Here's one small clue, your next best bet would be to persuse his service record file. These may be procured through the service noted above.

George Martin

James Hearns

Residence was not listed; 18 years old.
Enlisted on 8/9/1862 as a Private.
On 9/15/1862 he mustered into "C" Co. OH 103rd Infantry
(date and method of discharge not given)
Sources used by Historical Data Systems, Inc.:
- Official Roster of the Soldiers of the State of Ohio

See also:

103rd Ohio, "Journal-History of the Hundred and Third Ohio Volunteer Infantry," by Phillip C. Hayes. Originally published in 1872 at Bryan, Ohio, this book may be difficult to locate.

103rd Ohio, "Personal Reminiscences and Experiences by Members of the 103rd Ohio Volunteer Infantry. Campaign Life in the Union Army from 1862 to 1865," by Stephen B. Oates. 440 pages. Roster. Costs around $ 25.00.
http://www.mosocco.com/ohio.html

http://www.ohiocivilwar.com/cw103.html
http://www.103ovi.org/
http://sunsite.utk.edu/civil-war/unit3.html