6" BL Field Guns recovered from the deep.

 

Some time in the 1990s, I took this picture of two field guns dredged-up in Gibraltar from near Ragged Staff and subsequently displayed on Gun Wharf.

A little research determined that these were 6 inch BL Guns, produced around the turn of the century and widely used in the 1^st World War. But first, a little history:

 The first breech loading artillery pieces were adopted by the British in 1859, having been developed by Armstrong over the previous five years. The historic problem had been successfully sealing of the breech to prevent escape of gas. Armstrong achieved this with a soft metal ring let into the breech closure. This was adequate until ironclad ships were introduced and larger guns were required to defeat their armour; Armstrong’s breech closure was not strong enough to withstand larger charges of powder. So in 1865 the British adopted the rifled muzzle loaders (RML) of which we have numerous examples around us, here on the Rock.

                                                 

        

                                                         10 inch 18 ton RML at Southport Gate

 

Throughout the 1870s RMLs became the backbone of coastal defence and naval gunnery, but as barrels became longer (to extract the most bang from a charge and increase muzzle velocity) muzzle loading became more onerous. This led to renewed interest in breech loading, which was about to make a comeback. The device which was to make BL guns easy to handle and solve the gas seal problem was the Welin Screw Breech Block, pictured here.

 

     

 The breech block was slightly coned and the screw was interrupted, allowing it to be swung open after only a 45 degree turn and it incorporated a novel seal. A rod through the centre of the block had a mushroom head and when the charge was detonated, the mushroom was driven back against a circular seal which effectively closed the bore so no gas escaped. Credit where credit’s due; Vickers obtained the patent for the interrupted screw block from Swedish engineer Axel Welin and the mushroom seal from Frenchman, Charles de Bange.   

 Production of the 6” BL guns at Elswick (Armstrong) and at the Royal Gun Factory commenced in the 1880s and was largely directed toward the Navy but gained export sales to Japan and America. Early UK sales found their way on board HM ships and then eventually to coastal gunnery emplacements; which is how we came to have a number installed in Gibraltar. One of the first being at O’Hara’s in 1890.  This gun was fitted to a Vavasseur central pivot mounting, (which absorbed the gun’s recoil on an inclined slide; similar to RML slides). It was probably a Mk III and would serve for a decade before replacement in 1901 with a 9.2 inch.

 

        

 Of the eight 6” BL batteries on the Rock, only Devil’s Gap Battery, completed in 1902, remains intact. These were later Mk VII guns, first produced in 1898, mounted on what was to become the standard Central Pivot pedestal mounts. The most significant change was that recoil was absorbed by an hydraulic cylinder in which the fluid was forced through a small hole in the piston, after which a set of run-out springs returned the barrel to the firing position. Importantly the recoil was backwards not backwards-and-upwards as with earlier marks, making the gun easier to serve.

           

                                                    Devil’s Gap Battery 6” Mk VII BL gun.

                                                    Devil's Gap Battery currently being restored by volunteers.

 The 6” Mk VII BL gun was more widely distributed from 1899, remaining in service until about 1956. Eight hundred and ninety eight were manufactured and it was widely deployed around the British Empire for Coast Defence.  The effective range of the 6” Mk VII BL was about 14,000 yards.

 So far, we have considered naval and fixed emplacement guns but the picture taken by me in the 1990s shows wheeled guns; so how did that come about?

 In February 1900, during the 2nd Boer War in South Africa, a 6” BL gun was brought on shore from HMS Terrible, in Natal, at the request of General Buller to assist him in the relief of the Siege of Ladysmith. The dismounted gun was mounted on an improvised field carriage by Captain (later Admiral) Percy Scott and transported by rail to Colenso. There it was manned by Royal Navy gunners, firing from ‘Gun Hill’ they knocked out a Boer gun at 16,500 yards.

 The improvised carriage was a success, though its construction limited the elevation that could be achieved. This unusual deployment might have remained a one-off except that the 1^st World War appeared on the horizon and the military had to re-evaluate all available weapons. The field version of the 6” BL gun was to prove an invaluable artillery piece. As the war commenced many engineering establishments turned to armaments production; Swindon railway works was one of the sites producing field guns.

      

     

                              A newly completed 6” BL gun awaiting despatch from Swindon in 1916.

 

The BEF embarked for France equipped with the Mk VII version on Scott carriages which were used on many battlefields including the Somme (in July 1916). But there were limitations to its performance. The carriage was low and did not allow for much elevation, which limited the maximum range. Additionally, the equipment was very heavy, which limited mobility. A better long range gun was needed and in October 1916, Vickers Limited came up with the solution. They reduced the barrel length from 45 to 35 calibres and mated the gun to the carriage of the 8" Howitzer Mark VI, and at a stroke the range increased to 17,400 yards and the weight decreased by half. The new equipment was officially designated BL 6" Gun Mk XIX on Travelling Carriage Mk VIIa; it was lighter, more mobile and had much greater range.

      

 

                                                                                           Gunners’ view.

 

Moving these heavy guns (the gun alone weighed 10 tons) in winter conditions was difficult and led to the introduction of girdles to prevent the wheels sinking in the mud. The all-up weight including the carriage was 22 tons.

 

 Equally, the shells each weighing 100lbs (45kg) and the cordite propellant charges, both the 23lb (10.5kg) light and 28lb (12.78kg) heavy, were laborious to move in quantity.

 

                       

     

                                     BL 6” Mk XIX gun of the 484^th Siege Battery Royal Garrison Artillery

 

  

                               A promotional postcard of the war in France destined for home consumption.

 

Over 300 Mk XIXs were built during World War 1 and the gun served in all theatres, with 108 in service on the Western Front at the end of the war, but it did not completely replace the Mk VII gun until the end of the war.

We now know a little more about these guns but two mysteries remain. How did these two guns come to be in Gibraltar in the first place... and how did they end up submerged in the harbour? 

To an artilleryman, his guns are his Regimental Colours and therefore most highly regarded, so allowing this pair to rest at the bottom of the harbour would have been the ultimate disgrace for whoever was responsible.

 

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                                     First published here December 2024.   Paul Hodkinson.