I guess when 5.56, 6.8, or 6.5 Creedmore won't do...
I'm sure there's a point to this somewhere. A specialized, niche requirement maybe?
"Barrett, Hornady and OSS have now confirmed that they have partnered to provide the US Department of Defense with a new rifle chambered in 6mm ARC."
https://www.thefirearmblog.com/blog/...m-arc-program/