I’d add that those 5.56 cases are annealed to harden the neck and “leade.”
The reason that there is so much misinformation about the subject is that misinformed people like yourself keep adding their tripe to the pile.
Cartridge shell cases are not annealed to harden the neck. Just the opposite! Neck annealing is done to eliminate residual stresses in the neck and shoulder so that stress corrosion cracking will not occur over time. The annealing process actually softens and weakens the neck.
Most all rifle bottle neck shell cases are neck annealed which discolors the mouth and shoulder in the process.
Commercial ammunition manufactures typically removed the discoloration with a vigorous wash to make the shell case bright and shiny. Military shell cases are required to leave the discoloration to visually prove that the shell cases were in fact annealed. The "leade" in in the firearm chamber and nothing done to the shell case affects to rifle.
Please do not post misinformation on this forum.
Annealing actually softens the case. Allowing it to expand slightly and seal the chamber better.
.223 cases are usually annealed also, but are polished after annealing to produce a more appealing cosmetic finish. NATO specification requires visual proof of annealing which is why they are not polished.
It is not possible to anneal the "leade" which is a dimension and not a piece of material.