I called Hornady this morning. The salesman (Bob) said the .308 match brass is probably made by Winchester. Since Hornady brass is about %80 more in cost than Winchester brass, I assume their specs given to Winchester must be much tighter then off-the-shelf Winchester brass. Nosler in Oregon is still closed.
Since you piqued my curiosity, I called Nosler to see if they or another company manufactured their brass.
I spoke with Jerry in their Shooters Pro Shop. He told me that another company manufactured brass for them, using their specifications, and, when asked who it was, said that he was not at liberty to divulge the other company's name.
You might try asking the same question, and then make a comparison of notes.