encore rear sight holes very deep????

[northern hunter]

 :'(Hey guys,my gunsmith just informed me that  he cant rechamber my 358 win barrel to 350 Rem Mag.because the rear sight or scope base holes are to deep....They are .210 deep,the chamber wall thickness is not thick enough after opening up the chamber to 350 rem,for safety reasons he wont do a job unless there's at least 50 thousands of metal left under the screw holes.Anyone ever have this problem before?The scope base screws only go down about half way so why would anyone drill them so far?This is on a TC custom shop blued barrel .
Anyone ever measure there screw hole depths?

[southernutah]

I bought a new factory barrel years ago  in 308 Winchester  and wanted Virgin Vally to rechamber to 300 WSM. they checked the scope base holes first as they had some come in that were to deep to rechamber.