The original versions of these were machined bronze, but the "cop-killer bullet ban" outlawed those, so the next version was machined copper, as seen in the above photos.
I recall that the tube bullet left a particular difficult wound to treat and heal. It cut a sausage like entry, leaving a tube of cut flesh in you and lots of blood loss. Hard to clean and close. Also, the solid copper of some versions were vest penetrators.
I had a box of the PMC .44Spl. version around 1988. As I recall the bullets were ~140 gr. Shot about 2' low at 15'. Very inaccurate. They were called "tubular bullets."