Almirante Brown was equipped with a main battery of eight 8-inch (203 mm) BLR Armstrong guns, all mounted individually in casemates.
Six were in a central battery, and the other two were in the bow and stern.
These breech-loading guns were a new development, which rendered Almirante Brown a significantly more powerful vessel than even those that had been completed a few years earlier.
She also carried six 4.7 in (120 mm) guns, also in single mounts, all on the upper deck.
Four were mounted forward, and two were located aft, on either side of the 8-inch stern-chaser.
Close-range defense against small craft was provided by a pair of 9-pounder guns and a pair of 7-pounder guns.

The ship was protected with compound armor with a steel face manufactured by the German firm Siemens; the use of steel armor was a new development in naval technology, and permitted significant weight savings.
The main armored belt was 9 in (230 mm) thick amidships, and reduced to 7.5 in (190 mm) at the bow and stern.
Below the main belt was a strake of armor that was 6 in (150 mm) thick amidships and 1.5 in (38 mm) on either end of the ship.
The central battery was protected by 8 in of armor plate in the lower strake, and 6 in of armor in the upper strake.
Atop the central battery, the armored deck was .625 in (15.9 mm) thick, while the deck fore and aft of the battery was 1.5 in (38 mm) thick.
The conning tower also had 8 in thick sides.
Almirante Brown was equipped with a main battery of eight 8-inch (203 mm) BLR Armstrong guns, all mounted individually in casemates. Six were in a central battery, and the other two were in the bow and stern. These breech-loading guns were a new development, which rendered Almirante Brown a significantly more powerful vessel than even those that had been completed a few years earlier. She also carried six 4.7 in (120 mm) guns, also in single mounts, all on the upper deck. Four were mounted forward, and two were located aft, on either side of the 8-inch stern-chaser. Close-range defense against small craft was provided by a pair of 9-pounder guns and a pair of 7-pounder guns.
The ship was protected with compound armor with a steel face manufactured by the German firm Siemens; the use of steel armor was a new development in naval technology, and permitted significant weight savings. The main armored belt was 9 in (230 mm) thick amidships, and reduced to 7.5 in (190 mm) at the bow and stern. Below the main belt was a strake of armor that was 6 in (150 mm) thick amidships and 1.5 in (38 mm) on either end of the ship. The central battery was protected by 8 in of armor plate in the lower strake, and 6 in of armor in the upper strake. Atop the central battery, the armored deck was .625 in (15.9 mm) thick, while the deck fore and aft of the battery was 1.5 in (38 mm) thick. The conning tower also had 8 in thick sides.
ARA Almirante Brown (1880)