Wild rose makes a good point.
However in my own experience with my 300 wsm
I bought a box of factory rounds. And conditioned the barrel with them then called it good, I had talked to my Gunsmith about free floating the barrel (I has the rem sps stock that can't be floated) and he told me to wait and see how it shoots before I worry about it, it was shooting 3/4 inch groups and I was happy with it but I still got a new stock and floated the barrel afterwards.
As for your load it all depends what distances you'll want to be shooting. I just posted a thread called "210's and 300 wsm" I got great luck with the 210 bergers.
Good luck with the loads and welcome to the site