Armament
The main 190 mm (7.5 inch) guns were designed especially for this class for greater stability (the Trento-class carried 203 mm (8 inch) guns). This could have been a quite powerful gun, but no documents about its characteristics are available in Italian or Argentinian archives. The guns had single mounts to simplify construction, and could fire a 90 kg (200 lb) shell up to 23 km (30,000 yards). Despite this reduction in size and weight, they were still too heavy, so the number of turrets were reduced from four to three. In most respects the resulting vessel was similar in profile to the British York class cruiser.
The secondary armament was also a new design, similar to standard 100–102 mm guns of the time. It consisted of twelve 102 mm (4 inch) DP guns, firing a 13.5 kg (30 lb) shell, all in twin mounts. This was an unusual arrangement for Italian heavy cruisers, which generally carried only four to eight of these weapons. However to counter the additional weight, gun shields were removed, which adversely affected their operability in bad weather conditions.
Unusually, the torpedo tubes were in fixed mounts amidships firing abeam, which caused problems in aiming effectively.
Light anti-aircraft artillery consisted of six Vickers-Terni 40/39 mm guns, all in single mounts, on the aft part of the superstructure. These guns were among the first automatic heavy weapons, firing 100-130 rounds per minute, but were of poor reliability. Though single mounts were simpler and more reliable, they offered poorer fire concentration. The Royal Navy used similar weapons in quad or even octuple mounts. Finally, a catapult launcher for seaplanes was placed over the fore deck.
Armour was within the standard for light rather than heavy cruisers. A 70 mm (2.75 inch) armoured belt was fitted from the first to the last main turret. 60 mm (2.33 in) was used for the command turret. 50 mm (2 in) was used for turrets and barbettes. Only 25 mm (1 inch) was provided for armoured deck and above aft machinery.
Read more about this topic: Veinticinco De Mayo Class Cruiser