My preferred medium calibre is the 9.3x74 which is so versatile)you can use it on game up to Elephants). However if you want lighter, then 8x57 or 7x65 would be good options. RWS makes a great range of Ammunition for the 7x65 but I'm not sure about the 8mm.
Being that the 8x57R is used extensively on driven hunts in Europe where reloading is not popular, there must be a few factory offerings in this calibre.