Howdy Longwalker.
I have a two volume set by Douglas C. McChristian called Uniforms, Arms, and Equipment - The U.S. Army on the Western Frontier, 1880-1892. Though I haven't delved into them much at all, they seem pretty informative. I wondered if the same guy did the same thing for the earlier era, and see he has a book called The U.S. Army in the West, 1870–1880: Uniforms, Weapons, and Equipment Illustrated Edition. I don't know anything else about it. Maybe you've seen it?