Have you tried the Compiled Service Records for the 27th Texas Cavalry at the national Archives? These are also online at Fold3.com and their record of events in the first part of these CSRs list all of their engagements typically. The Supplement to the Official Records also has this transcribed. I would also check with the Ed Bearss Vicksburg trilogy and any records in the Texas State Archives for this unit.

Greg Biggs