I can understand Tomme Boy's point, the weakest part of the reformed case is going to be the rebate wall section nearest to the head.
That leads me back to my oft repeated recommendation to buy the Graff & Sons range brass at $17/hundred, which is as safe as houses to reload.
I also received PMs saying that the Guns and Ammo says that "(repeat large chunks of the article as needed)" and because it is G&A saying it, it is considered gospel to a lot of folks. I would say this article is a fair enough write up of the development history of the thing, and as such it is OK enough, but please don't count on it as a case making reloader.
The Guns and Ammo article has simply lost track of the reloader's perspective. This is why many (myself included) say it is just plan wrong as things really sit today.
A parent case to a reloader can be used to SAFELY MAKE the new case with a simple neck job up or down. "The little fatter web and relatively smaller mouth was done so Winchester could get enough taper into the case to assist better feeding" is so TOO TOO much of a change to make in a 5.56 case such that it cannot be used to safely make the new brass by just using neck work, even when followed by fire forming which isn't mild at all BTW as you need enough gas pressure to operate the AR action. That much gas pressure moves the brass too far too fast and it cracks and splits it open near the head.
Remember this point please, the final fire forming step is soooo much movement up near the case head that heavy wall section cracks and splits (see video above) and all that fires gas back through the relatively open AR system while being too near the operator's face. Scaring the snot out of him even if it doesn't get his cheeks dirty.
By turning that fire forming "ballooning action driven by violent gas pressure" into a controlled cold forming set of die steel operations, perhaps we can come up with a way to make 5.56 brass into a slightly shorter than spec 350 Legend that is good enough for cast bullet pressures. We shall see.
I have over 800 cases partially processed to play with, and that is my reward for doing so.