And .280 A.I. brass can be purchased already in A.I. form.
Not right now. I cannot find anyone with 280ai brass in stock, and haven't been able to for months. I'm guessing the manufacturers are focusing on the more mainstream rounds. I even considered fireforming from 280rem brass but can't find it either.
In response to the OP's post: I love my 280ai, mine is a custom built Encore, I had it built for spot/stalk hunting in the mountains so I chose the Encore platform, no action results in a lighter and shorter rifle that a repeater. My Encore has a 26" barrel and is still shorter than my '06 with a 24" barrel. But since that's not the topic, I digress.
I have hunted Texas game primarily with a 708 for a few decades, and while I have zero complaints about the 708, I have come to love my 280ai just as much over the last 10yrs. I run cup and core bullets (Sierra GK) thru the 08, they just seem to perform better on game at 08 velocities. I run 160gr Nosler AB's thru the 280ai as the added velocity seems to make them function better on game. I tried them in the 08 and just didn't seem to get the expansion they show at the higher speed the ackley produces. The 160gr AB from the 280ai on deer or hogs seems to be just the right combination of bullet construction and speed to crate a nice wound channel without destroying everything within 6" of the wound channel like a typical cup/core bullet can, and it retains enough weight to exit with monotonous reliability. I have never recovered one.
For reference, as mentioned above I have a 30-06 as well, and while any of them will kill a deer or hog just as dead as the 280ai, I just like it better than the '06 for some reason. I do not get into the long range stuff, but if looking to I would not hesitate to build a 280ai for that purpose either. The Encore is a very functional platform within its limits, but it will never be an optimal benchrest or long range precision platform. The 280ai is an extremely versatile and efficient round. And sure, you can load it pretty warm and start approaching factory loaded 7mag velocities, but start handloading for the mag and the gap widens again. So an Ackley will never be a 7mag no matter how much anyone wants it to be one. Again, being on the single shot platform I do not push the limits the of the round due to stress on the frame and hinge pin, but I get respectable velocities from it.
If I had to do over again, I would not hesitate to build another 280ai. Just wish I'd have stocked a bit more brass for it before the stupidity we are presently experiencing.