[Thor]

The Sear spring might be too weak too and the disconnector would be my guess. Usually this is a function of the trigger lever. Does the Luger have a white streak on the receiver just left of the sideplate. This is usually caused by the trigger lever being held too deep toward the disconnector (and against the reciever) during the firing sequence. When you pull the toggle back slightly does the sear spring click the safety bar into the gun, is so the sear spring is too weak and the gun is closing before the firing pin is caught and held.