I don't know what you think that proves? Are you insinuating that no gunsmiths know this and incorporate it in their builds? are you insinuating that without the "proper .004" setback in headspace will render the firearm useless? Clearly there are people running AI in AR's. I am trying really hard not to bash you, but you have brought zero to the table and zero to defend your claim. So what exactly are you saying? I am sitting here scratching my head.
I don't care you can be more interested in group forum pack mentality or you can learn something. what I am saying is YES! there are many gunsmiths who don't properly set the barrel back when they are modifying an existing chamber to ackley. I posted a link to the set back I mentioned from PO ackleys book. as to zero to the table, did you read why this crush fit is needed? go back and read what I said. the same thing applies to a fresh newly made ackley chamber, THERE MUST BE A CRUSH FIT, the headspace must be shortened to do it properly. get mad all you want say I am full of it. google ackley chamber crush fit and do your own research on the subject. the brass is gripping the sides of the chamber this causes the brass to stretch at the back instead of the front of the case, upon firing. This is why ackley shortened the headspace on his chambers when they were recut to ackley. its improper to simply run an ackley reamer into a chamber without the set back. my point was I don't think crush fit and smaller headspace is a good idea in an AR 15. I was bashed by the know it alls on here.
