8x56r, 303, 30-40 do not have an extractor groove. This might be 8mm Mauser. German or Yugo? Not sure.
https://forums.gunboards.com/showthread.php?869593-What-rifle-uses-8x57-JR
https://www.icollector.com/8X57-JR-JRS-AMMO_i31510462
https://www.icollector.com/RWS-8X57-JR-AMMO_i31511119
8x57JR?
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=547988&page=all