Re: Forming .260 brass
you still have some variables to consider.
What parent case? .308 will need some reaming or turning or you'll have to fat a neck for a safe bullet release upon firing. Are you going to thin it before or after said sizing operation?
Personally I'd use WW 7mm-08 and size and go but I've yet to go that route so I cannnot give you a bushing number. I see that's what a lot of guys used with less fuss than my experiment converting some lapua .308's.