I owned a very nice drilling by R. Reger, of Konigsburg, in 12, 2 1/2" x 12, 2 1/2" over 8 x 57R/360. I sold it and some others, 2 years ago, in order to generate some "Mad Money" for trophy fees on a hunt to the RSA. It will always be one of those which I greatly regret having parted with. It would put 3 shots under a "loonie", at fifty yards, with the iron sights, and 60+ year-old-eyes, off the bench. It would also put a left/right of "OO" into a 9" x 18" rectangle at 20 yards.
There was an excellent article, by John J. Stransky, in the Handloader Magazine, number 139, May-June 1989, page 22, on the history, dimensions, care, and feeding of this cartridge.
If your drilling does indeed turn out to be so chambered, please keep to MILD loads. These old drillings were not engineered for high pressures. Also, the 360 uses the original .318" bullets, not the later .323". I still see Norma, 196 grainers, at gun shows and recently bought two boxes of 100 at $20.00 each!
The case can be made relatively easilly from 9.3 x 72R brass. Also, both brass, bullets, and loaded rounds, are, or at least were, available from Quality Cartridge, PO Box 445, Hollywood, MD 20636,
http://www.qual-cart.com. 
