Three types of projectiles known as Williams Patent "cleaner" bullets were used by the Union Army during the American Civil War in the standard .58 caliber rifle muskets. There was a fourth developed for use in the Union Repeating or "Coffee-Mill" gun. The inventor was Elijah D. Williams of Philadelphia, Penn, who filed an application for his patent on May 30, 1861. It was issued almost a year later on May 13, 1862 but field trials on his "improved" bullet had already begun.