Summary - Who Wins?The .260, 6.5x47, and 6.5 Creedmoor have almost very close ballistic performance. Factory ammunition for the 6.5x47 Lapua is down 100-150 fps versus the .260 and 6.5 Creedmoor, but an experienced reloader with a strong action can match or exceed their performance with hand loads due to the strong case design. I wasn't able to test the 6.5 Creedmoor in an AI-AW like the .260 and 6.5x47. My best guess is that it would match .260 Remington, but the variance would be within what we see barrel to barrel. For the same pressure, the .260 and the 6.5 Creedmoor will have an about 100-125 fps advantage over the 6.5x47 Lapua, with the 140-gr class bullets.
What will I do? Because of the primer issue in the AI-AW rifles, I get better ballistics from .260 than 6.5x47. I'm going to keep shooting the original Rock Creek / GA Precision .260 barrel until it's toast, and then look at which of .260 or 6.5 Creedmoor has better brass for a cheaper price for the next 6.5 mm barrel.
November 2009 Update!
In the end, neither of these new upstart cartridges did anything for me that the .260 didn't. With the new Reloder 17 powder, I am now launching the 139gr Scenar at just over 2900 fps from my 26" Rock Creek barrel. Some of my associates are shooting a load using this powder at 2980 fps; however, the large firing pin hole in my AI-AW does not allow this.