Beyond the notable pistols and long guns featured in the American Civil War (1861-1865), the carbine grew in considerable use with both Union and Confederate forces. One addition to the ranks was the Merrill Carbine which first appeared in 1863 as a single-shot, breech-loading weapon. It was eventually used by both sides of the conflict and originated out of Baltimore, Maryland from an 1858 design attributed to James H. Merrill. The Union claimed more of the 14,495 examples produced but stocks still fell to the desperate South. Two major variants appeared during its rather short service life.
As a carbine, the weapon served as a short alternative to standard long guns of the period. In this way, with their shortened barrels and forends, the weapon could be relatively easily (and more effectively) wielded from atop a horse. As such, carbines served as primary issue to mounted infantry and could be as effective in the hands of foot soldiers requiring mobility.
The Merrill was designed as breech-loading firearm meaning that the ammunition was inserted through an opening presented at the receiver of the weapon. This was in contrast to the "muzzle-loading" weapons see prior which required the ammunition to be sent down the muzzle of the weapon (along with powder). The Merrill was limited to single-shot firing, a common quality of many weapons of the time, and was chambered to fire the .54 Minie ball bullet by way of a paper cartridge. A hammer set along the right side of the receiver was cocked back at the ready. Ahead of the hammer lay a small nipple to which a percussion cap was added. This cap, when struck by the falling hammer, provided the necessary spark to ignite the powder of the cartridge within the chamber. The expanding pressures then sent the bullet down and out of the muzzle end of the barrel. The percussion cap proved revolutionary for its time, replacing the 200-year old flintlock method which was heavily-influenced by environmental factors such as rain. The barrel of the Merrill design measured 22.25 inches in length.
The initial Merrill Carbines were noted for their standard features such as the patchbox fitted into the stock and covered by a hinged brass late. These became known as "First Type" carbines in the series. The pressures of war time production ultimately required a simplified version of the carbine and this resulted in the "Second Type" variant which lost the patchbox assembly. Copper was also added to the breech plunger for an improved seal at the breech. The breech lever latch was revised to a more rounded shape as opposed to the original's knurled form. There proved some variances in the lockplate design as well but the overall form and function of Second Types mimicked those of the First Type weapons already in circulation.
The Merrill Carbine served with both Union and Confederate cavalry units until the end of fighting in 1865. Cartridges were also manufactured in the South.