In the course of his experiments with explosive projectiles, Mr. Metford had found that the hollow-fronted bullet was not less accurate than that of the usual form, and in his later experiments he discovered that, with the Enfield bullet, which had a hollow rear, the accuracy of flight was very considerably increased by the hollow in front. The whole subject of rifle shooting had been brought into fresh prominence by the rise of the Volunteer movement and the formation of the National Rifle Association in 1859-60. Mr. Metford, though his shooting was much handicapped by his health, and he did not shoot very often in competition, found that he could hold his own by using this form of bullet, and indeed had some small advantage over competitors using ammunition of the ordinary pattern. He won, at rifle meetings in the West of England, two first prizes of 100 pounds each, in 1862, and one in 1863. At the Rifle Conference, in January, 1864, he read a paper on the handicapping of men and of weapons, and alluded to the advantage which he considered to be given him by his method of loading. But he felt that, having won enough prizes to repay the cost of his experiments, the best course was to give the secret to the public, and, almost immediately after the close of the Conference, he wrote a letter to the secretary of it, describing the modified bullet on which his success depended; and a full description of it, with diagrams, was published in a pamphlet on Rifling and Rifle Sights," edited by Lord Bury, for the National Rifle Association, in the same year. Mr. Metford, of course, did not patent this bullet, but Sir J. Whitworth, early in 1864, applied for, and obtained, a patent for an exactly similar bullet. When challenged by Mr. Metford, however, he could not prove either originality or priority of invention. The value of this form of bullet may be judged from the fact that when rifle shells were no longer admissible, the form of the bullet was retained unaltered, and continued to be used as the "Metford-Enfield" bullet until the Snider was superseded by the Martini-Henry. In 1865 we find that in the "Volunteer Service Gazette" competition, at Wimbledon, for long Enfield rifles at 800 yards, "any ammunition" was allowed expressly in order to permit the use of Metford bullets, and that the first prize was won by a competitor using them. Advantage was taken by Mr. Metford of the form of this bullet with its considerable hollow in front, to enable the position of the hit on an iron target to be indicated. He filled the hollow with vegetable charcoal, which, as the bullet broke up, made a momentary cloud, easily visible from the firing point. Mr. Metford also pointed out how a similar bullet, made of hardened lead (1 of tin to 15 of lead), would make good shooting at long ranges if fired from a rifle of .577 calibre with a spiral of 1 turn in 3 to 4 feet, and 3 shallow grooves of .01 inch deep.
In 1862 the late Sir Henry Halford came to the front at the Wimbledon meeting as a winner of several important prizes, and Mr. Metford's acquaintance with him, which soon ripened into a lifelong friendship, dated from that time. Henceforward they were associated in all their rifle work, and if Mr. Metford's was the guiding spirit of their partnership, all the zeal, skill, and resources of his friend were ungrudgingly placed at his disposal. They co-operated when in 1864-5 the National Rifle Association gave prizes for a special competition at 2,000 yards with muzzleloading rifles, weighing not more than 15 lbs. Mr. Metford specially made for this competition a rifle of about .5 inch bore with telescopic sight, which gave fair results. It was the only rifle entered in 1865, and in the competition of 1866 the only other competing rifle failed to find the target.
Before this time Mr. Metford had given much consideration to the question of rifling in relation to the nature of the impulse given to the bullet, and he came to the view that the best and most correct way of imparting to the bullet its full rotation would be to cut such a spiral as would give the bullet equal increments of rotation in equal times. Such a spiral would give an equal pressure on the side of the bullet, and the tendency to escape the rifling would be, therefore, represented by the starting pitch of the spiral and not by the final pitch, which starting pitch of spiral would be, in this system, of a much slower rate than in spirals of the usual uniform, rate. In ascertaining the speed of the bullet at different points in passing along the bore, Mr. Metford occupied much time. He had barrels out off to different lengths, but he also calculated the speeds, and finally drew a series of curves ending in different final pitches of spiral, with some of which he finally experimented at the long ranges of 1,000, 1,500, and 2,000 yards. From very early times, variations had been made in the pitch; increasing, and even decreasing, spirals had been used. But they had depended on no rule--merely on the fancy of the maker. Mr. Metford was the first to make the curve of the increasing pitch of the spiral correspond with that of the effective work of the powder. He felt it important to patent his increasing spiral, both to record that it was he who put the principle upon a proper scientific basis, and also to guard himself from unworthy imitations, and for nearly 30 years it was applied to the Metford rifle generally. It does not, however, seem to have been a principal element in the success of the rifle, though it had the incidental advantage of infallibly shearing the paper patch sur rounding the bullet, and so preventing a cause of false shots not unknown in rifles with an even spiral. For the purpose of ascertaining the speed of the bullets projected from different lengths of rifled barrels, it was necessary to design and erect an instrument capable of accurately measuring it. With the help of his ever-ready friend, Mr. Froude, who suggested a method of double suspension, Mr. Metford designed a new form of ballistic pendulum, which was found convenient in use, and very accurate in its results.
Mr. Metford proved, by a very simple experiment, in Feb., 1865, that the expansion of a bullet when fired was effected instantaneously before it acquired any forward motion. Experiments with hardened cylindrical bullets, such as he had used as far back as 1854 (as already mentioned), showed him that the old idea that a lead bullet could not be too soft was entirely erroneous. It was thought that complete and rapid expansion of the bullet into the grooving demanded that it should be of pure lead. This was probably due to the custom of making the grooving of rifles of considerable depth. Mr. Metford soon saw that the great thing was to check the expansion, and to use a hardened bullet giving less friction in the bore. This would allow of the bullet being spun without stripping by a very shallow rifling, and the practical convenience of a cylindrical bullet quickly made itself felt as against the arrangement patented by Sir J. Whitworth, and invented even earlier by Mr. Brunel, wherein was used a polygonal bore with a mechanically fitting bullet. An additional advantage of shallow grooving, and a very important one, was that the trouble caused by the accumulation of fouling, a conspicuous feature of rifles with deep or polygonal grooving, was reduced to a minimum. Delicacy of measurement and extreme accuracy in all essentials was a conspicuous feature of Mr. Metford's work, and he found that grooving of not more than about .004 in. deep would give a proper spin to a bullet of suitable hardness, and that even grooves so shallow as to measure only half of the thousandth of an inch in depth would rotate a bullet. This new system of light rifling with a hardened bullet was very soon adopted by all rifle makers in England and America, excepting Sir J. Whitworth, whose polygonal grooving was very soon completely outclassed.
The first "small bore" rifle made on these principles by Mr. Metford was fired by Sir Henry Halford, who at once made a sensation by winning with it the Cambridge Cup, at the annual meeting of the Cambridge University Long Range Club, in 1865, the competition consisting of 15 shots at 900, 1,000 and 1,100 yards, on each of two consecutive days. This rifle had five shallow grooves, cut concentric with the bore, a form of grooving which, if allowance is made for the difference in size, is the very counterpart of that of the present service arm, the "Lee-Enfield." At the Wimbledon meeting of 1865 there seem to have been only two Metford rifles used, one by Mr. Metford himself and the other by Sir Henry Halford, and they did not take a very prominent place in the prize lists. But in 1866 we find five Metford rifles in the English team for the Elcho Shield and two in the Scottish. The next year six Englishmen used them, and they grew in favour until in 1871 the whole English team shot with them. Meanwhile the Whitworth rifle had disappeared, and the other rifles competing against Mr. Metford's were all based on his principle of hardened bullets and shallow rifling. The pains which he took to perfect each detail by the most careful and exhaustive experiment can hardly be over-rated. The wadding, the bullet, the paper wrapped round the bullet, all were the subject of trial to ascertain the best form, dimensions, and material, always with a special attention to what was simple and practical. And so, year after year, perfection was more and more nearly approached, and Mr. Metford's mind became stored with so much information and experience on his own subject as could be matched by no other man.