The O.P. contains numerous factual errors, e.g.
* Tubb had nothing to do with 6.5 CM, it was Dennis DeMille
* .260 is hands-down better than .308 for long-range
but I want to correct the misunderstanding that stubbicatt posted because I have seen it repeated several times elsewhere (thanks for the compliment too by the way):
The dimensions of the cartridge allow one to seat a 140 without the base of the bullet extending below the neck/shoulder junction and still feed from a standard 308 length box magazine. There is some indication that this should increase accuracy.
The base of a 140gr will be well below the bottom of the neck, closer to the body/shoulder junction. When I was doing research for the article, I asked the engineer at Hornady about that specifically. Bottom line, this aspect is not a substantial difference compared to .260 Rem (if it were, I would have mentioned it in the article).