Could this Samuel Park possibly be your man, I would imagine he was a Mechanic/Artificer based on his assignment to the Pistol Factory.
Samuel Park, enlisted as a Private in Company H, Brown's Regiment, Texas Cavalry** March 12, 1863 at Velasco, detailed in Pistol Factory Columbis/Ordnance Deptarment Anderson, Grimes County, Texas March 12, 1863 by order Gen. Magruder/E. K. Smith, paroled July 7, 1865 at Millican, Texas
**Brown's Regiment Texas Cavalry was officially designated the 35th Regiment Texas Cavalry
Samuel H. B. Cundiff, 26 year old Editor born in Hampshire County, Virginia, enrolled as a Captain in Company G, Terrell's Regiment 37th Texas Cavalry (Debray's Brigade, Second Division) April 27, 1863 at Nacogdoches,
The 37th (also known as the 34th and as Terrell's) Regiment Texas Cavalry was first organized as a battalion about March, 1863? and increased to a regiment June 20, 1863. Three companies were transferred to the 35th (Likens') Texas Cavalry and the remainder of the regiment re-organized into ten companies . . . November 25, 1863.