Matt's results with a m46 in 9.3x57 mirror mine. .370" grooved diameter and .357" being the largest that will fit comfortably. I also used necked up 8x57, but first necked them straight, then necked down for a crush fit. My rifle had .019" headspace - too much for a simple necking up and fire forming operation. In the interest of case longevity, I had to form a false shoulder and the only way to do that was to neck them larger, first. If I wanted to shoot cast bullets, I'd have to open the chamber neck to allow larger bullets.

Now - the M146's usually have, I'm informed, .365" to .366" groove diameters. If you want to shoot cast bullets, do indeed, slug the bore to find out what you're is anduse appropriate bullets. If you have a .370" groove diameter, cast bullets are not an option unless you open us the throat.

Nice rifle, btw- GREAT find.

Loads - factory is about useless - for me.

Hornady makes the dies & I like mine.
In my M96, I run 225gr. at 2,550fps, 232gr. at 2,450fps, 270's at 2,300fps, 286gr. at 2,200fps, 293gr. at 2,200fps and 300gr. at 2,175fps.

My 300gr. bullets are 125fps faster than the factory 286gr. Normas.

In my rifle, all bullet weights shot into the same group will make a 2 1/2" group, shot off bags at 100meters.
Individual groups run 3/4" to 1 1/2".

Your model 98 can easily add 100fps - probably more to those figures.

The 9.3x57 is a wonderful round, easy to shoot and very effective on moose - mine was 200yards and shot with the rifle's iron sights. I had filed out the rear sight into a wide V as the U notch was too tight and I like the wide V.

Since it was already drilled and tapped, after that first year, I mounted a 3-9X M3200 Bushnel on it, hence the good shooting.

Lee can make you dies to reduce .375's to .366" or .367". A reduction die is how I was able to test 225gr., 270gr.(other than Speer) and 300gr. bullets.

That 300gr. load matches or exceeds the load used in factory .333Jefery, seems to me. Remember the picture of the lion charge in Taylor's book? The lion took a .333 in the face? haven't read that book for 30years, but I can still picture that photo - as vividly now as when it was in front of me.