There were many guns that had permeated the battlefields of the American Civil War (1861-1865). Muskets and rifles and those designs in-between were encountered throughout the various campaigns. War also meant good business for gunmakers and this thrust a myriad of manufacturers and designs into the fold as any and all small arms were required for the years-long war effort that lay ahead. Mahlon J. Gallager of South Carolina designed his "Gallager Carbine" and was granted a patent prior to the war on July 17th, 1860. The carbine was eventually purchased in some number by the Union Army and went on to be used by U.S. Army regiments of both Ohio and Tennessee. Manufacture was handled out of Philadelphia under the Richardson and Overman brand label and this was sustained for the duration of the conflict - which ended in 1865 - with about 18,000 examples completed (17,782 in sources).
A robust weapon, it was not entirely well-liked by Union troops that used it as the cartridge cases it fired had a tendency to "stick" in the action once spent (there was no ejector mechanism fitted) primarily due to heat expansion occurring at the frontal metal sections and requiring considerable effort to remove the case. However they did prove popular as post-war civilian market weapons.
In its original form, the carbine fired a .50 cartridged bullet through a single-shot action. Barrel length measured 22.25 inches which made it a manageable weapon when compared to the true long guns of the war - a trooper on horseback could wield it and scouts favored shorter arms in the brush. A single-piece wooden stock, incorporating the butt section, receiver and a short forend, was used. The action was embedded within the mass of the stock in the usual way with the trigger group underslung. The hammer sat along the right side of the weapon and was cocked back when readied, falling on a percussion cap set upon an awaiting nipple by the operator. The stock included a small integrated compartment, a long iron "patchbox". Forward and rear iron sights were fitted over the rifle for ranged work.
Unlike muskets, which were loaded at the muzzle, the Gallager was loaded at the breech. A brass case was used containing both bullet and propellant which gave the carbine a most modern quality and some speed in reloading. The trigger guard acted as a lever to allow the barrel to tilt upwards and provide the needed internal access to the chamber. Once reloaded, the operator simply brought the barrel back to the stock to close the chamber.
In time, the Spencer .56-52 cartridge was adopted for the line and this improved the overall function of the carbine.
Gallager guns existed into the post-war period and full-length rifled models (in .44) as well as shotguns were encountered (through conversions) - all following the basic, proven design.