You may also want to read this book, by a forum member and although I haven't read it, I've read a number of excerpts from it:
Sharpshooters (1750-1900): The Men, Their Guns, Their Story by Gary Yee
I posted a List of Sniper and related books that we had in our library a few years ago that I have to add some new purchases to:
http://www.thehighroad.org/showthread.php?t=463698&highlight=list+of+sniper+books
Since the house fire five years ago, I've been able to replace nearly seventy percent of the titles and of course added new titles as well.
Excepting a very few, the Civil War snipers weren't 800 to 1,000 yd shooters and any shooting at that distance was plunging fire for harassment (of artillery) not accuracy...Berdan's Sharpshooters used the Sharps Model 1859 rifle (after rejecting the Colt Revolving Rifle) and the rifle lacked the accuracy, energy/velocity and the sights would hide the target totally at those distances...They had very few scopes available with all the industrial might of the Union behind them but that's because there were very few glass makers capable of creating those instruments...In actuality the South had more scoped rifles then the North did prior to the onset of war and they were mounted of very heavy barrelled, under hammer, "chunk guns".
What you're forgetting is that between the Civil War and the Spanish American War there was a major development in firearm technology--no, not the Mauser bolt action but that's way up there in importance but smokeless powder so all the tactics had to be altered to deal with the much greater range and of course, rate of fire.
Even during WW1, as in the Civil War, most of the snipers were using open sights...Why, you ask, because the telescopic sights available were horrendously expensive, of very poor quality and extremely fragile just like in the Civil War...Sure they were used, in the later years as technology improved but at the onset, the British Expeditionary Force was using all German made glass that they had prior to the war breaking out as British Optics weren't geared for scope production.
Also, comparing the tactics between Civil War to WW1 and then to WW2 necessitated a different approach...Open field massed troops vs. trench warfare of as close as 50 yds vs open field again but not massed...It was the Russians who first incorporated a semi auto rifle with scope for snipers, actual sniper platoons that were attached to a division as opposed to a single sniper attached to a company and also female snipers...The Germans (Nazis) were the ones to first start actual sniper training schools that was dedicated to trade craft and marksmanship and when Russia and them were still friends, Russia sent select marksmen to train there.
During the World Wars as also between the Korean and Vietnamese Police Actions sniping, as a trade craft, may have been shelved but marksmanship wasn't as all the branches competed regularly...The first guns that they used in Vietnam were taken from the National Match Shooting Teams and scoped--Winchester Model 70s in .30/06 but there wasn't any cadre of snipers just marksmen, who were the first instructors firstly for the Marine and later the Army sniper schools in Vietnam.
It wasn't until well after Vietnam that a US sniper designation was started with dedicated training schools and it wasn't until after Desert Storm that a super critique was incorporated with psychological testing and with actual company attachments came about...Now of course they've expanded the concept with Designated Marksmen using semi autos.
Pegler is a damn good writer and I've enjoyed all his books:
Osprey Elite 068: The Military Sniper Since 1914 -- Great series of books
Osprey General History 022: Out of Nowhere: A history of the military sniper, from the Sharpshooter to Afghanistan
Osprey Warrior 004: U.S. Cavalryman 1865-1890
Osprey Warrior 016: British Tommy 1914-18
Osprey Warrior 031: Union Infantryman 1861-65
To Live and Die in the West: The American Indian Wars
Firearms in the American West 1700-1900
Sniping in the Great War --
Absolute must read
Sniper Anthology: Snipers of the Second World War -- Coming Nov 2011
Osprey Weapons: Sniper Rifles: From the 19th to the 21st Century
Osprey Weapons: The Lee-Enfield Rifle -- Very well researched
Osprey Weapons: The Thompson Submachine Gun: From Prohibition Chicago to World War II--Haven't bought it yet but it's on the list.