"The U.S. Army Environmental Center began a program in 1997 to develop alternatives to the toxic lead that is used in the hundreds of millions of rounds that are annually fired during conflicts and at its training ranges. Carpenter says that although bullets using nanoaluminum are ready to be field tested, the government has been slow implement the technology."
I'm sorry but these two sentences don't make sense. Nanoaluminum increases the rates of certain Redox reactions. While this may be a useful adjunct to a bullet propellant, I fail to see how this will overcome problems with toxic lead per se.
---neither is the lead in the backstops at firing ranges toxic. It simply stays put with no real environmental effect--