Served as coxswain on board the U.S.S. Benton during the attack on Great Gulf Bay, 2 May 1863, and Vicksburg, 22 May 1863. Carrying out his duties with coolness and courage, Brownell served gallantly against the enemy as captain of a 9-inch gun in the attacks on Great Gulf and Vicksburg and as a member of the Battery Benton before Vicksburg.