in a word NO there pretty much isn't a way to do a 223 AI in an Ar 15. The reason is when an ackley chamber is cut and if its done correctly they actually tighten the headspace .004" over a standard 223 round. this is called a crush fit, and its a resistance you should feel as you close the bolt on a piece of brass in an ackley chamber. granted many gunsmiths don't even know they are supposed to do it and the reasons why.
the problem with not shortening the headspace below that of the standard round when you go to fireform the brass the case initially expands sticking to the chamber walls instead of the brass just flowing forward it flows back stretching the case where you DO NOT want it stretched. this can lead to case head separations. I have a 280 ackley that I am just getting around to getting setup after a new barrel. apparently there is a difference between the headspace on hornady 280 brass and nosler. the hornady is shorter, I tried forming a case with creme of wheat and found I had a slight protruding primer. This told me right away I had too much headspace for that brass.
that is the long version, if you could somehow by brass that was preformed and the chamber cut just to it then you could run a 223 ai in an ar 15, but a crush fit on the brass aint going to work in an AR for obvious reason. if you are looking for more umph in an ar 15, I would recommnd the 22x6.8 or 6x6.8 black hole makes barrels already for them. I would do it myself but I lose too much brass and 6.8 brass isn't that cheap. one day I hope they standardize with plug and play parts a high compacity ar 15 cartridge. something along the lines of the 6.5 br case in compacity.
