Looks like a real mix up in the records.
The 17th Alabama Infantry Battalion, Sharpshooters, was originally organized with two companies by the assignment of detachments from the 19th and 39th Infantry Regiments in June 1862. The unit disappeared from the records in August 1864, with the members possibly returned to their original commands. The unit was involved in the battles at Murfreesboro, Chickamauga, Chattanooga, in the Atlanta Campaign, and New Hope Church, and in the siege operations at Chattanooga and Atlanta.
Field officers: Lt. Col. Benjamin Cunningham Yancey; and [Acting] Adj. James H. Foster
Captains, and counties from which the companies came:
Co. "A", organized, June 1862, by transfers from various companies of the 19th AL: James F. Nabers
Co. "B", organized, 21 June 1862, by transfers from the 39th AL: William J. Burton
http://history-sites.com/%7Ekjones/gardner.html#17th-Inf-Bn