"When Nosler came out with their 26 (264) Weatherby came out with the 6.5-300."
The 6.5-300 Wby was originally a wildcat round in the 70's used as a long range (1,000yd) target round. Nothing new.
IIRC, barrel life was extremely short.
It was originally called the 6.5 Weatherby-Wright- Hoyer by the people who originated the cartridge. I saw the article in IIRC RIFLE or HANDLOADER Magazine.
Paul B.