British 12"/25 (30.5 cm) Marks III, IV, V and Vw

British
12"/25 (30.5 cm) Marks III, IV, V and Vw
Updated 19 October 2007

Early breech loaders using black powder for propellant. Replaced the 12"/25 (30.5 cm) Mark II after those guns failed during testing.

Mark III was an Elswick design, Mark IV and V Woolwich designs and Mark Vw a Whitworth design. All were to complicated design of forged steel construction with multiple hoops. All had a screw breech with four interruptions that was hydraulically operated and completely detached from the gun when the breech was open. Six Mark III, four Mark IV, seven Mark V and five Mark Vw were manufactured. Although different in construction, all of these Marks were interchangeable with each other.

Actual bore length was 25.25 calibers.

HMS Collingwood at the 1902 Review
Note the open barbettes

Gun Characteristics .

Designation	12"/25 (30.5 cm) Marks III, IV, V and Vw
Ship Class Used On	Mark III: Colossus Mark IV: Edinburgh Mark V: Hero Mark Vw: Collingwood
Date Of Design	about 1890
Date In Service	1892
Gun Weight	45 tons (46 mt) inc. breech
Gun Length oa	328.5 in (8.344 m)
Bore Length	303 in (7.696 m)
Rifling Length	N/A
Grooves	N/A
Lands	N/A
Twist	N/A
Chamber Volume	N/A
Rate Of Fire	0.3 - 0.5 rounds per minute
Note: At target practice in 1887, HMS Colossus achieved a record by firing four rounds in six minutes.

Ammunition .

Type	Bag
Projectile Types and Weights	AP - 714 lbs. (324 kg)
Bursting Charge	N/A
Projectile Length	N/A
Propellant Charge	295 lbs. (134 kg) P.Br. (Prismatic Brown - cocoa)
Muzzle Velocity	1,914 fps (583 mps)
Working Pressure	N/A
Approximate Barrel Life	N/A
Ammunition stowage per gun	N/A

Range .

Elevation	With 714 lbs. (324 kg) Projectile
Range @ 12.5 degrees	9,400 yards (8,600 m)

Armor Penetration with 714 lbs. (324 kg) Projectile .

Range	Vertical Iron Plate
1,000 yards (9,140 m)	20.6 in (52.3 cm)
Note: Data from "British Battleships: 1850 - 1950."

Mount / Turret Data .

Designation	Twin Turret Colossus (2), Conqueror (1) and Edinburgh (2) Twin Barbette Collingwood (2)
Weight	N/A
Elevation	Marks III, IV and V: 0 / +12.5 degrees Mark Vw: 0 / +13 degrees
Rate of Elevation	N/A
Train (see Note 2)	Colossus: 0 / about 170 degrees Conqueror: -45 / +45 degrees Collingwood: -90 / +90 degrees
Rate of Train	N/A
Gun Recoil	N/A
Loading Angle	about 10 degrees
Notes: 1) The guns on the Colossus class could only be loaded when the turret was trained to 0 degrees. The breech end of the weapons were lowered below the deck level by a hydraulic ram and then the charges were rammed into the breech from a compartment outside of the rotating structure. 2) The Colossus class had their guns in an amidships citadel with the turrets staggered. This allowed them to fire across the beam although it is not clear if blast effects limited their use in such a manner. They could also fire directly ahead but not directly astern. For the Conqueror class, owing to blast effects on the bridge, it was found to be inadvisable to fire these guns abaft the beam, so the arcs of fire were limited to the figures above.

Data from
"British Naval Guns 1880-1945 No 4" article by John Campbell in "Warship Volume V"
"The Big Gun: Battleship Main Armament 1860-1945" by Peter Hodges
"British Battleships: 1850 - 1950" by Oscar Parkes