I’ve also seen what happens when lead bullets strike hardened steel plate… and it isn’t pretty.
Lead fragments and splatters and flies off in all directions, essentially grenading and sending potentially lethal fragments in multiple directions. Because of this tendency of lead bullets to fragment, it is imperative that body armor be able to not only stop an incoming bullet, but capture it to prevent fragmentation wounds.
AR 500 Armor recently ran a test to demonstrate how well the anti-spall, anti-fragmentation Paxon coating on their AR 500 steel armor contains the slug after it strikes the armor.
I have to say that I’m rather impressed with the results.