Why else would they bother with such a small hole in the bullet jacket? It can’t be for further identification - you can barely see it they are so small. I wish I had an extra to cut into. I assumed, since the plastic is even with the outside of the case and bullet at the various holes, that the plastic was poured into the assembled base and bullet through the primer flash hole (probably enlarged from its original state) while in a molten state. I can’t think of any other way the plastic could protrude into the holes and be so perfectely even with the outside case and bullet jacket walls.
But then, I admit, I know nothing about the manufacture of such products.
Frank, did you get any impressions of the means of manufacture when you sectioned one?