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Tomas Sprinter
The 100-ton gun is extremely big. An amazing accomplishment considering when it was ...Read More
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Rosia Road, Gibraltar
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The location of Nelson’s Anchorage and the 100 ton gun, at Napier of Magdala Battery, has long been regarded as strategically important because of its ability to protect the entrances to both the main commercial harbour and what was the Royal Naval Dockyard in Rosia Bay. It was in this bay that H.M.S. Victory anchored for repairs after the battle of Trafalgar in 1805, before returning the body of Admiral Lord Nelson to England for burial.

Designed and manufactured in Newcastle-upon-Tyne, by Sir W.C. Armstrong in 1870 and nicknamed “The Rockbuster’ – this is the best preserved example of an early ‘Supergun’. Four were originally made and sold to the Italian Navy for mounting on their battleships. The British Government, alarmed that their important Mediterranean bases might be defenceless against long range bombardment from these Weapons, commissioned two guns each for Malta and Gibraltar.

For the era in which they were built, they were amazing state of the art and completely unique, and in fact remain so today. Two of those built still survive in the world today. One still resides in Malta and the other here in Gibraltar, at Napier of Magdala Battery.

For informational purposes, the second gun’s location on Gibraltar was at Victoria Battery, on the site of what is now the Gibraltar Fire Station. Aspects of what was the below-ground infrastructure of that gun position still survives as well and remains in use for training by the Fire Brigade of Gibraltar.

Interesting Fact

The gun which you will see currently at Nelson’s Anchorage (Napier of Magdala Battery) is the one that was originally situated at the Victoria Battery, and it was moved to Napier when the gun itself split during firing. The gun could originally fire a round every four minutes, but Lieutenant Colonel Ogilvie’s detachment reduced this time to two and a half minutes, which possibly contributed to the splitting of the original barrel.

The 100 Ton Gun battery at Nelson’s Anchorage was constructed here between 23rd December 1878 and 31st March 1884 on the site of the old 2nd and 3rd Rosia Batteries at a cost of £35,717.00. Named after the governor, Lord Napier of Magdala, it remains a fascinating monument to Victorian artillery and technology.

This gun presented a typical Armstrong appearance, with a steel barrel encased in successive layers of wrought-iron, built up to form an increasingly massive bulk in the breach area. A typical product of the heavy engineering of the Victorian era, it probably represented the Zenith of its kind.

An additional 3.7 inch anti-aircraft gun at the Napier of Magdala Battery in Gibraltar.

The barrel comprised of a toughened steel tube in two parts. Forged and tempered in oil, with a steel ring in halves over the joint, and a series of sixteen wrought-iron coils shrunk on successively.

The 17.72 inch Rifled Muzzle loader, or 100 Ton Gun, has a barrel that is more than 32 feet long and can fire a shot that will range up to 8 miles in distance. Truly an amazing weapon in its time. They were the largest guns of any kind that needed to be loaded through the muzzle, and were so large that it required an hydraulic system powered by steam to carry out the loading and firing operations.

A steam engine pumped water into the bottom of a well, forcing an 85 ton piston up the shaft. It was this weight compressing the water beneath it which provided hydraulic pressure to move the gun. Although the official handbook states that sufficient pressure could be achieved in 35 to 50 minutes – a minimum of 3 hours is more often quoted. What seems today to be a ridiculously long response time was probably adequate for an era in which most ships still had sails.

Each gun required a crew of men to operate it, a crew of about 35 men to be exact, and after the initial head of steam was built up, the crew could fire the gun every four minutes. It took a total of 450 lbs of black prism gunpowder packed into 4 silk cartridges to propel the 2000 lb shell out of the muzzle with a speed of about 1540 ft per second. The cartridges were made of silk because this was almost entirely consumed by the explosion, leaving very little residue in the barrel.

Side closeup of the 100 ton gun at Nelson's Anchorage showing its enormous barrel and incredible craftsmanship.

Like a gigantic cannon, the 100 ton gun was muzzle loaded using hydraulically powered ramrods 45 feet long. Their bristled heads were located in two armour plated loading chambers, situated on either side of the gun. In order to load, the barrel was turned first to one chamber to receive its silk cased charges of black prism gunpowder – and then traversed 180 to the opposite chamber to receive a shell.

The 100 ton gun had a 150 field of fire and was said to be capable of engaging a target up to eight miles away. This would have covered the Bay of Gibraltar – as well as the Spanish mainland towns of San Roque, Los Barrios and Algeciras. However, it is doubtful that this range was ever actually achieved. More conservative estimates put the gun’s maximum range at around five miles and the official record of armament PFG,951 lists the accurate range limit as only 6500 yards.

To impart rotation to the projectiles in flight and thereby increase their accuracy, the inside of the barrel was rifled with 28 twisting grooves. Large copper discs, called gas checks, originally used to stop exploding gases ‘leaking’ past the projectile, also served to impart the spin with the projections to engage in the rifling.

In 1863 Captain William Paliser invented a method of casting shot with the point in an iron mold. This cooled the point more rapidly and produced a brittle, but extremely hard tip – which enabled a shell from the 100 ton gun to penetrate 24.9 inches of wrought iron. A formidable prospect in an age when the best protected vessels only had armour plating 18 inches thick.

Although much about the 100 ton gun would have been familiar to a gunner in Nelson’s Navy – it also contained many revolutionary features. Just one example is that it was fired not by igniting a fuse, but with a platinum wire heated red hot by electricity from a battery.

Photograph of the enormous 100 ton gun located at Nelson's Anchorage at the Napier of Magdala Battery in Gibraltar.

Information necessary to aim the gun was conveyed to a telephonist by range-finders situated higher up the Rock. Since the telephone had only recently been invented in 1876, this post of telephonist must have been one of the first in the British army. However, this use of ‘new’ technology contrasts vividly with the fact that commands within the battery itself were still conveyed by speaking tubes and trumpet calls.

There is a story told about the 100 ton gun that is quite interesting too, which again speaks to us of the technologies of the time. It tells of a visit of the Inspector General in about 1902.

Reportedly they were preparing to fire five rounds at a full charge and on their first try, the tube was all that fired. Further tries on their part as well as misfire drills were attempted but nothing seemed to work.

At the end of the waiting time, which was thirty minutes, the General requested that a volunteer step forward and be put down the gun and fasten a shell extractor to the unfired projectile so that it could be removed.

There was, as one might imagine, a quite long pause prior to a tall thin soldier’s stepping forward and stripping to the waist to be lowered into the gun. He was safely removed from the gun and had completed the task for which he entered it, and it is said that he was, on the spot, promoted to bombardier. Not the most prolific of rewards for having risked life and limb, but certainly one that changed his life!

All in all, the 100 ton gun at Nelson’s Anchorage is certainly well worth a visit, a testament to another, far more violent and uncertain time, when the Rock was unbreachable and the supremacy of the British naval fleets were tested and retested and found to be unwanting.

Opening Hours:
Mon-Sun  09:30 - 17:45
Admission Price:
Adult £3.00
Rosia Road, Gibraltar
+350 54003964


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The 100-ton gun is extremely big. An amazing accomplishment considering when it was built and its ability. Plan on spending about 25 mins or so looking through the small museum and then checking out the gun outside. History on the weapons construction and quite a lot of other interesting information on the wars is on display here. If you are into war history, I guess this would be a must for you ...

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