WBLDon,
Where was the rifle proofed? In Germany it would be marked as to bore(not groove or bullet) diameter and a 30 cal. would usually be 7.6.
In Austria, it would usually be marked as to groove or bullet diameter and 7.2 is .283"( 7.3 is .287"). I suggest you try a 7x64 Brenneke round. This is a world famous and very popular caliber in Europe.
Mike