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.
| 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
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"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
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"Mystery of the South Seas. Argentine cruisers Almirante Brown and Veinticinco de Mayo"
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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