One source referencing how Terry's Rangers were armed is "Claiborne'History of Terry's Texas Rangers (Part 1)" available on the internet "www.terrystexasrangers.org/newsclippings/ne-birmingham-times/1891_00_00.html"
Claiborne states at the opening charge at the Battle of Rowlett's Station (Woodsonville) Dec.1861 "In a moment more, the Ranger was in his element, he having first discharged his double barrel gun among the enemy [as] soon as he got within twenty to thirty yards. Now they are together, The federals have empty guns and the Ranger his two six-shooting pistols, of which he is a perfect master, and the carnage is dreadful and frightful to behold..."
The description is Capt. Ferrell's charge on the left side of the railway.
Further citation of the armament comes from the same article but is quoting the Chaplin of the 15th Ohio Regiment USA: "... (the Rangers) came within ten feet of the muzzles of the guns or our men. Here they (the Rangers) halted and did not stir or budge one inch until each one of their number had fired fourteen shots, being armed with a pair of revolvers and double barrel shotgun apiece...."