I am currently in the same boat.
I am talking to a local rifle builder about a rifle in either 260Rem, 6.5C, or possibly 243. I'm looking for a relatively flat shooing bullet that will help me beat a buddy of mine at 300 with the possibility of further if I can find the time to drive out to PA at some point. If I do a 6.5mm I am then between the Tikka Tac and having a rifle built. This thread has been helpful as I am just betwixt and between all of them.
C
Creedmoor brass is a bit difficult to get: Terry Cross' advice made my decision to go with the .260 Regular.
I thought I wanted a 260AI, but all things being equal, (pressure), there's not that much difference between the 2.
I'm shooting for the moon on velocity: my goal is 2900fps with 140 Bergers: 2800-2850fps isn't something to sneeze at though, according to Ballistic AE.
700 LH SA trued and blued
26" Hawk Hill 4 groove barrel.
Badger Ordnance Bottom Metal- fingers crossed on COAL.