I think the thing to understand about the 6.5CM may have some relationship to my own history with the .260.
When I went to my first LR comp in 2002, I was shooting the .260, and was still quite a ways from understanding how best to handload for it, while also dealing with pressure problems in a big way using VV N-140 with Lapua 139 Scenars. Over time, it became obvious that N-140 was too fast and didn't have great temperature stability at the time, and also that the 139 Scenar tended to run higher pressures than its 140gr, and later 142gr brethren. My load (for a 28" barrel) evolved to be 43.8gr of H-4350 and the 142SMK or 140 A-Max. This came after extensive experimentation with Ramshot Big Game, and later, Hunter came along and was better. But as I said above, Ramshot powders were really scarce and soon I was unable to keep enough in stock to fuel my shooting activities. Folks here ordained H-4350 as the goto powder, and they were right. Experiments with H-4831(and -SC) showed better accuracy, but not such great velocity; and I dropped the project. Hindsight strongly suggests that could have been a mistake, and I will probably resume that experiment some day.
We were doing OK in comp with the .260 until the 6.5-284 dawned upon the field of competition. Dubbed the 'Fag Mag', it just blew away all the competition, and since it was also a barrel burner, it shifted the game closer to being an arms race with folks who had more money being in the driver seat. Not having more money, I was essentially done with LR comp. The lesson was that the .260 was good, but something better required more case capacity.
Then the 6.5 Creedmore was released. It had exceptional backing from Hornady, and gun makers learned the lesson that Remington didn't, they needed to put more support behind their new chamberings. The 6.5CM thrived on all that Mother's milk, and today we see it dominating the 6.5mm scene.
But that doesn't mean it's a better LR round than the .260. Going back to the case capacity lesson, more capacity was needed, but the 6.5CM went the other way, and bullet for bullet, it achieves less velocity than the 260 in equal length barrels in a game where less velocity is not such a great idea.
Well, I came to a realization about that, based on my own conclusion that as long as the bullet arrives ontarget at 1300fps or greater, velocity isn't king, wind skills is the real king. So less velocity is OK, IF you have the wind skills; and this brings my thinking back to H-4831. At this point, it's just thinking, but i plan to follow it up this coming season. My 28' barrel is ideally suited for that powder as well.
Now, then, about that Varget. When we stepped up to the LR plate for the first time with the 260 in 2002, we asked the old hands what was the best load for the .260. They'd all say 34-36 grains of Varget with a 140gr bullet. Hmm, interesting. Looking at the current Hornady manual, they are posting loads between 32.7gr and 36.4gr of Varget with their 140-143gr class of bullets for the 6.5CM. So maybe Varget isn't so far out of the race after all.
Greg