Alma mounted her four Modèle 1864 breech-loading guns in the central battery on the battery deck. The other two 194 mm guns were mounted in barbettes on the upper deck, sponsoned out over the sides of the ship. The four guns were also mounted on the upper deck. She later exchanged her 194 mm guns for newer Modèle 1870 guns.de Balincourt and Vincent-Bréchignac, p. 28 The armor-piercing shell of the 20-caliber Mle 1870 gun weighed while the gun itself weighed . The gun fired its shell at a muzzle velocity of and was credited with the ability to penetrate a nominal of wrought iron armour at the muzzle. The guns could fire both solid shot and explosive shells.Brassey, p. 477
