American Military History, Volume 1

At Davis' insistence the new infantry units were armed with percussion-cap, single shot, muzzleloading rifled muskets instead of smoothbore muskets. Nineteenth century technological developments had made possible an accurate, dependable muzzleloading rifle with at least as fast a rate of fire as the smoothbore musket. This was partly due to the application of the percussion-cap principle to the rifle and partly to the adoption in 1855 of the Minié ball or bullet, a lead projectile tapering forward from its hollow base. To load and fire, the soldier bit open the paper cartridge, poured the powder down the barrel, rammed in the paper to seat the charge, and then rammed the bullet home. He then put the cap in place, full-cocked the piece, aimed, and fired. Sparks from the cap fired the powder. The force of the explosion expanded the hollow base of the bullet to fit the rifling, and the bullet left the barrel spinning and thus with considerable accuracy. Its effective range was 400 to 600 yards as compared with only around 100 yards for smoothbore muskets. The rate of fire was a theoretical three rounds per minute, though this was seldom attained in practice.

In 1855 the national armories began making only rifles and started converting smoothbores into rifles, but the work took time. By the end of 1858 the Springfield and Harpers Ferry Armories had manufactured only 4,000 of the new type of rifle, the Springfield .58, a muzzleloader. Breechloading, permitting a much more rapid rate of fire, had to await the development of a tight-fitting, but easy-moving bolt and a cartridge that would effectively seal the breech. Many breechloaders were on the market in the 1850s; and the Army began testing all available models but did not complete its tests before 1861. Effective breechloading rifles required metallic rather than paper cartridges to prevent escape of gases at the breech. Metallic cartridges were invented in 1856 but were not produced in large numbers until after 1861.