12 inch/50 Mark XI (305 mm)

Description

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Vehicles equipped with this weapon

• HMS Colossus

General info

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Available ammunition

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		1,000 m	2,500 m	5,000 m	7,500 m	10,000 m	15,000 m
Mark IIa HE	HE	72	72	72	72	72	72
Mark VIa APC	APC	525	466	382	316	264	198
Mark VIIa SAPCBC	SAPCBC	282	250	205	169	141	105

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay (s)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (kg)	Ricochet
							0%	50%	100%
Mark IIa HE	HE	869	386	0	0.1	53.13	79°	80°	81°
Mark VIa APC	APC	869	389.8	0.025	17	13.64	48°	63°	71°
Mark VIIa SAPCBC	SAPCBC	869	386	0.035	17	36.3	48°	63°	71°

Comparison with analogues

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Usage in battles

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Pros and cons

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History

The launch of HMS Dreadnought in 1906 changed battleship construction when it was introduced. Overnight, the entire fleet of battleships in navies across the globe was obsolete thanks to the introduction of a new all-big-gun design instead of a large secondary battery. What followed the launch of this ship was a global arms race as the major navies around the world began building or ordering their own dreadnoughts. The new Liberal Government that took over Parliament, however, was more conservative in its warship construction. After the launch of the Bellerophon class, capital ship construction was put on hiatus while the British attempted to negotiate a limit to the calibre of naval cannons at the 1907 Hague Convention. When Germany refused to agree to such restrictions, however, Britain rejoined the arms race and approved the construction of the Saint Vincent-class dreadnoughts on June 12th, 1907. The Royal Navy was always looking to improve the firepower of their new ships by taking advantage of newer technological innovations to improve the range and destructive power of their guns. As such the 12-inch 50-calibre Mark XI was created as an improved version of the Mark X guns used on prior ships with a barrel that was five calibres longer and a larger propellant charge. It also replaced the screw collar on the Mark X with a breech ring.

Originally mounted on the Saint Vincent class, they were soon mounted on HMS Neptune which replaced the single forward turret, two rear turrets, and two wing turret configuration found HMS Dreadnought with a staggered "en echelon" gun arrangement that theoretically allowed for all the guns to fire in a broadside such as with Delaware-class dreadnoughts in the United States Navy with their centerline gun arrangement, but in practice, this was only done during an emergency as the blast was found to damage the ship's superstructure. Ironically, it was this concern that led to the rejection of the centerline arrangement by the Royal Navy. The Mark XI had other problems also. Despite the higher muzzle velocity being intended to improve accuracy, it was found the guns were wildly inaccurate due to the propellant charges not completely burning before exiting the barrel. This problem led to unpredictable muzzle velocities and a dispersion pattern between two and three acres. The original prototypes tested by Vickers on HMS Vanguard had a long cylindrical chamber and weren't wired up to the muzzle. However, one of the test guns developed a cracked liner after firing the equivalent of 38 full-service rounds due to the tolerances not allowing for shrinkage for parts, and even if it was allowed, the guns would still be unreliable. The Mark XI* was produced to correct the problem with a thin B hoop that overlapped the jacket along with a larger C hoop partially covering it. While interchangeable with the original Mark XI, the XI* was 1 ton heavier. The Mark XII was produced later with wiring all the way up the casing. It was interchangeable with, and the same weight as, the Mark XI and found service on the Colossus-class dreadnoughts built from 1909-1911. The failure to significantly improve left the Royal Navy with the opinion that they had reached the limits of what could be accomplished with 12-inch guns. The Colossus would become the last class to mount this calibre. The Royal Navy would begin designing larger calibre guns to get their desired performance which created the 13.5 inch/45 Mark 5.

Media

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See also

• 305 mm/45 Mark X (305 mm) - Preceding British 12-inch gun.

External links

• [Wikipedia] BL 12-inch Mk XI – XII naval gun
• [NavWeaps] Britain 12"/50 (30.5 cm) Marks XI, XI* and XII