bw34,
Given your mention of the 6.5-06 Ackley, I will take this to mean you are not afraid of a wildcat. I hunted for a while with a 26" barreled 6.5 Gibbs as my go to beanfield rifle. I ran a #5 contour 1-10" twist Pac Nor barrel because I had no desire to shoot anything heavier than a 120 grain bullet. This was before long range shooting became as popular as it is now. It shot wicked flat with 120 Nosler BTs and 125 Partitions. It was accurate, but case forming became a chore (fireforming isn't really an option with Gibbs cases) and I was only able to get 3 to 4 reloads out of my brass before the short neck split. I sold the rifle and built up a 6.5-06. Loved it. Did everything a 270 would do with slightly less recoil. Again, unlike many who post here, I went with a slow twist 1-10" twist barrel because I had no desire to shoot anything over a 120 grain bullet. Then I moved on to the 6.5-06AI with a 24" barrel. Was everything the 6.6-06 was, just a little more. This one I built with a 1-9" twist to accommodate up to 130 grain bullets. Again, I loved it. I sold both after I was laid off. I had a brief flirtation with the 6.5-284 Norma. I built it with a 1-8" twist 26" barrel. Like Hotholds442 mentioned, I found it kind of finicky and never could find a load that provided me the accuracy I wanted so I sold it. Your experience and that of others may be very different. I flirted with the 6.5-280 AI for a little while as well. I liked the round, but eventually tired of the brass prep. I'm currently building a 6.5x65 RWS. The RWS round is not a wildcat, but brass is only made by RWS, is pricey, and can be a little difficult to obtain. However, its a hunting rifle, so 100 pieces of brass will last quite a while. Another round to consider, is the 6.5x55 AI. I like the original 6.5x55, but I hate trimming brass. The AI version slows down brass flow in my experience to the point that case trimming becomes minimal. Whether going AI is worth it or not, is a personal decision. One other oldie to consider is the 256 Newton. It has a case capacity between the 6.5x55 and the 6.5-06. Brass is made by only one company and again, it can be pricey and somewhat difficult to obtain.

At the end of the day, the question is how much time, energy, and funds do you want to devote to this project. As I get older, I find I like shooting more and doing excessive case prep less. To that end, I'm saving my pennies to have a reamer made for a 6.5-06 based on the 270 case. That way I can neck down virgin 270 cases, outside neck turn a little, load and shoot. Lots of sources for good 270 brass and it rarely goes out of stock and isn't too costly.

Just my 2 cents and I hope you find it of some value. Whatever you choose, I hope it works out well and keep us posted. I'm always interested in the builds of others and why they went the way they did.