Seems like a .45 wadcutter of iron rod would have a nice meplat in a .50 sabot. No deformation of bullet tips. No concern about expansion. No health related lead concerns. No pollution related lead concerns. Biodegradeable. Can't be any worse ballistically than round balls. Can't use a bullet puller, but with CO2, you can eject the bullet. Might be some corrosion issues. Not that I have the resources to cut/turn these. But iron is cheap enough if you can fabricate it.
Do anyone do this?