Here is a little info. on the 33rd Texas Cavalry.
CONFEDERATE TEXAS TROOPS
33rd Regiment, Texas Cavalry (Duff's Partisan Rangers)
33rd Cavalry Regiment was organized in April, 1863, by using the 14th (Duff's) Texas Cavalry Battalion as its nucleus. Its members were recruited at San Antonio, Port Lavaca, and Mt. Vernon, and in Kaufman County. This unit served in Gano's and Hardeman's Brigade, Trans-Mississippi Department, and was active along the lower Rio Grande. In April, 1864, it was near Bonham, Texas and contained 23 officers and 307 men. On June 2, 1865, it was included in the surrender. The field officers were Colonel James Duff, Lieutenant Colonel James R. Sweet, and Majors Santos Benavides and John T. Brackenridge.
Battles of the 33rd Texas Cavalry
Point Isabel ( May 30th 1863 )
Near Mier vs. Zapata ( Sept. 2nd 1863 )
Harrisonburg ( March 2nd 1864 )
Palmetto Ranch ( May 12-13, 1865 )
Palmetto was fought after the war had ended so your grandfather may have been in the last land battle of the war!
Your Grandfather may have been in the 14th Texas Cavalry as well as the 33rd Texas Cavalry. What was his name?
I hope this helps,
Gary D. Bray