Having made LOTS of 708 and 260 Rem cases out of Federal Gold Medal 308 I can tell you my experience. Typically, I make a neck turn pass on the 308. I then lube it with STP oil treatment and run it through a 708 die and then through a 260 die. I then make a final neck pass to final dimension. IF you only make your neck turn once it is already necked down, it will create a substantial 'donut' at the neck/shoulder junction.
I was really glad when Lapua made the 260 brass as the R-P brass was pretty crappy in my experience.
