Congratulations you are on the way to a new barrel. The 243 has always been a favorite but if I were setting up a new barrel now I would probably go 6mm Creedmoor. The CM has practically the same capacity as the 243 but the longer neck and better case geometry should contribute to longer barrel life and more uniform pressures. Not sure about the carbon build up probably only slightly less than the 243.
Have to somewhat agree with you, just not a big gaymoor fan, I would go with a 6mm Remington with a 1-8" twist but would have a hard time going back to a 243 Win
