I confess that I don’t know a lot about these cartridges either. I believe there are forum members who actually used them and maybe they’ll give us the scoop.
What I do know is that they were used to train gunners, mostly during WWII. Just before firing, the cartridge tips were dipped in a pan of colored ink. A different color for each individual. When the bullet passed through the target it left a smudge of the ink. Instructers could tell which gunner had hit the target by observing the smudges.
( Many shooters today do the same thing when shooting at long distances, such as 1000 yards. One difference is that we use Magic Markers and each shot has a different color tip. We record the sequence of shots. When the target is examined we can see exactly where each shot hit.)
Since most of the marking cartridges were used up, they are not that common. Plus, the dried ink was very fragile and soon wore off. So, a cartridge with just a vestige of ink could be mistaken for a tracer, or an incendiary, etc.
I do have some that were definitely tracers. I pulled a few bullets to verify. The original red tips were covered by the ink so the only way to tell that they were tracers was by weight, and pulling the bullet.
I have one short linked belt of the cartridges and I assume they were used mostly in MGs although it doesn’t rule out their use by Riflemen as well.
I can’t explain why Chris would not mention them. Or HWS. I suppose because they did not have any official designation and were field mods only.
And that’s all I know about that.