"No bullet could penetrate another bullet like that without the "target" bullet having a very solid support, and if it did, it would be severely damaged and/or blown well away by the impact. To get that kind of effect takes some mechanical intervention, probably in the form of something like a drill press (and a sense of humor)."
Well, there must have been tens of thousands of humorous dudes ignoring their wartime duties to crank out lots of joke bullets on battlefields around the world, because there are literally THOUSANDS of such collided bullets recovered from battlefields all over.
One only needs to google collided bullets.
Bullets aren't particularly tough, especially WW I era bullets that didn't have steel penetrators in the cores.
The drawn nose of the jacket is more than thick enough to prevent malformation when striking the thinner jacket along the body of the bullet. So, I have to disagree with your view that the bullet hitting another bullet would necessarily be obliterated or even severely damaged. There's MORE than enough proof from battlefields around the world to show that that's not the case.
Here are just a few that I found in a momentary review...
