Two cartridges immediately came to mind when I read the OP's question. First was the 6.5 Swede, (obviously it came to mind for many) and the 6mm Remington.
I have a.260 on a short action and to tell you the truth, I wish I would have had a long action and just built a Swede. There is a ton of factory Swede ammo out there at reasonable prices. I doubt I would reload for it much if I had one.
I have been a long time 6mm Rem fan and continue to be. The 85 grain Sierra BTHP Gameking is my "Go To" bullet for this cartridge and I see no reason to change. From Jackrabbits and Coyotes to Mule Deer, that bullet drops them nicely.