I was sectioning a bullet pulled from a 7.62x39 round of unknown origin for a board, when lo and behold, instead of a lead or steel core, I found a hollow in the nose filled with small plastic beads. Headstamp was 31 16. I've been able to find out that it was some sort of experimental round, but other than that, nothing. Does anyone know anything about them? The one on the far right is what I'm talking about.