Quoted:
223 wylde chamber
Needn't have posted anything else. Problem has nothing to do with headspace.
A Wylde is a target chamber, designed with the leade/throat area in front of the case mount cut to .224" - the same diameter as the bullet. Just had another thread on the Wylde chamber tonight, and posted several informative links there:
http://www.ar15.com/forums/t_3_4/568070_wyldie_chamber.html
Depending on the ogive and seating depth of the bullet in question, some bullets will start to engrave into the throat when chambered (others will be very close to doing so). That .224 interference fit is good for precision, since the bullet is completely controlled from the moment it starts moving forward from the case, but bad for user-friendliness because you can't easily eject a live round. There is a lot of mechanical disadvantage in the extraction sequence on an AR15, so it's very tough to overcome that friction when extracting a live round from the chamber. Empty case ejection is not effected at all.
Solutions are: change barrels, shoot more to get a little throat erosion to relieve the interference fit. If it's an unlined/untreated steel or stainless barrel you could have the chamber recut to something with a slightly larger throat. Couple of other options depending on how much trouble you want to go to.
If you don't believe me, after you do the buttstock-slam ejection, take a look at the bullet... about 1/16" to 1/10" in front of the case mouth, you will see a ring around the bullet where it's been pressed into the freebore. Different styles of bullets that have a different shape may be slightly narrower there and will eject normally. XM193 was one of the tightest fitting ammo that I found when I ran into this problem.