Correct me if I'm wrong, but military cartridges are also tempered around the neck and these show no signs of tempering. These look more like Walmart rounds than military.

All bottleneck cartridge cases (not just military) are annealed (softened) at the neck after they are drawn so they will seal the chamber upon firing. This causes the discoloration you describe Alan. If not, they are hard and brittle from work-hardening and could split and leak hot propellent gas towards the rear........never a good thing. These rounds, while they appear to be 5.56mm could have been found anywhere and polished up for the obviously staged photo-op for the clueless.

Our soldiers are are so good, now all we have to do is throw our bullets (commercially bought) at people.