Personally, the concept of "squeezing" a magnum cartridge into a standard short action AR receiver is a losing proposition from the get-go IMO for the simple reason between the datum where the barrel extension ends and magazine well depth (clearance front to back) will never allow enough cartridge length to truly exploit maximum efficient use of modern very high BC bullets. I've spent a lot of time dickering with them and trying, it becomes a musical chairs of tuning and grinding. Sometimes I wonder if the "fatty" magnums are chasing the dream of a "supersized" reincarnation of 6 ppc.
Although it means paying a $1,000 or more premium over what you could do yourself, I'd look at biting the bullet and buying the noreen 30-06 carbine at around 2K to get my foot in the door with the receivers and then have the option to reconfigure to other long action cartridges. Now a 280 AI AR--that gets me excited. Or maybe find someone to go into business with making them yourself, though others have tried and so far doesn't look like anyone has made much of a market out of it at their high prices.