Roster of Confederate Soldiers, 1861-1865 shows:

McDuffie, John TN 40th Inf. Co.C

TENNESSEE 40TH INFANTRY REGIMENT
ORGANIZED: at Memphis in October 1861 and thus mistakenly assumed by the War Department to be a Tennessee unit. Designated as the 5th Confederate on February 25, 1862. Surrendered at Island #10 on April 8, 1862. Paroled at Vicksburg, Mississippi, in September 1862. Disbanded in September 1862. Companies "A","E","H" and "K" became companies "B", "I", "A", and "K", 54th Alabama Infantry Regiment, respectively. Company "B" became Company "K", 8th Kentucky Infantry Regiment. Company "C" [actually a Florida Company] became 2nd Company "E", 42nd Infantry Regiment. Companies "D", "F", "G", and "I" became companies "B", "E", "D" and "A", 15th [Johnson's] Arkansaw Infantry Regiment, respectively.

TENNESSEE 42ND INFANTRY REGIMENT
Paroled at Vicksburg in Sept 1862; declared exchanged Nov 10, 1862. Underwent many field consolidations to the end of the war. Designated as the 4th Infantry Regiment Consolidated at Smithfield, North Carolina, On April 9, 1865 for the purpose of surrender.

Suggest you contact
Tennessee State Library and Archives
403 7th Avenue, North
Nashville, Tennessee 37243-0312
615-741-2764

You should also get his service record, either through
National Archives and Records Administration
8th & PA Ave NW
Washington, DC 20408
202-501-5400
you will need NATF Form 80
Cost is about $17 with 90-120 days wait

or use the one I use
soldiersearch@ec.rr.com
http://www.broadfootpublishing.com
bpc@ec.rr.com
910-686-9591 [ask for Page and tell her Johnny Reb sent you]
cost is $25 but turn around time is usually less than 1 week