Agreed. I have six rifles chambered in 6.5 Grendel (4 ARs with 12.5", 16", 18", 20" barrels and 2 Howa Mini Actions with 20" barrels). It's not what he seeks.
I concur with 6mm ARC as the best suggestion. I just built a 22" 6mm ARC AR and next up I'll be rechambering one of the Howa Mini's as well.