Mike,

I checked the internet and didn't see any 8x57 JR ammo, components or dies. I did see that Buffalo Arms does have 8x57 JRS brass that can be sized down to 8x57 JR brass.

When I bought my BSW (Simson) DR some 5 + years ago, I bought 8x57JR ammo by S&B. I looked and could not find reloading dies for the 8x57JR so just bought regular 8x57 dies and they work well for me.

I bought 0.318"bullets from Buffalo Arms who seemed to be the only company that carried 0.318' bullets. They told me that they swage 0323" bullets to 0.318".

Have you done a chamber cast? I ask because many sporting rifles were chambered for 8x57S even if the barrel was a 0.318" barrel. That allowed the shooter to use either ammo. My BSW is chambered fro the 8x57JRS and the leads taper to 0.318".