Who crimps for the AR-15?
I do, I have anyway in the past for some loads. I have a taper crimp die for the 223, 308, 300 WSM just for the AR platform and when loading for full auto use it is a good idea. Also some claim better accuracy when crimped uniformly in brass of the same length.
Is there nothing so sacred on this earth that you aren't willing to kill or die for?
Ditto, and for hunting loads too. A Lee Factory Crimp die(s) work for me.
I load for a semi-auto. I don't crimp.