So what is the military supposed to use? I know they've got a hard-on for leadless bullets, but can that really be a general issue replacement? There's all sorts of considerations in changing to a leadless bullet -- sectional density, mass, terminal performance. I can't see leadless bullets being a good choice for long range work, they lose energy too quickly and are more vulnerable to wind drift. And if you try to keep the same overall bullet mass, you end up with a projectile much longer than a lead one. At that point you have issues like rifling twist rate, headspacing, and decreased case volume.
And the biggest consideration of all is cost. Copper is a lot more expensive than lead.