I haven't played with .223AI, but I play with .243AI a lot! What I've found is that if I chamber a factory round in my AI chamber, the round goes off just fine and the bullet goes where it's pointed. The problem is that my fireformed case has the beginning of case head separation. Sometimes is't just a flat spot in the taper of the brass near the case head, sometimes it's a recess. It's because of improper headspacing. If you've got a setup that will allow you to seat the bullet into the lands, you can do that and headspace off of the bullet instead of the shoulder and that will properly fireform you're brass. In my case, my bbl is a 1 in 14" twist. 100 gr. bullets can be seated to the lands, but they give 3" groups, so it's a waist of bullets, primers and powder to make cases.... Heck, they aren't fun to shoot either! 55 grain bullets won't come close to the lands, so that was out. What I have to do is neck the round up to .270 and then partial size the neck back down to .243. That gives me a bump in the shoulder that I can headspace off of. The result is that I get good groups because I'm using the right bullet weight for my bbl and I get properly fireformed brass because I have proper headspacing. Getting that first round loaded and ready to go is a pain though, because you have to size it down, check the fit, size it down, check the fit... until I find the right amount of neck sizing to just barely fit the chamber.
As I said, I haven't played with .223 AI, but having gone for the .243 AI, I've never regretted the chambering.
Coyoter