All that to say:

If I was building the gun, I?d go with a long throated .260 Remington and handload from easily available and inexpensive .308 Win brass or proper headstamp if desired. I?d seat heavy for caliber Bullets long and let the gun tell me when to stop stuffing powder. Not a generic loading manual. I?d get as much velocity out of the platform as meets my accuracy requirement and go forth and conquer.

But again, I care little about factory loads. I can beat them all with judicious handloads designed for my particular platform.

You just have to decide your priorities.

Oh, and there would be a brake on the barrel.