Howdy,
You'll find info on the 11/17th Consolidated (Mounted) Inf under Arkansas Infantry units on Ken Jones Confederate pages at www.tarleton.edu/~kjones/confeds.html . Your ancestor is listed as Cormac, no K.
He is listed as Cormack, G. L. in the Civil War Soldiers and Sailors database at www.itd.nps.gov/cwss/ .
Hope this helps,
Bobby