"Copper-washed" ammo is not only that in many cases (so to speak).

If you look closely at a fresh round, you will often notice that the extractor groove is "darker" than the rest of teh case.

This is caused by the LACQUER top-coat, "building-up" there.

This tiny film on the case, especially around the necks, gave me the horrors whist working on the early AIA M-10 carbines.

The green lacquered stuff seems to be actual "Mil-Spec" and the "chocolate brown" lacquered Chinese appears to have been made as a purely commercial "export product"; the lacquer often flakes off the neck area after firing.

Late production "grey" / "polymer" coated stuff seems to hold up better.
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