Argentina
12"/50 (30.5 cm) Bethlehem
Updated 12 July 2008

Used on the only dreadnoughts purchased by Argentina, this gun was probably a copy of the USA 12"/50 (30.5 cm) Mark 7 with an additional breech weight.
WNARG_12-50_Bethlehem_Moreno_pic.jpg

Argentine Moreno off Portsmouth in July 1937
Note rangefinders atop superfiring turrets

WNARG_12-50_Bethlehem_Moreno_front_pic.jpg

Bow turrets of Moreno circa 1930
Note 6"/50 (15.2 cm) gun at right
Photograph courtesy of Georg v. Rauch

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Gun Characteristics
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Designation 12"/50 (30.5 cm) Bethlehem
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 11,863 cu. in. (194.400 liters)
Rate Of Fire 2 - 3 rounds per minute
Note:  Data in this table is taken from the USA 12"/50 (30.5 cm) Mark 7 Mod 1.
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Ammunition
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Type Bag
Projectile Types and Weights
(see Note 1)
AP Mark 15 - 870 lbs. (394.6 kg)
Bursting Charge AP Mark 15 - 25.0 lbs. (11.3 kg) Explosive D
Projectile Length AP Mark 15 - 42.0 in (106.7 cm)
Propellant Charge 337 lbs. (152.9 kg) NC
Muzzle Velocity
(see Note 4)
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
Notes:

1) Data in this table is for the USA AP Mark 15.

2) Bourrelet diameter was 11.977 inches (30.4 cm).

3) The propellant was in four bags.

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Range
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Elevation
With 870 lbs. (394.6 kg) AP Shell
MV = 2,900 fps (884 mps)
Striking Velocity
Angle of Fall
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
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
12.8 degrees
22,000 yards (20,120 m)
1,432 fps (436 mps)
20.5
14.7 degrees
24,000 yards (21,950 m)
1,392 fps (424 mps)
23.9
Note:  Time of flight for AP Shell with MV = 2,900 fps (884 mps)
   4,000 yards (3,660 m):  4.4 seconds
   20,000 yards (18,290 m):  30.1 seconds
   22,000 yards (20,120 m):  34.3 seconds
   24,000 yards (21,950 m):  38.7 seconds
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Armor Penetration with 870 lb. (394.6 kg) AP Shell
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Range
Side Armor
Deck Armor
6,000 yards (5,490 m)
17.4" (442 mm)
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9,000 yards (8,230 m)
14.7" (373 mm)
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12,000 yards (10,920 m)
12.3" (312 mm)
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Note:  This data is from "Elements of US Naval Guns" of 1918.  It is corrected for angle of fall.
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Mount / Turret Data
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Designation Two-gun Turrets
   Rivadavia (6)
Weight 491 tons (498.86 mt)
Elevation -5 / +15 degrees
Elevation Rate N/A
Train
(see Note)
Bow and stern:  about -150 / +150 degrees
Amidships:  100 degree arc
Train Rate N/A
Gun Recoil 38 in (96.5 cm)
Loading Angle Any angle
Note:  Amidships turrets were probably limited to an arc of about 90 degrees in order to minimize blast effects.
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Data from
"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