According to the Kansas Adjutant General, it appears Reynolds was promoted to farrier and then reduced to the rank of private, the reason for the reduction not being given:
http://skyways.lib.ks.us/genweb/archives/statewide/military/civilwar/adjutant/16/d.html

Farrier//Reynolds, Samuel D.//Leavenworth//Jan. 18,'64//Feb. 4,'64//Red. to ranks

Private//Reynolds, Samuel D.//Leavenworth//Jan. 18,'64//Feb. 4,'64//Pro. Farrier; mus. out with reg. Dec. 6, '65