Interesting that the letter you quoted mentioned a company meeting, an assembly of volunteers to enlist and organize by the election of officers. Members were paid from that date (Sept. 16, 1861). Company name: "Pike Rangers", Capt. Albert M Collins of Bruceville. The "Pike Rangers" had organized as an AVC company under Capt. Collins, commissions issued to officers on Nov 28, 1860.
The "Pike Rangers" probably assembled at the new Methodist church at Mount Hilliard. Dating from 1856, the church building is located on Bullock County Road 14 between Hook's Crossroads and High Ridge. This portion of Pike County was taken to form Bullock after the war.
The sergeant's name on the census is Joseph F. Barnett, son of James E. Barnett who filed a death claim on Feb 17, 1863. Sgt. Barnett was marked present on the roll for Sept-Oct 1862. It usually took some time to process a claim, so he probably died near the end of the year. Post office for the Barnett family was Mount Hillard; Capt. Collins is recorded on the census at nearby Bruceville.