i got this from
Christopher Spencer’s Horizontal Shot Tower
By Stephen F. Blancard
"Spencer’s first model was believed to have been completed in 1859. His friend R.S. Lawrence, of the firm of Robbins and Lawrence were early contractors of Sharps rifles and carbines. So it is not surprising that some lock parts with interchange with the Sharps. Spencer’s first arms were in .36 and .44 rimfire. These used a smaller frame than the later military models. Spencer obtained his first patent on March 6, 1860. A second patent issued July 29, 1862 contained several improvements to the original design."
"Initially rifles were issued to the cavalry. But the shorter carbine soon proved its superiority for mounted troops. From Jan. 1, 1861 to June 30, 1866 the Federal government purchased 94,196 carbines, 13,171 rifles and more than 58,000,000 cartridges. Spencer was chambered for the No. 56 Spencer rimfire cartridge, also called the .56-56 Spencer. Rifles had a 30” round barrel, full forend retained with three iron bands. About 700 rifles were ordered by the Navy and made to take the sword bayonet. Spencer is though to have actually made about 1,000 on this production run. Probably selling the remaining 300 to the public. All other rifles procured by the government from Spencer were made to take the socket bayonet. The wartime Spencer carbine had a 22” barrel. Approximately 50,000 war model carbines were produced. By the end of the war the Spencer carbine had pretty well established itself as the best arm suited for cavalry use.
After the war, Springfield Armory altered approximately 11,000 war model carbines. The barrels had liners installed to accept the new .50 cal. cartridge. A device know as the “Stabler Cut Off” was added which enabled the gun to be used as a single shot, keeping the magazine in reserve.
In 1865 Spencer came out with a new version appropriately called the Model 1865. This was essentially the same as the war model, except that it was chambered for the new .56-50 cartridge. Production of this model was about 23,000 pieces of which about half are fitted with the Stabler Cut Off. The Model 1865 was also made under contract by the Burnside Rifle Company. Burnside production was approximately 34,000 carbines.
In 1871 Springfield Armory altered 1,108 Burnside made Spencer carbines to infantry rifles. These had their barrels replaced with 32 ½” round barrels chambered for the .56-50 cartridge.
A relatively small number of sporting rifles were made. Some were made on the military action. But others were made using a smaller, scaled down receiver. These were occasionally chambered for the .56-46 Spencer rimfire cartridge."
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Spencer's Repeaters in the Civil War
by A.M.Beck ---> here
http://www.rarewinchesters.com/articles/art_spencercivilwar.shtml
"While these are the two common calibers of Spencer firearms, other chamberings exist. A few very rare and valuable sporting rifles were produced just after the Civil War, mostly from condemned parts. The greater number of these used a bottlenecked 44 caliber cartridge based on the 56-52 case. There are also a very few early prototypes in various small caliber chamberings, particularly 38 and 46 straight."