I love the .280 AI, but didn't suggest it since you seemed adamant about easily finding ammo on the shelf. If you build an original Ackley version of the .280 AI you should be able to shoot factory ammo no problem, but I have been told the new Nosler/SAAMI spec .280 AI is .014" shorter, so stuffing factory loads in there might not fit. But if you already have a reamer to match the dies you were using before, you should be good to go.
I am wanting to build one of those very soon. I was going to build one out of my Browning A-Bolt II 7RM, but since I can't seem to find a standard bolt head anywhere, and Browning is wanting to be a bunch of punks about selling me one, I decided to just go with a .264 WinMag. Since I have almost all the parts for that (minus barrel blank) I'll go ahead and get it built. However, once I get a couple more actions for my builds, I'll be ready to start my .280 AI and .300 Ackley builds.