I cut open another of the 50 caliber armor piercing bullets recently given to me by a friend. I wanted to learn more about the nature of the penetrator core. I found that it is magnetic. It can be rusted to a degree. It is easily welded with the MIG machine. I believe it is hardened tungsten steel but I don’t know how to confirm that.
I’ll try this one out for a while and report how it holds up. The first core I peeled out I left in the original free state and it is now another pocket tool.