Could be anywhere from 100-multiple thousands of USD depending on exactly what you have
$100-$200, depending on model and condition.
It should be a #11 cap.
Louis Flobert in 1845 was the first to put a ball on the end of a percussion cap and invent the self contained bullet. He went on to produce rifles and pistols that shot this round which is still produced, called now the BB cap.
There are many reproductions made of the Colt cap & ball revolvers, mostly Italian. You must determine if it is a genuine Colt or a reproduction. A local gunsmith can easily tell you if the gun is worth further research.
If it's a 1863 model then it would be a cap and ball model, not cartridge, and it would be about a 31 or 36 caliber. However, if the piece was converted to cartridge then it COULD be a 32 cal. cartridge.
Depending on condition, box, accessories, papers, etc., it can range from 100-500 USD
Depend on who made it and is it an original or Italian copy.
Blue Book of Gun Values is the place to start
As with most of the battles of the Civil War, the artillery used muzzle loading rifled cannon. The infantry soldiers used a muzzle loading percussion cap rifle, with a socket bayonet, firing a .54 caliber minié ball, such as the Springfield. Officers carried a revolver and a sword. Cavalry troopers used a breech loading Sharps carbine, a percussion cap revolver, usually .44 caliber, and a sabre.
The only one matching your description I can find resembles a Sharps carbine, breech loading paper cartridge cap fired rifle. It sold at auction for $1750.00 5 months ago. Similar ones are currently listed on gunbroker.com from $695 to $4700
100-400 USD
Would really need to know the make of the weapon before this can be answered.