I had a 6.5-06 Ack. and I originally used 270 brass for the longer neck. If you don't want to trim the necks, the 25-06 brass is the way to go. Just run one through a FL die and be done with it. If you want to taylor your brass then the 270 is the way to go. I ended up going the latter in the end. I did eventually sell the rifle but if you need any information I'd check my notes.