Mike,
I think you could use normal 8x57 JS Mauser dies, with a different shell holder of course.
Are the drillings as expected? Good bores? My "cheap" Krieghoff 8x57 IRS came here recently and while the rifle bore is not pristine (somewhat tired from the chamber up, but sharp and deep towards the muzzle) the first test shooting was satisfactory.

With kind regards,
Jani