Search for a regimental history book of the outfit, most regt's did so after the war and my g.grandfather's 4th MN Inf. did so in 1892. MN Hist Soc. put out booklets on some of the 11 regiments and they did for the 4th MN.

Gone to National Archives for his military records, if he had a pension, the pension records will give you more and you must specify and pay for each.

Give me his name and Co. and I will look also in my paid for web site ,HDS out of Mass.