The only AI cartridge I have any fireforming experience with is the 30-06 AI, but what has worked best for me is a crush-fit at the neck-shoulder juncture and a heavy bullet with the fastest appropriate powder for that bullet weight. I used 180's, since I had a lot of them. The brass shortened, to fill up the available space in the chamber. This is what we expect to happen. I attained the "squash-fit" by necking up the brass with an 8mm mandrel ( the next size increment up from 30 caliber ) and then necking it back down to accept .308" diameter bullets, to attain that crush fit in the chamber. I recognized that I had a head space problem from an incorrectly-executed chambering job, and dealt with it by making the load fit the chamber. It worked, and I had the chamber fixed later. For one hunting season, though, I used the gun with the band-aid fix, and it worked just fine. ( I killed a big muley buck in eastern Montana who never knew that he was shot with a bastard rifle. Then I got it fixed, and it is correct now. It doesn't work any better, but nobody is gonna blow himself up with this gun if he puts factory ammo into, due to an excessive headspace issue.)
I used to think that that it didn't matter what happens, as long as t works - even if I get rid of the thing. Well, it does - things aren't like we would like them to be out there, and we do have to think about what would happen if some moron comes into possession of our pet wildcat project. If he blows himself up through his own ignorance, It's YOUR fault. If you're dead, your heirs get to pay for your "neglect." So, I guess the answer is don't build anything that some idiot could turn into a lawsuit against your estate. It kinda sucks, but that's the world we live in. Ackley-style improved chambers are a bit of a crap-shoot, on a good day. On a "normal" day they are introducing a lot of variables that have to be dealt with, whether you like or not. Die/chamber disagreement are the least of your problems - I approach my shooting with the same idea I used as a filtering device throughout my career as an airline pilot, which was to ask myself whether or not I could defend my decision on the matter if I got called into the chief pilot's office over a decision I had made in the cockpit. If it would work with an airplane, it will probably work with a rifle. Turbojet aircraft and high-performance rifles are very similar tools to operate. Anybody who hasn't had the difference between them demonstrated to him is either very lucky, or he is short on experience. We like to think that rifles are simple tool, but they are not in the eyes of the public - they are like spacecraft when you get into the courtroom, and the only expert is the lawyer. Do you trust that bastard ???
We know what works with a rifle, but what will keep you out of legal trouble is what we should be considering. If you're trying to wring out the best performance of your Ackley-Improved designs, don't document your work. Keep it all lawyer-proof. With factory cartridges, there is published data, all pressure-tested. With improved designs and wildcats, it's all subject to interpretation, and that interpretation is probably not going to be done by somebody who knows anything about the subject matter - he's going to be an "expert" on how to burn you in the legal arena.
So, after telling you the best way I've found to fire-form Ackley Improved cartridges, I am advising anybody who will listen to stay the hell out of the way of the lawyers. Published data on factory-loaded cartridges are the best way to do that. As much as I like the performance of my 30-06 AI, I would much rather just get a 300 magnum and cheat some ambulance-chancing lawyer out of the money he was going to sue out of me or my heirs over an extra 150 feet per second of bullet velocity.
