Have a look into Jon Speed's "Mauser - Original Oberndorf Sporting Rifles", pages 96 -99, 115, 434. The first K action he recorded is dated 1900. The K actions were first made for Mauser's own short cartridges 6.5x54 and 8x51. The .250-3000 Savage came much later, made for export to the USA. But large ring K actions are indeed super rare.