The American Civil War (1861-1865) saw a mix of gun technologies in play but there was a clear movement towards percussion-based, full cartridge, rifled breech-loaders which succeeded the older flintlock, ball ammunition, smoothbore muzzle-loaders. Some rifled breechloaders managed to see widespread production and service while others languished through limited numbers and appropriately restricted reaches. The Greene Carbine was one of the latter, a breech-loaded percussion-based carbine weapon of .54 caliber developed prior to the war during the early-1850s. When the carbine failed to impress U.S. Army authorities, it was sold to the British government though it is thought that some managed their way back to the United States through resale by other parties. The guns were known to be fielded by the 6th Ohio Cavalry of the Union Army but its numbers in the war were nonetheless limited.
The Greene action was patented and developed by one Lieutenant Colonel James D. Greene of Cambridge, Massachusetts (it is not known if the rank was an official military title or self-imposed). A hinged breech system was used which was locked by a twin-lugged rotating barrel. Two triggers were featured in the arrangement - the first functioned in the normal way (firing the weapon) with the second, forward-most trigger, used to retract the locking pin of the breech. This allowed access to the breech as the barrel could be moved to the right at a 90-degree angle for the purposes of reloading the weapon. The carbine used the Maynard mechanical priming system adopted by other firearms of the period which gave the operator a tactical advantage when reloading.
The gun was trialed before the U.S. military in December of 1854 and proved sufficient enough to warrant an order coming in May of 1855 for 200 carbines. Evaluations continued into 1858 but arising deficiencies, an better competing types now available, soon led to waning interest in the design. This led Greene to market the carbine to foreign parties and secured the British government contract for 2,000 units (as Britain was faced with its own war in Crimea at the time). The guns were not exported until the end of the war, however, which defeated their original purpose. Deliveries occurred in 1858 but the stock languished in storage for some time as the British attempted to find a more suitable cartridge to use in them.
It is believed that some of this number made their way back to the United States during the Civil War and a few were noted to be used in the conflict - most likely acquired through middlemen companies selling to the American government and possible as part of mixed orders.
British versions were identified by their 18" barrel lengths and repositioned slings which were mounted halfway down the stock underside. Original American patterns used a 22" barrel length.