Form 180 can be done over the internet and is free to a relative.you need the person name, birth date, SS no. place of enlistment. If you have a service number it can help.
Though the Archives burned in 1973, they still have some records.It Gives you where he inlisted, and where discharged.
The Government made it mandatory for each state to be responsille for its troops.The State where he inlisted has to have the information.Check with that states archives.They were done on a 5X7 card (now on microfilm) It showed the person name, address where he lived at the time,birth date, next of kin, Muster in date and place muster out date and place rank, along with the division, Inf. and ingagements.It also has medals and ribons received.
These records are not accurate, but I found they retained more information than the Federal Government.