guns were chosen to compensate for the smaller 381 mm shell as compared to the 406 mm gun originally desired. The 381 mm guns had a maximum elevation of 35 degrees, which allowed them to engage targets out to . The guns fired a armor-piercing (AP) shell at a muzzle velocity of . However, this was reduced to in order to reduce dispersion and increase barrel service life. The semi-armor piercing shells formed the secondary ammunition of the 381mm/50, which had a bursting charge. Although high explosive shells weighing were developed for the 381 mm guns, they never saw service on the Littorio-class. Shell rooms were located below the propellant magazines beneath the gun house in the turret structure. The guns' rate of fire was one shot every 45 seconds. Their ammunition load was 495 AP shells and 171 SAP shells, with 4,320 propellant charges (666 rounds total, or 74 rounds per gun split 55 AP & 19 SAP). The ships' secondary battery consisted of twelve L/55 Ansaldo Model 1934 guns in four triple turrets. Two were placed abreast the No. 2 main battery turret and two on either side of the rear turret. These guns fired a AP shell at a muzzle velocity of . They could elevate to 45 degrees, permitting a maximum range of . They had a rate of fire of slightly better than four rounds a minute. Four L/40 guns were mounted on each ship in order to fire illumination rounds. Able to elevate to 32 degrees, they fired a semi-fixed round out to an effective range of . The ships' anti-aircraft armament was composed of a powerful battery of twelve 90 mm (3.5 in) L/50 guns closely arranged amidships, twenty L/54 guns, and sixteen L/65 guns. The 90 mm guns provided long-range anti-aircraft protection, and were mounted in quadriaxially stabilized single turrets. They had a rate of fire of 12 rounds per minute and had a ceiling of approximately . The 37 mm and 20 mm guns were designed for close-range defense and had effective ranges of and , respectively. Armor The main belt armor of this class was designed and tested to resist 381 mm armor-piercing shells at ranges down to , which was considered the inner edge of optimal combat range. The belt consists of a homogeneous armor outer plate and the cemented armor belt placed behind the outer plate; the 250