My experiences when using x57 brass, both S&B 8x57IS and Norma 9.3x57, are unsatisfactory. Of course I first thought that I could open them up to take .375 bullets and go bang. It ain't so, as I got a lot of misfires due to excessive headspace. As I wrote before, the 9.5x57 M-Sch is not merely an opened up standard x57 case, but a somewhat improved case. The base diameter is the same, but other critical dimensions differ considerably. According to the current CIP tables the 9.3x57 has a max body length to shoulder of 45.86 mm = 1.806", the 9.5x57 M-Sch 46.5 mm = 1.831", 0.64 mm = .025" difference. This is not all because the shoulder diameters differ too, 10.95 mm = .431" for the 9.3 and 11.9 = .469" for the 9.5, another difference of 0.95 mm = .038". These differences sum up to an excessive headspace of about one full mm if you try to use opened up 8x57 or 9x57 cases "as is". So, if you insist on using standard 8x57 or 9.3x57 cases, you have to first open up the necks to about 10mm = .400", then to size them down again to form an auxiliary shoulder for fireforming. You will most likely have to anneal the cases in the proceedings. I make my cases from once fired W-W or S&B .30-06 brass, as these brands don't require neck reaming. Anneal,trim to 56mm, open up the necks to 9.5mm (two steps), resize in a 9.5x57 M-Sch full length die. Both ways need more work than simple resizing, so take your choice. Here is a photo of a 9x57 cartridge on new Norma 9.3x57 brass above a 9.5x57 M-Sch on reworked W-W 30-06 brass.

BTW, the CIP max pressure of the 9.3x57 is 2600 bar against 3050 bar of the 9.5x57 M-Sch.