Either 280 or 270 brass could be necked down to fireform into a 6.5-06 Ackley. Just adjust the die to the point where you get a "crush fit" when chambering the round which will eliminate any headspace issues you might have with your chamber to prevent brass stretch above the base/web.
You will have to trim the brass. You can fireform using bullets or COW.
Barstooler
