Combo of slower cycle speeds, and the larger neck size of the case.

At unlock, the bolt starts coming back, and as soon as the neck section of the case clears the chamber, the ejector is already camming the spent rim off the bolt face.  So this means that the case is starting to be cam'd off the bolt face between the void of the chamber back edge, and the back of the barrel extension (void of the barrel extension)

So with a smaller 223 size neck on the case, there is more of a gap for the pull and the neck to not make contact with the inward edges of the barrel extension lugs tips.

As for on your rig, your not going to be able to speed up the cycle that much and solve the problem, so we need to attack the problem a different way instead.  The neck of the brass is still going to tag the two barrel lug inner points on the extraction, so what we need to do is round/de-sharpen  the inner tips of the barrel extension lugs on the 3:00 position of the two inner  barrel extension tips instead.


Take a look at the left barrel extension, and see where the arrow is pointing at the chamfer areas inside the barrel extension.  Now look more outward and notice the inner end of tips corner edges instead of the lugs.  These are the the areas on your barrel extension that you need to de-sharpen instead on the two corresponding barrel lug inner edges on your barrel.

If you need a land mark of what two lug inner lug edges to de-sharpen the tips with either a stone or some 400 wet dry sand paper, the top inner tip edge of the lug that that has the #4 just outside it, and the bottom inner tip edge of the lug just above it.


And no, do not try to remove the barrel extension from the barrel to de-bur the tips of the lug from the inside.  This will just cause more problems with trying to get the barrel extension to index and head space when you go to reinstall it instead.