I have an AR that has a .223 Wylde Chamber and I have another AR that is 5.56 Nato chambered. Well I was using my RCBS headspace mic gauge and compaired fired brass from the two chambers. The brass from my .223 Wylde measured .003 larger from the case head to the datum line then the brass from my 5.56 Nato chamber. Wouldnt you think the Wylde chamber should be shorter then the Nato chamber? I am not sure what to think on this. Maybe since the Wylde is a tighter chamber the pressure built faster and full expanded the case to fit the chamber where as the 5.56 chamber is larger and possibly did not expand the case all the way to fill the chamber? The gun with the Wylde chamber has a 20" barrel and the 5.56 is 16". I also used the same ammo in both guns, and both guns functioned perfectly with this ammo.
What do you guys think?