What should I build?

In this chassis, probably long range shooting and hunting. I had a 300 win mag in it so I don't know if the magazines are interchangeable because I was playing with other brass to see if it works in that magazine that came with that stock. I tried 28 Nosler and it wouldn't load and 338 Lapua wouldn't load also the 300 Weatherby, I do reload so it would be cool not have to buy any more dies or bullets. I was even thinking a seven 300 win not sure.
28 Nosler 8.4 twist throated for the 195 EOLs and also load for the 169 Hammer Hunter. Mine also shoots the 180 VLD to .25" 3 shot groups. Covers a lot of bases for me.