I don't know about "
designed with the Grendel in mind," but Hornady Handbook #8 speaks very highly of the 123 gr A-Max as the best choice among their bullets for long range shooting.
For the price difference, I would just buy factory rounds. That way, you could shoot them for 30 cents and have brass you know for sure is "once fired". This is how I get my brass for 25 ACP.
Used Sellers, like:
http://www.diamondkbrass.com/6.5mm-Grendel25.html do try to stock Grendel brass, but even with them its still about 55 cents per round and you don't know if its on its first or fifth firing.
I have the unique experience of having brass with various headstamps that was stored in various ways when I was stricken with a disease that almost killed me and kept me from my reloading bench for nearly 21 years. Norma and Lapua brass suffered greater degradation from corrosion (in some storage methods, upwards of 35% had to be disposed of). U.S. military and U.S. domestic headstamps consistently performed better. I know both Norma and Lapua have reputations for making almost magical products, but as far as brass durability under a unique set of adverse conditions, their products failed to perform for me.