I'm unsure if 260 Rem is larger or smaller in case capacity than 6.5x55, but Hornady #3 lists 3031/100s in 6.5x55 as 33.8 @2500fps to 38.3 @ 2800fps. That should get you in the ballpark anyway. I've used 3031 from 22-250 thru 35 Whelen with good results. It's a very useful powder. Long & crunchy, but useful.

Sacred cows make good burgers when you know what temperature to cook them at.-Rev. Billy