The book Mississippi Confederate Graves Registration by Betty Couch Wiltshire has J. G. Langston listed in the 12th Miss. Also, that he is interred in Warren County, and the dates given match those on his grave marker in Cedar Hill Cemetery, Vicksburg, Warren Co. This is where I got my info on his regiment.

She compiled the grave registrations in the Mississippi archives from film.

But I am open to looking at other regiments.

I checked out the pensions at familysearch.org and mississippi archives -- no luck for j. g. langston