Up to July of 1863, only rifles had been built. Most of these had been issued to _cavalry and mounted infantry_. As popular as they were, there was an almost immediate call for carbines. The rifles were too heavy and cumbersome for mounted service. Also, not being equipped with a sling ring, there was a very great danger of loosing the weapon if it was dropped, leaving the unfortu nate trooper unarmed.
Spencer had originally built rifles because the Army refused to raise state cavalry regiments early in the war. The belief in Washington was that the conflict would be over in less than the two years required to properly train a cavalry regiment. Now that Federal volunteer cavalry was becoming effective (strangely enough, two years into the war), the need for first class carbines was great.
In June of 1863, as the last of the Army's 7500 rifles were being delivered, the Spencer company approached the War Department with a proposal to deliver carbines. This was quickly accepted and led to a contract for 11,000 of the short guns. Initial delivery was to begin in August and be complete before the end of the year. The price was set at $25.
As usual, deliveries were late, but much less than before. The first carbines were accepted on October 3rd, 1863. Seven thousand were turned over to the Army by year's end. This time the order was not reduced for late deliveries. The worth of the repeaters was finally being appreciated. Before the contract was completed, the quantity was increased to 34,500.15
The Spencer Repeating Rifle Company was finally beginning to thrive. There would be more problems, but the repeating weapon for the average trooper was finally beginning to be appreciated. The American Civil War was making the transition from the wars of the past to the wars of the future. In part this was due to the efforts of a single Yankee mechanical genius.
In all, during the War for Southern Independence, the Spencer company delivered 12,472 rifles, including 1003 for the Navy as well as Wilder's and the Massachusetts guns, both of which were diverted to the Federal Ordinance Department. The number of M1860 carbines made by Spencer eventually totaled 45,785. An additional 30,502 M1865 carbines were made by the Burnside company, but deliveries started just at the end of the war, so none were actually in service before the Army of Northern Virginia surrendered. There were a few thousand civilian sales in addition to government deliveries. Many troops took advantage of a government offer and purchased their Spencers when they mustered out at the close of the war
12,500 total rifles is not alot. And still most of those were sent to cav and mounted inf.
Only references to the sharps rifle I can find is as strictly a sharpshooters weapon. Any other info would be welcome.

But we have Sharpshooter units already in the game. A case could be made for having Union SS units have a late war bonus like US cav.
Nial