I have a 29-2 8 3/8 mid 70's vintage. I am experiencing the classic bolt unlocking and rotating back to previously fired chamber when using full power loads. I sent it back to the factory several years ago for repair. The fix only lasted about 500 full power loads. I am sort of reluctant to return it again. I am told the inertia of recoil momentarily unlocks the bolt and frees up the cylinder. I know in the late 1980's the factory updated their guns with the endurance package which includes a device that positively locks the bolt. Does anyone know if I can buy part(s) to retrofit my gun and would they fit? If not what is the best way to resolve this problem other than using only low recoiling loads. The timing is good and the bolt locks up tight. This is more of a nussiance item than a safety issue. I don't shoot full house loads that often, but when I do I want it to work.