kc...

Slug the bore. Many of the 8X57JRs have a .320, and you can use .321 170gr 32 Spl bullets. It was what we did many years ago, when there was no US source for .318 diameter bullets.

Many of the pre-war 8mm drillings have a loose bore, and 5 out of the 7 I've owned in 8X57 had .320 or .321 bores, although designated for the .318.