The US Navy defines blended-metal bullets as, "projectiles which utilize cores manufactured with materials other than lead, using processes other than melting." The solicitation elaborates as follows: The base metals used in these formulations are usually a very fine powder. Copper, tungsten, and brass are examples of some of the base powdered metals used to date. These powdered metals are mixed with a binder such as tin, zinc, or a polymer such as nylon. Once the powdered metal(s) and binder(s) are mixed, they are pressed or molded into the final projectile core form, and in some cases sintered.