R.D, from what I have read they carried Spencer carbines, at least in 1864. I have a book out about the 8th Missouri and their roll in military operations in Arkansas in 1864-65.
http://www.amazon.com/Arkansas-Late-Civil-War-Sesquicentennial/dp/1626191077/ref=sr_1_1?s=books&ie=UTF8&qid=1389477470&sr=1-1&keywords=arkansas+late+in+the+civil+war