You will get a lot of replies on the firearms forum. I know this subject has been brought up before try to see if you get lucky with the search engine. The CW was the last war where there was no official one firearm and both sides used various domestic and foreign models. Both sides used captured weapons from the other if they liked the other sides gun better. Arguably the best sniper rifle was the British Whitworth used in small amounts by the CSA it was very expensive and was normally issued one per company when available. There where telescopic scopes but they often broke under field conditions and where delicate and expensive so they where not used as much has they would be in later wars.
Snipers where useful in picking of officers and artillery crews plus they lowered enemy morale. Snipers where nothing new they where used in the Revolutionary War and CSA Gen. Alexander Porter mentions them in the Penninsula Campaign. There must be a few books written about CW snipers.
Leftyhunter