My understanding, is that the difference is mainly due to the depth of the throat in the chambers. The Wylde chamber is throated deeper for the heavier bullets, because they are seated further out, and won't cause an increase in chamber pressure if the bullet is touching the rifling. Therefore it is safe to shoot military rounds or 223 civilian rounds in a wylde-chambered gun. Personally, I don't think it makes much difference, since military 5.56 rounds are loaded 10,000 PSI hotter than 223 rounds anyway, and I load mainly 55 grain bullets, so COL is the same either way. The Ogive of the heavier bullets might be different, though...