Michael West, The Thirtieth Battalion Virginia Sharpshooters & Jack L. Dickinson's Diary of a Confederate Sharpshooter: The Life of James Conrad Peters. There's also the O. R. Supplement (Broadfoot Publishing) that breaks a unit down to company and how each company was assigned. You'll have to go to a university library, National Archives, Library of Congress or the Virginia State Library in Richmond to read it.