Again, this question of the significance of Colour of primer seals vis-a-vis actual loading rears its head.
As I mentioned on another Post in another board, a lot of times, the colour of the primer seal in NOT of any significance (Just look at the US example (Red and Black lacquer on 30/06…jost depends on year, and the supply at the particular time); other (European makers, such as FN) are the same. Of Course, NAT) ammo uses a simple method, following of all things, German practice (Ball is green, Tracer red), yet Blanks may be green or red, (TIP colour).
As to the Chinese practice, here in Australia, we too have imported millions of rounds of 7,62x39, of strictly Military origin ( Plain Military Spam-cans…I call them “sardine tins” from their wind-off seal tabs in the older stock) and so-called “Commercial” ( 20 round packets) examples…the terms Military and Commercial, in Chinese Ammo situation, mean nothing…all Chinese ammo is made in Factories owned, operated and controlled by the PLA (the Armed Forces) so, the ammo is effectively, all “Military” (if it is “FMJ” which it most certainly is.)
Now “primer lacquer colour”…Chinese ammo uses various shades of red, from “pink” to deep wine colour, as well as yellow. I have found that the colour varies with the factory and the Time frame.
As to when the colour is applied, My only experience of Soviet Bloc manufacture of ammo is a Visit to Sellier & Bellot in 1993, soon after Czech division from Slovakia, and also its shrugging off of Communism a few years earlier.
Ammunition in all the “Russian” calibres was being made on Russian style machinery, with Russian style production processes. The grey steel cases were lacquered after loading with the typical primer seals and neck seals; then the entire cases was given its clear lacquer coat by a dipping process
(Body Lacquer necessary for Bonderised steel cases); as well I observed in the "Commercial brass cartridge side, that their Pistol ammo was all Primer lacquered by small, hand operated transfer Pads, after complete assembly and “trayed” already into 25 round box trays ready to be slipped into packets. very labour intensive, but that was a hangover from the Communist days.
Now I don’t know how much of this Eastern Europe (Soviet) practice is transferable to China in our interpretation, but I would say, knowing a bit about Communist Psychology, that even though the Chinese had a falling out over doctrine with the Soviet Russians back in 1959-60, that would not have affected such mundane technological matters as Primer lacquering…
And having observed thousands of (fired) cartridge cases from the 1960s to the 1990s of 7,62x39 of Chinese origin ( Coppered Steel, Green case lacquered steel, Chocolate coloured Laquered steel) I would say the two major colours used are Yellow and Red (various shades) and that they were used on Ball cases. Thus NO relationship to other indications of “Special” or specific types of loading.
The Function of the lacquer its to seal the primer cup to the case, for Moisture proofing. The red or yellow colour is to Indicate Postively that this step has been done (Just like the Anneal colours on brass case neck and shoulder which on Military ammo are NOT Polished away…a QA indicator for acceptance protocol, dating from the 1920s ( Tsarist ammo from WW I–see Frost " The Manufacture of Ammunition" (NRA Publ.).
Also, whether the primer is completely covered by laquer or not is a function of the amount of contact by the applying head, not any indication of cartridge loading. Same observation in thousands of ball cases.
(I will add here that in making Blanks for the Movie Industry, we recycle the standard Ball case (Steel) with new Berdan primers, and simply Crimp ( “star rosette”) into a short blank, which works OK in various SA/ FA rifles; for some applications we do use “Factory” Long profile Blanks. But for economy, the short blanks still fill a major part of our 7,62x39 Blank requirements.
The cases come very cheap from Rifle Club ranges, as they are simply discarded otherwise to rust on the ground. ( about 5 cents a Kilogram).
Maybe later this year on a business trip to PRC I will get to see a production line of "Chinese " ammo, and observe the process of primer Lacquering.
Regards, Doc AV