Linda Are you sure that you are dealing with the same person, or another Joel M. McClintock?

It seems that there are 3 Joel M. McClintocks. One a private who enlisted in the 33rd Illinois in Company E from Bureau County in 1861. The second is a 1st Sargeant in company D of the 1st Mississippi Marine Brigade US Infantry. And the third is the Captain of the 57th USCT.

I think that the most likely path is the 1st Sargeant to be promoted to Officer status in the 57th USCT. Now whether it is the Private in the 33rd Illinois Infantry that is transferred and becomes the 1st Sargeant of the 1st Mississippi Marines is another question?