If it were me, the only reason I'd care to know deeply as to what happened to the barrel would be for purposes of litigation.
If I wanted to litigate, I would not go to a metalurgist or any other seemingly qualified person because a good defense attorney will disqualify them if they are clever enough.
Tell your friend to lookup up the London Proof House. (worshipful company of gun makers...I think that's the full name) They do post mortems on failed guns and their opinion would be irrefutable by comparison to an American metalurgy expert.
The unfortunate thing about Turkish guns is that their proof laws carry no real weight. They are not a CIP recognized country. (CIP is the international proof standards consortium by which most of Europe abides)
