Blood-

Congratulations.
You'll find soon enough that the .458 isn't anything of the recoil beast many folk assume it is.
That Hornady model #4502 is a fantastic bullet.
I run it at 2400+fps in my Whitworth Express rifle. They're accurate, dependable, and cheap.
Buy a box of 500 so that you get a pile all from the same lot.
That way you can develop your accurate load and forget about it.

Take a look at downrange performance of 350 vs 300 grain bullets, notice how much more energy the 350 keeps further out than the 300 does.
I'd thought of having numerous bullet weight loads for the .458, but since the #4502 is so consistent and accurate, I quit screwing around with the others once I got my 2400+fps load, and left it at that.

Have fun with your new rifle.
Let us know how it does for you.

--Tinker