I've shot a 6.5 Creedmoor, very nice round. But with all the 6.5 rounds, grendel, creedmoor, etc. Most of those are hand-loads. I doubt most people shooting those rounds are buying off the shelf rounds, they're making handloads.
Pretty sure the record for longest shot is a .223 round though.
It depends whose "World Record" is claimed, but .408 CheyTac and .416 Barrett rule the roost at KO2M (King of 2 Miles) and the world record sniper shot was the Canadian sniper (I never saw his name published) and his .50 BMG McMillan TAC-50 at 2.2 miles.
If .223 holds any world record, it's probably one of those "in its class" records.
The popularity and increasing ubiquity of 6.5 Creedmoor (though not nearly as ubiquitous as 7.62 NATO) has cooled enthusiasm for the 6.5 Grendel, but it is still an amazing cartridge:
6.5 Grendel Cartridge GuideAccurate, Efficient, AR-Friendly Cartridge is Winning Converts
https://www.accurateshooter.com/cartridge-guides/6-5-grendel-cartridge-guide/ The 6.5 Creedmoor is a "better" cartridge than the Grendel, but it won't fit in the Mini-Mauser or AR15 actions and it requires much more powder, more recoil, and heavier rifle to obtain its performance.