New rifle what caliber should I choose?

[z987k]

But brass.....if it doesn't survive.......

You just buy a barrel worth of brass. Since peterson makes it, it's good brass. I'd imagine a box of 250 would cover it.
If I do a cartridge that isn't insanely well supported, I do that. Then it's never an issue.

 

[Huntnpack 2]

6.5-284 super easy to load for, accurate, low recoil,
Long brass life. Several powders work well.
Love’s the 140 Berger’s. Absolute Joy to shoot.