XM Length Magnum BF Build-What Caliber?

[MasonfromWi]

So I have an XM magnum bolt face action coming as part of a trade deal and I’m wondering what caliber you all would go with if you were me. I already have 2-6.5 PRC’s and will soon have 2-300 WSM’s, I was thinking 7 SAUM but but from what I am seeing brass is very hard to come by. What else would you guys recommend, it’s going on an Element 4.0 mag chassis and my wife will likely be using it primarily. TIA.