David,
This is a little off the subject for a Civil War site,but in a few words, I would think that during that time most snipers were using the 03 Springfield and perhaps the Winchester Model 70 or the Remington Model 700. They would all be in 30;06 caliber and would be favored for their accuracy. As for scopes, I can't say. Try googling 'Snipers in Korea' FC