Re: 6.5 creedmoor
You can use any of the 308 base cartridges, IE: 243, 260, 7mm-08and 308.
Some will take more steps than another.
I suggest you get a form die and a neck cutting die.
Lonnie Humble of Hornady recomended Remington 260 brass as a base brass.
You will find Lapua 243, and 308 to be better choices.