BACKGROUNDAberdeen Proving Grounds (APG) is approximately 50 km northeast of Baltimore, Maryland and is a designated Major Range Test Facility operated by the U.S. Department of Defense. APG is located on approximately 7,000 ha of coastal plain bordering the upper Chesapeake Bay. Since development and testing of weapons and weapon systems is a primary function of APG, about 80 to 85% of the land at APG is dedicated to ballistic test ranges, impact areas, vehicle test tracks, and other test facilities. Armor-piercing penetrators composed of a DU alloy (99.25% DU and 0.75% titanium) have been field-tested at APG for in-flight accuracy since the 1950s. DU has been used in armor-piercing penetrators because of its high density, good mechanical properties, pyrophoric qualities, and relatively low cost.