I had one. Wish I still had it. It was built by Lex Weberbeck of Rifles Inc.
Have a look at his website. It's a good one. Has a video of him building a custom rifle. The gun he built for me weighed under 5 lbs, has a 26" Shilen match grade stainless barrel. He has his own design composite stock which is a real dream to hold. But don't get too excited by his so called quiet brake.
It works but you will be deaf for a while after shooting it at an animal.
Anyways, The .280 AI is an awesome cartridge. It will shot right with a 7mm Weatherby. The pain is fireforming the cases. Maybe today one can buy them. I used 140gr Nosler partitions in it with RL19 powder. One hot machine!
I loaded 10gr of pistol powder (BLC2) then filled the case with corn meal.
On top of this drop a bit of bonfast glue. The cases foreform real nice. The
neat part of a .280 Ai is that you can used .280 ammo if you want.

Best wishes in 2011.