I would totally disagree with your 3rd fromn last Para Buccaneer, starting 'There is the more.......' What you have stated is factually wrong. We used to fit (as in stone, adjust and correctly fit) new and even used bolts to rifles every day. To say that it could be unsafe is............., er.......... Anyway
And That's the UKMilitary. What about a US gunsmith doing it in the USA
or Australia
or NZ where they don't do proofing as such..........?