0***) I noticed a vibration following one of the shots. Kind of like a spring breaking or slipping. However, I did not notice any broken springs (the obvious two anyway, trigger and recoil) do not appear damaged to the untrained eye. The gun has about 700 rounds through it. Now during dry firing I get that ringing vibration after the dry fire. Am I paranoid? Is this common? Does anyone know what it might be? I would greatly appreciate any help.