Above are two views of the .58 Minie ball that was the standard round for infantry rifled weapons during the Civil War.  In the picture on the left, notice the concave base which allowed the expanding gas from the gunpowder charge to force the soft lead of the bullet into the grooves on the inside of the barrel.  The .58 Minie ball has a diameter of .5775 inches and weighs 500 grains (1.14 oz. / 32.45 g.).  At ammunition factories greased .58 Minie's were wrapped in a paper cartridge that also contained 60 grains of black musket-grade gunpowder.  Four packs of ten cartridges was the standard ammunition issue to a soldier in the field.

      Captain Minie's original design for the bullet included a small iron "expander-plug" set in the base of this cavity.  Experiments performed by James H. Burton at the Harpers Ferry Armory found that this plug was unnecessary, and was omitted from the American version of the round.  Burton also added the three deep rings or "grease grooves" running around the cylindrical part of the bullet.  These rings helped the lead engage the rifling grooves when the bullet was fired.

      Burton would later serve as the Confederacy's Superintendent of Armories.