The Spencer Repeating Rifle has been credited with the Union win at the Battle of Gettysburg. Captain O. E. Hunt, an instructor in the United States Military Academy in his report in 1865 states that “… with the use of the Spencer Rifle by General (John) Geary’s troops at Gettysburg, a whole division of Ewells corps was repulsed by inferior numbers…the head of the column (Confederate) as it was pushed on by those behind appeared to melt away or sink into the Earth, for though continually moving, it got no nearer.”
The invention by Christopher Minor Spence was mostly abundantly rendered as a carbine version, but a $45 magazine fed single shot rifle that could reload in a fraction of the time it took a ball and musket weapon. It also packed a punch in the load in the .56 cal round and it was surprisingly accurate for a carbine.
The truth of the matter is that this rifle almost did not get produced. In fact only a meeting with Lincoln himself produced a contract and by the end of the Civil War the US had produced upwards of 200,000 lever action rifles. Michigan’s Civil War Governor was Austin Blair, and he used his influence to supply the 5th and 6th Michigan regiments with 600 some odd Spencers. Only when Confederate Cavalry attacked Mead’s lines in the flank on July 3rd 1863 did the rifle make its presence known. Most of the Union troops behind breastworks at Gettysburg were armed with Sharps, Burnsides, Merrills, Ballards, and Maynards.
These guns required two actions: one had to pull back the hammer, then load with a lever and then fire.
Source: History Channel, Wiki