The Development of the High Angle gun

In the early 1880's the Admiralty conducted experiments with deck armour; 2 inch steel plates just kept out nose-hardened shells and 2 inch wrought iron plates easily kept them out. The siting of the new weapons at Portland was first suggested in December 1885 by the Royal Artillery and Royal Engineers Works Committee. The requisite guns were developed from the old 9 inch RML, which had shot indifferently up to about 4,500 yards. In 1884 one was relined with polygroove rifling replacing the original Woolwich grooves and a different twist given to the rifling, and the carriage was adapted to fire at 35 degrees of elevation. A better proportioned projectile was also employed. This was an economical updating of obsolete weapons. Old guns whose bores were eroded were fitted with new tubes incorporating the changes. The cost of this was about £340 per gun, with the mountings coming to £280: if made from new the cost would have been £848. The gun was mounted on its old carriage and platform so modified as to offer 35 degrees of elevation, giving a range of 10,000 yards. On trials at a distance of 10,000 yards the error on range proved to be only 10.2 yards, and the error in direction only 3.4 yards; the time of flight was 48 seconds. It was hoped that the position finding device used in conjunction with the gun could lay down the range to within 20 yards at a range of five miles. By January 1886 the Inspector-General of Fortifications and the Director of Artillery could state that recent experiments with the gun converted into a howitzer had proved that such weapons would be most effective. However, it was a fact of ballistics that high-angle fire and high velocity were incompatible, and as penetration varied as the square of the velocity, the penetrating power of howitzer shells fired at high angles and with comparatively low velocity was small. On the other hand, the flotation power of ships was limited and if the sides were protected by thick armour, the decks could not be protected by heavy armour also. The practicable limit for deck defence at the time seemed to be 3 or 4 inches of steel, considered penetrable by 9-in. or 10-in. shells. However, if the ship was rnoving then the chances of hitting would be much reduced; the lengthy time of flight of the projectile - as seen above, 48 seconds at 10,000 yards - together with all the other variables, clearly vastly increased the difficulty. But then the accuracy of fire of the ships themselves would be enormously decreased by firing on the move, so a great object would still be gained. In November a second Report on the Revision of Armaments of Portland was produced. The provision of a battery of four high angle guns for the Verne Citadel was confirmed, the guns to be the MarkVI 9 inch. This had a maximum elevation of 75 degrees with an all-round traverse of 360 degrees