“.....brass (copper and steel)?”
Brass an alloy of mostly Cu (copper) and Zn (zinc).
Hard to take Durbin’s word for anything. Illinois has offered up some pretty sorry senators. US Govt has surplussed brass for a long time, and has tried varying offerings ostensibly to get the best return for Uncle. If brass finds it’s way to the civilian market it gives the anti-firearms zealots an avenue to disrupt civilian sales they can’t achieve legislatively. Anyway, doubtful the so called cartels waste any time with US brass or firearms, but rather prob’ly get plenty of Russian or Chicom arms and steel-cased ammo at a discount.