Just measured an old M21 barrel in 8x57:

Diameter at the muzzle ( the last 55 mm / front sight ramp removed ) : 13,4 mm

Rifling depth of the 9,3 x62 : 9,28 mm the remaining 4,12 mm divided by 2 : 2,06 mm(0.0915 inch)

That is what a shotgun shows at the muzzle.

Muzzle pressure of the 9,3 x62 runs easy to 500 bar ( 7.553 psi )

I presume your barrel has the same dimensions .

I would not be lucky knowing these facts.

Anyway, if you trust your riflemaker , let him start his work.