Background: A friend of mine is a passionate WWII arms collector. He recently acquired a Gewehr 43. The gun has been out for a couple of shooting sessions, and was treated gently. Problem Description: On the last shooting outing the bolt locked back in the rear position. There was ammo remaining in the magazine. Normal bolt release procedures are ineffective in the problem resolution. Resolution: No Clue. In that era, I'm a Garand guy. From research though, a leading cause is a binding of the recoil spring. Does this august body have any guidance?