Ray Gregg aka Bearcreek Guns in Seleah, WA works on them.
If you remove the magazine on a 742 and hold the bolt open, you can inspect the grooved rail for wear. That is the weak link because the rotating bolt is too hard vs the frame.
I have owned three.. 308, and two 30:06 that were all accurate, say 2.5" at 100 yards.
Shops do sell them used, but a 6mm is something I have never come across. Just don't use it as a monthy target shooter.