Used on the only dreadnoughts purchased by Argentina, the construction of this Bethlehem gun was probably similar to the USA 12"/50 (30.5 cm) Mark 7.
| Designation | 12"/50 (30.5 cm) Bethlehem
305 mm/50 Bethlehem Marca L Modelos 1/2 1 |
|---|---|
| Ship Class Used On | Rivadavia class |
| Date Of Design | 1910 |
| Date In Service | 1914 |
| Gun Weight | 66 tons (67 mt) |
| Gun Length oa | 607.25 in (15.424 m) |
| Bore Length | 594 in (15.087 m) |
| Rifling Length | 500.925 in (12.724 m) |
| Grooves | (72) 0.075 in deep (1.90 mm) |
| Lands | N/A |
| Twist | Increasing RH 1 in 50 to 1 in 32 |
| Chamber Volume | 14,636 in3 (239.9 dm3) |
| Rate Of Fire | As completed (1914): 1.5 - 2.0 rounds per minute
As modernized (1926): 2.0 - 3.0 rounds per minute |
- ^Modelo 1 was the original design. Modelo 2 had a conical chamber. Modelo 1 was used for all guns on Rivadavia and all but two guns on Moreno, those two being Modelo 2. One Modelo 2 gun was also made for the Argentine gun testing facility.
- Data in this table is taken from the USA 12"/50 (30.5 cm) Mark 7 Mod 1 unless otherwise noted.
| Type | Bag |
|---|---|
| Projectile Types and Weights 1a | AP Mark 15: 870 lbs. (394.6 kg)
Bethlehem SAP: 870 lbs. (394.6 kg) Hadfield AP: 870 lbs. (394.6 kg) 2a |
| Bursting Charge | AP Mark 15: 25.0 lbs. (11.3 kg) Explosive D
Bethlehem SAP: N/A Hadfield APC: 24.3 lbs. (11.0 kg) |
| Projectile Length | AP Mark 15: 42.0 in (106.7 cm)
Others: N/A, but probably about 42.0 in (106.7 cm) |
| Propellant Charge | 337 lbs. (152.9 kg) NC 3a |
| Muzzle Velocity | AP: 2,900 fps (884 mps) |
| Working Pressure | 17.5 tons/in2 (2,760 kg/cm2) |
| Approximate Barrel Life | 200 rounds |
| Ammunition stowage per gun | 100 rounds |
- ^Unless other wise noted, data in this table is for the USA AP Mark 15 which was probably similar to the Bethlehem APC projectiles supplied to Argentina.
- ^In the 1930s, Argentina purchased APC projectiles from the British firm of Hadfield. These projectiles used a delay action fuze and tapin made by Bofors in Sweden.
- ^The propellant was in four bags.
- Bourrelet diameter was 11.977 inches (30.4 cm).
| Elevation | Distance | Striking Velocity | Angle of Fall | Flight Time |
|---|---|---|---|---|
| 0.3 degrees | 1,000 yards (910 m) | 2,802 fps (854 mps) | 0.4 | - |
| 1.4 degrees | 4,000 yards (3,660 m) | 2,521 fps (768 mps) | 1.6 | 4.4 seconds |
| 10.3 degrees | 19,000 yards (17,370 m) | 1,524 fps (465 mps) | 15.7 | - |
| 11.1 degrees | 20,000 yards (18,290 m) | 1,489 fps (454 mps) | 17.3 | 30.1 seconds |
| 12.8 degrees | 22,000 yards (20,120 m) | 1,432 fps (436 mps) | 20.5 | 34.3 seconds |
| 14.7 degrees | 24,000 yards (21,950 m) | 1,392 fps (424 mps) | 23.9 | 38.7 seconds |
The table above is for the USN Mark 15 fired from a USN 12"/50 (30.5 cm) gun. However, official records say that the Argentine guns had a maximum range of 22,750 yards (20,800 m).
| Range | Side Armor | Deck Armor |
|---|---|---|
| 6,000 yards (5,490 m) | 17.4" (442 mm) | --- |
| 9,000 yards (8,230 m) | 14.7" (373 mm) | --- |
| 12,000 yards (10,920 m) | 12.3" (312 mm) | --- |
This data is from "Elements of US Naval Guns" of 1918. It is corrected for angle of fall.
| Designation | Two-gun Turrets
Rivadavia (6) |
|---|---|
| Weight | 491 tons (498.86 mt) |
| Elevation | -5 / +15 degrees |
| Elevation Rate | N/A |
| Train | Bow and stern: about -150 / +150 degrees Amidships: 100 degree arc 1b |
| Train Rate | N/A |
| Gun Recoil | 38 in (96.5 cm) |
| Loading Angle | Any angle |
- ^Amidships turrets were probably limited to an arc of about 90 degrees on either side in order to minimize blast effects.
"Naval Weapons of World War Two" by John Campbell
"US Naval Weapons" and "US Battleships: An Illustrated Design History" both by Norman Friedman
"Battleships: United States Battleships, 1935-1992" by W.H. Garzke, Jr. and R.O. Dulin, Jr.
"Battleships of World War I" by Peter Hore
"Battleships of World War Two: An International Encyclopedia" by M.J. Whitley
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"Range and Ballistic Tables 1935" by U.S. Department of Ordnance and Gunnery
12 July 2008 - Benchmark
23 February 2010 - Added photograph of Moreno gun being installed
17 May 2011 - Added photograph of Rivadavia
03 May 2018 - Converted to HTML 5 format
25 February 2023 - Corrected chamber volume and added information and photograph of Hadfield APC