He soon resumed his old hobby - experiment in rifle work. As early as 1852 Mr Metford had carried out experiments at the long distance of 1,200 yards. About the end of that year he suggested a hollow-based bullet for the Enfield Rifle which was brought to the notice of the Committee on Small Arms in 1853 by Mr Pritchett, and adopted by them. Both at this time and afterwards, he made many experiments on alloys of lead, tin and antimony and on the changes in hardness which take place in them with time.
In 1854 he investigated the disturbance of the barrel by the shock of the explosion, which affects the line of flight of the bullet, a difficulty which has led to much misunderstanding. About this time he designed a form of telescopic sight which he afterwards used a great deal and which was a decided improvement on existing patterns.
He gave much attention to the problem of making an explosive rifle bullet and in 1857 sent in his invention to the Select Committee who found it the best of those offered to them. It was not adopted however until 1863, when it had successfully competed against Colonel Boxer's and General Jacob's shells. It was very cheap and easy to manufacture, the explosive being a mixture of sulphur and chlorate of potash, and the hollow a simple one at the nose of the bullet. The Convention of St Petersburg in 1868 put an end to the use of explosive rifle bullets; but the superior accuracy of the hollow-fronted bullet led to its retention for the Service rifle.
The Volunteer movement of 1859-60 had led to a great revival of interest in rifle work, and at the Wimbledon Meeting of 1862 Mr Metford made the acquaintance of Sir Henry Halford, hence-forward his friend and assistant in his experiments. Together they competed, with rifles specially designed by Mr Metford, for the prizes given by the National Rifle Association in 1864-5 for shooting at 2,000 yards. In both these years Mr Metford's rifles were successful. He now made many experiments to determine the velocity of the bullet at different points in its passage along the barrel and was able to lay down a curve for such a spiral as would give the bullet equal increments of rotation in equal times - the only scientific basis for an increasing spiral. This invention, though it proved to be less important than was at first supposed, formed the subject of a patent. A new form of ballistic pendulum, with double suspension, suggested partly by Mr Froude, was of great help to Mr Metford in his experiments.
Mr Metford's chief distinction in rifle progress however is that he was a pioneer of the substitution of very shallow grooving and a hardened cylindrical bullet expanding into it, for deep grooving and bullets made of soft lead. No one before him had realised that the expansion of a bullet under the blow of the powder was ample and instantaneous and that deep grooving served to accumulate fouling, while soft lead created unnecessary friction. The Whitworth system of polygonal grooving gave far more grip on the bullet than was needed to give it proper spin. Mr Metford found that a bullet could be spun with rifling only 0.0005 inch deep, and that a depth of 0.004 inch was ample for all practical purposes. In 1865 his first match-rifle appeared, having five shallow grooves and shooting a hardened bullet of special design. It immediately achieved prominence in the hands of Sir Henry Halford, and in a very few years Mr Metford's rifles, and those made on the same principles, had left all others far behind.
The Martini action, in combination with the Henry barrel, was adopted in February 1869, by the Small Arms Committee who had before them the work of all the prominent rifle-makers of the day, but not Mr Metford's, and in 1870 he embarked seriously on the production of a breech-loading rifle. He saw that the solid-drawn brass cartridge-case was, for strength and simplicity, far ahead of the compound rolled case adopted for the Service; and that, considering the needs of hot climates and other practical conditions, lubrication of bullet or cartridge was inadmissible. Every detail of the barrel and cartridge received close attention and especially the form of the chamber and of the 'entry' conducting the bullet from the cartridge into the rifling. The adoption of a grooving of segmental form was also found to give great advantages in preventing the accumulation of fouling. It was not long before Mr Metford's first experimental breech-loaders made their appearance and at Wimbledon in 1871 two rifles and a limited supply of home-made ammunition were used. With one of these Sir Henry Halford won the principal prize for military breech-loading rifles - a single prize of £50 - given by HRH the Duke of Cambridge and shot for at 1,000 yards.
In 1872 a match at Wimbledon between teams armed with breech-loaders and muzzle loaders proved that while the latter was certainly still superior, the Henry match breech loader was quite out-classed by the Metford military rifle with match sights attached. By 1877 the rifle and ammunition had passed out of the experimental stage and were made by makers of repute, to whom great credit is due for the good workmanship which was an indispensable condition of the success of the rifle. From that time the record of the military rifle is an unbroken series of triumphs; and in the whole 23 years up to 1894, when military rifles of larger bore than 0.315 were no longer recognised by the National Rifle Association, the Metford rifle only four times failed to win the Duke of Cambridge's prize, while it took a preponderating share of the other prizes. The Martini-Henry, adopted so recently by the Committee on Small Arms as the best breech-loader, soon found its level and after 1882 absolutely disappears from the long-range prize lists for the military breech-loader class. The superiority of the Metford rifle was notably shown in the matches with the military rifle between the Volunteers of Great Britain and the National Guard of the United States in 1882 and 1883 when the American rifles proved to be decidedly inferior to the British, notably at the long ranges, and almost the whole of the British teams used the Metford rifle.
The rapid advance in military small arms abroad, especially as regards quickness of loading, caused the appointment of a Committee to deal with the question of an improved British rifle in February 1883. Mr Metford designed, at the request of the Committee, the detail of the barrel of 0.42 bore for the rifle provisionally issued for trial at the beginning of 1887. But just at this time the question of further reduction of calibre was raised, as a result of Continental experiments, and the outcome was the adoption of the present 0.303 barrel and cartridge for the Service. Mr Metford's unique knowledge enabled him at very short notice to lay down the proper proportions for the grooving, the pitch of the spiral, the shape and dimensions of the 'entry', and the 'clearances' to be given for the cartridge, all so satisfactory that though he himself verified them at much trouble and cost and the Committee also tried them exhaustively, it was found that no modifications could improve them, either as regards accuracy, convenience in use, or ease of manufacture. The 0.303 was first used for black powder, for which his segmental grooving was almost essential, and it was only the rapid destruction of the bore by the smokeless powder afterwards adopted which made it advisable to return to a very obvious form of grooving which had been used by Mr Metford twenty five years earlier. The adoption of the name of Lee-Enfield for the 0.303 magazine rifle with the altered grooving obscures the fact that the shape of the groove was only one of many details connected with the barrel, chamber & cartridge, which are due to Mr Metford's skill. The form of the bullet, for instance, is one which he found to meet with less resistance from the air than any previously invented.
Rifle work was by no means the only subject in which Mr Metford took an active interest. He was something of an astronomer; was an authority on the making of fireworks; and knew much about kite-flying. He studied thoroughly the questions involved in the cutting of precious stones, and at the Exhibition of 1862 showed some jewels beautifully cut by a mechanism of his own invention. He was an interested reader of books on many subjects.
A return, in 1892, of his old illness in an acute form put an end to Mr Metford's active work and after some years of failing health he died on October 14th 1899. Those who knew him will always remember specially his kindness, his deep and genuine nature, his wide sympathies, his extreme accuracy of mind as well as of hand, and his untiring thoroughness of his work.
Mr Metford was elected an Associate of the Institution on 4th March 1856.
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