Confederate forces destroyed the Harper’s Ferry armory in West Virginia at the beginning of the Civil War (1861-1865.) The Springfield armory in Springfield, Massachusetts, thus became the only United States government small arms manufacturing facility. Springfield rifle-muskets like this U.S. Model 1861, became the principal weapon of the Union infantryman. The spiraling grooves, or ‘rifling’ on the inside of the barrel forced a new style of bullet, called a “Minie ball”, to spin as it was shot, resulting in far greater long-range accuracy than the old smoothbore muskets of the American Revolution and the War of 1812. A percussion cap that ignited on impact by the gun hammer replaced the old flintlock system. A vigorous industrial base and large labor force allowed the Union to make ammunition and weapons in far greater quantities than the Confederates could produce.