Welcome to the forum. Glad to have you here. That's a pretty good first post.
You've built yourself a nice rifle although the it seems the bolt will be on the wrong side
. With the 338Norma you will certainly be able to shoot waaaaaaay over there.
Although I have no particular experience with the 338Norma, I would think that your go-to powders will be H1000 and/or Retumbo. The Hodgdon extreme powders tend to be better than others because of their temperature stability.
In terms of bullets, the 300grainers (SMK and VLD hybrid) are the 'standard', you might want to consider some of the good 225 or 250 grain bullets. They still have good BCs and will lower the felt recoil.