The 260 Rem idea intrigues me.
Can't find a whole lot on how it has done in F class or Benchrest matches.
I'll have to do some more research.
BR it is NON existent. In long range 1000 yard BR, the guys opt for the big boomers as the weight limits are a lot higher.
When you can shoot a real heavy rifle why handicap yourself with a small caliber light bullet when you could shoot heavy pills.
F Class I cannot answer.