Bullseye! Brown's Battalion turns out to be the 15th Battalion MS Sharpshooters, which was actually in the general vicinity of Columbus, MS, in June 1862!

The SS were a two-company battalion, so a temporarily-added, third company would, indeed, have been styled "Co. C.," as were the "Kemper Fencibles"!

Mystery solved! And, now, I can proudly say that my Confederate ancestor/hero, Henry James Gully (among 14 CS grandfathers), served in four units during our Second War of Independence: Co. I (Kemper Blues), 1st (Patton's) MS Infantry (MS "Army of 10,000"); Co. K (Kemper Fencibles), 43rd MS Infantry; Co. C (Kemper Fencibles), 15th Battalion MS Sharpshooters (aka "Brown's Battalion"); and, Co. K, 14th MS Infantry (Consolidated) [at war's end].

Thanks, again, Rick! And I'm glad I'm not the only one who couldn't find "Brown's Battalion" in the OR, even though it is clearly in the OR! -- Jim Huffman, proud Confederate descendant