I do not yet reload, so factory ammo may be a factor. It is my intention to start reloading for .450 Bushmaster, 9mil luger, and whatever rifle is decided upon, but currently I have no equipment, and very little reloading experience. (Mostly watching others).
That .224 Valkyrie looks interesting, but nearly as expensive to shoot as the .450B. Hopefully, reloading will make ammo a bit less expensive.
Grendel has also crossed my mind.

An unemployed Jester, is nobody's Fool.

the only real difference between a good tracker and a bad tracker, is observation. all the same data is present for both. The rest, is understanding what you're seeing.

~Molɔ̀ːn Labé Skýla~