I have several,first I wouldnt go with a barrel that long.
What bullet would you like to shoot?
I have had 8 twist and 12 twist,they both will shoot great at 600 yds but with different weight bullets of course.
With a 12 twist you could also use it as a varmint rifle.
I always had tight neck chambers but now use no turn with a reamer made to tighter tolerances.
Lupua brass is that good.
Any more questions,just ask!