Pretty much narrows it down to Hornady or Nosler. Federal is so invested in 224 V I can’t see them pursuing a 6 mm/243. Hornady was first to help SAAMI the 6.5 Grendel and would be my bet for a 6 mm using the 6.5 Grendel case. It’ll be interesting to see if they go with the Turbo or pure necked down 6.5 Grendel case.
I don’t see any viable reason to go with a 6.8 SPC or 5.56/223 case.
I don’t see any viable reason to go with a 6.8 SPC or 5.56/223 case.

