I came across the thread on "Globe-sited" rifles and sharpshooters and thought I'd put my $.02 in.

The term refers to the post and globe sight, mounted on the front of the barrel, which has interchangeable inserts for long-range shooting. Someone posted a photo of a modern version. In the CW the term was used generically for any sort of long range target rifles and I doubt that Bass got a chance to get a close look at them. Sharpshooter rifles are often described as "globe sighted" or "long range" or in similar vague terms so we really don't know exactly what they are talking about.

The most common Union sharpshooter rifle was a heavy target rifle that was made for sporting rather than military use. Most had a brass telescope running down the barrel but some did have post and globe sights. Most likely this is what Bass is referring to. I've posted some photos of various sharpshooter rifles on my web site, scroll down for the heavy target rifle.

http://www.cfspress.com/sharpshooters/arms.html

PS> Could I get the cite for Bass's book? I'm always looking for sharpshooter material.