Well, there just might be a reason why Lake City, Black Hills among many others put a crimp on their 223/5.56 brass. Whatever the reason, it just might be a good enough reason for some of us to put a light taper crimp on the 223 used in an AR.
I feel that the 223/5.56 doesn't generate enough recoil for one to be concerned about bullet set-back, but there could be a slight chance of bullet pull when the round is chambered, if not taper crimped just a tad. I wouldn't use more than a 0.002" taper crimp on the 223/5.56, if you decide to crimp.