One tangible connection to the human cost of the Civil War can be found in the Frazier History Museum in Louisville, Ky., in the form of a beautifully engraved Henry repeating rifle, serial number 19. The rifles were highly prized on the battlefield. Confederates described the Henry as "that darn Yankee rifle that they load on Sunday and shoot all week." THE PROGENITOR of the Winchester repeaters, the Henry was a technological marvel in its time. It fired a .44-caliber, self-contained, metallic, rim-fire primed cartridge. The magazine held 15 shots, and one more could be loaded in the chamber, giving...