I've been told that the 146's had closer tolerances than the M46's.
I would not let the M46's 'loose' tolerances prevent me from buying a 146.

9.3x57, a member here has or had one of the 146's which had a .365" or .366" groove diameter, which is perfect.

Mine would have been OK for cast bullets if I had opened up the neck of the chamber neck as has been done by others - someone here did just this and I cannot remember who that was - for that I apologize. He has had good results with cast in his rifle.

There are a number of moulds available as well as commerically cast bullets for this calibre.

If the bore is oversize, Lee sells dies for re-sizing lubed bullets, or even for reducing .375" down to .366" with jacketed bullets.

It is a hell of a good round. Even though I was shooting bullets up to .005" undersize, 2 1/2 thou per side, my rifle put them all into smaller than 1 1/2" at 100 meters off bags with the scope.

Using the 293gr. TUG's and 45gr. H4895, I usually got cloverleafs. They were only running 2,100fps, however the 300gr. sized down Hornady's were making 2,175fps with the same load - THAT is the same velocity as the original 9.3x62's factory 286gr. softs and solids.