Military testing new 5.56 projectile
Story here. The new projectile replaces the lead core with copper. (Heckuva situation when soldiers training for kill or be killed are expected to be environmentally conscious in the process).
I'm a bit skeptical, in that the article doesn't give any ballistics data. With a longer bullet, but needing to keep the same overall cartridge length, there will be less room for powder. A smaller charge and a faster burn would suggest that muzzle energy will fall.