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• 7.5"/52 (19 cm) O.T.

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• 7.5"/52 (19 cm) O.T.

These guns were used on the only "Treaty" cruisers ever to serve in a South American Navy. Built by Odero-Terni at La-Foce and Livorno, Italy. These small cruisers were considered to be very successful by the Argentine Navy.

The guns were apparently a modified version of the 7.5"/45 (19 cm) Mark VI gun used on the Hawkins class cruisers. They seem to have been influenced by German designs, as the guns used a horizontally sliding breech mechanism and the propellant was split between a brass case and a silk bag, similar to German weapons. The breech mechanism was a semi-automatic design which closed when the cartridge case rim struck the ejectors.

Designation	7.5"/52 (19 cm) O.T.
Ship Class Used On	Veinticinco de Mayo class
Date Of Design	1927
Date In Service	1931
Gun Weight	N/A
Gun Length oa	N/A
Bore Length	389.0 in (9.880 m)
Rifling Length	N/A
Grooves	N/A
Lands	N/A
Twist	N/A
Chamber Volume	N/A
Rate Of Fire	4.3 rounds per minute was achieved during testing 1

• ^As these guns had a maximum loading angle of +12 degrees and both guns needed to be loaded together, I suspect that the practical rate of fire was about 3 rounds per minute.

Type	Cartridge-Bag
Projectile Types and Weights	SAPC - 198.4 lbs. (90.0 kg) 1a Target - 198.4 lbs. (90.0 kg) 2a
Bursting Charge	SAPC - 13.2 lbs. (6.0 kg)
Projectile Length	N/A
Propellant Charge	N/A
Muzzle Velocity	3,070 fps (936 mps)
Working Pressure	N/A
Approximate Barrel Life	N/A 3a
Ammunition stowage per gun	160 rounds

• ^SAPC shells were officially designated as "SAP" but they had a thin AP cap and a very small ballistic cap, features that are more characteristic of a SAPC type.
• ^The Target projectile was officially designated as "AP" but it did not have a burster and was used only for practice shots.
• ^At such a high muzzle velocity, barrel life was probably quite short.

Range of SAPC Shell with MV of 3,070 fps (936 mps)

Elevation	Distance
45 degrees	29,860 yards (27,300 m)

Designation	Twin Mounts 1b Veinticinco de Mayo (3): N/A
Weight	N/A
Elevation	-7 / +45 degrees
Elevation Rate	N/A
Train	+150 / -150 degrees
Train Rate	N/A
Gun recoil	N/A
Loading Angle	-7 to +12 degrees

• ^In appearance and in many details these mountings were similar in design to Italian 203 mm/53 Model 1927 twin mountings. Like those mountings, the two guns in these turrets were in a single slide.
• Gun axes were 31.9 in (81 cm) apart.

"Naval Weapons of World War Two" by John Campbell "Cruisers of World War Two" by M.J. Whitley --- "Catálogo de Granadas y Proyectiles" by Departamento Munición y Química de Guerra, 1958, p. 21 "Artillería" by División Náutica y Armas Navales, 1952, p. 28 --- "Mystery of the South Seas. Argentine cruisers Almirante Brown and Veinticinco de Mayo" --- Special help by Alec Whalen and Iván Dubaniewicz

30 November 2007 - Benchmark 27 December 2021 - Converted to HTML 5 format, added SAPC details 10 December 2022 - Added details on gun construction, ammunition and mountings

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