Here is a photo of the chamber cast taken of the chamber in the "System Stahl" Schuetzen rifle that I've discussed here:
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From the measurements it appears to me to be 8.15x52R and not 8.15x46R as I initially thought.

Am I correct?

Using  my Handloader's manual of Cartridge conversion,  the best match I could find was a .32 Winchester Special.  Not an exact match, but came closer on more measurements than any thing else.   

-762x63

                                                                                                                   

I have one in the x52r cartridge,  so does Westerner.  Joe sent me a German  language drawing of the cartridge--In German it's called the Frohn 52/8,15. 
I find the 32 win sp cases are just the right length without trimming other than a light true-up of the case mouth. I use standard x46r dies and the shoulder blows a little farther forward.  In my chamber its not just a long neck x46r. the shoulder is a little longer with less angle. But giving individual craftsmen building them and unstandardized cartridge designs slight variations are to be expected.
 30-30s are too short and would give too much "free-bore" (If I have the term right) unless you design a mold with an ungodly long stop ring. 

To my mind the stop ring should fill the gap between the case mouth and engrave slightly into the leade with a diameter to seal the bore.  Stop-rings that are too short in length or too small in diameter may be one of the reasons that they are out of favor among americans who try to shoot these old rifles in competition.  In the past stop ring molds in the US were very limited in availability as compared the the German catalogues form the bullet swaging houses.  
When I got my 1st center fire euro-schuetzen I only found one--and that was the one from BA---if it worked with your rifles bore and chamber design good---if not, too bad! 
Now with AccurateMolds you can design one specifically for your rifle, or tweak one of the available designs he offers.