Confusion abounds in the Civil War literature when it comes to the detailed discussion of weaponry. While the pistols and long arms of the 1860s comprise only a segment of its coverage, Firearms in American History: A Guide for Writers, Curators, and General Readers [by Charles G. Worman (Westholme, 2007)] should serve as an excellent quick reference guide for Civil War writers.
I centered my own reading on the 1840-1865 period, and was impressed with the author's ability to effectively convey a great deal of detail (technological background, production info., weapon specs, strengths, weaknesses, etc.) in a small amount of space, while at the same time keeping broader trends in focus. Looked for information is also easy to find, a feature critically important for a good reference work. The volume also swarms with clearly reproduced B&W photographs, while sturdy binding and the use of a heavy weight, high gloss paper ensures durability. Firearms in American History is a top notch production overall, and Charles Worman's encyclopedic historical survey will undoubtedly be much referred to during my own inquiries.