I've been playing with some Tungsten rod - available worldwide as welding electrodes - recently.
Thing is, I looked at a 6" x 3/16" rod, and wondered whether it would make a good penetrator.
I thought, fired as a subcalibre sabot round in a BMG, that it would penetrate all but the glacis plate of an M1A2 Abrams MBT. At nearly half a mile range.
Or maybe not, as people will tell me.