ON RIFLE PROJECTILES.
Projectiles used in early guns.
We have learned that out of early Artillery were fired bolts, darts, bombs, stones and (more recently) iron shot. From the harquebus and musket: arrows, darts, quarrels, sprites, iron, and lastly leaden spherical balls. Elliptical iron bullets 1729.Some assert that the idea of lengthened eliptical bullets was enunciated so far back as 1729, and that good results followed their employment, but it is doubtful whether such really did take place.
Leutman.
Leutman, in his “History of St. Petersburgh,” says that “it is very profitable to fire elliptical balls out of rifled arms, particularly when they are made to enter by force.”
Robins 1742.
Robins, in 1742, recommended the use of projectiles of an egg like form, (see [plate 20], fig. 12), they were to be fired with the heavy end in front, to keep the centre of gravity forward.
Beaufoy 1812.
Colonel Beaufoy, in a work called “Scloppetaria,” 1812, remarks that several experiments have been tried with egg-shaped bullets, recommended by Robins. It was found, however, that these bullets were subject to such occasional random ranges, as completely baffled the judgment of the shooters to counteract their irregularity. Their deviations to windward most likely arose from the effect of the wind on the after part, which, as being the lightest of the two, was driven more to leeward, and consequently acted as a rudder to throw the foremost end up to the wind.
Turpin 1770.
In 1770 Messrs. Turpin tried elongated bullets, at La Fiere, and at Metz.
Rifled guns &c., 1776.
We are informed, in the Annual Register for 1776, and also in the Scots Magazine for the same year, that rifled Ordnance were experimented with at Languard Fort, &c., &c., in 1774. Dr. Lind, one of the inventors, states that to remedy the deflection of shot, “One way is to use bullets that are not round but oblong. But in our common guns that are not rifled, I know no way to prevent deflection, except you choose to shoot with a rifled bullet.”
Elongated projectiles 1789.
Elongated Projectiles were tried in the years 2, 6, and 9 of the Revolution, by Mons. Guitton de Moreau. They were proposed by Mons. Bodeau. 1800 and 1815.In 1800 and 1815 the Prussians tried ellipsodical bullets. Colonel Miller, Colonel Carron, Captain Blois, and others, also experimented with the cylindro-conical form.
Captain Norton 1824.
Captain Norton (late 34th Regt.), the original inventor of the application of the percussion principle to shells for small arms, in 1824, completed an elongated rifle shot and shell, the former precisely of the form of the Minié bullet, with projections to fit the grooves of the barrel.
Mr. Greener 1836.
Mr. Greener, in 1836, presented an expanding bullet to the Government for experiment, ([plate 20], fig. 13). It is oval, with a flat end, and with a perforation extending nearly through. A taper plug, with a head like a round-topped button, is also cast of a composition of lead and zinc. The end of the plug being slightly inserted in the perforation, the ball is inserted either end foremost. When the explosion takes place, the plug is driven home into the lead, expanding the outer surface, and thus either filling up the grooves of the rifle, or destroying the windage of the musket. The result was favourable beyond calculation. Of about 120 shots by way of experiment, a man was able to load three times to one of the old musket, and accuracy of range at 350 yards was as three to one.
Mr Greener’s invention rejected.
Mr. Greener’s invention was rejected, and the only notice he received from the Board was, it being “a compound,” rendered it objectionable!!!
Mr. Greener rewarded.
The following extract appears in the Estimates of Army Service for 1857-8. “To William Greener, for the first Public Suggestion of the principle of expansion, commonly called the Minié principle for bullets in 1836, £1,000.”
Wilkinson 1837.
Many experiments were made by Mr. Wilkinson in 1837, with balls precisely similar in shape to the Minié, with a conical hole in them, using a wooden plug; Cork plug 1851.and in 1851 experiments were tried at Woolwich with a soft elastic cork, fitting the aperture in the projectile very closely, the compression of which it was conceived would sufficiently expand the cylindrical part, and make it fit the grooves, &c. In some instances it succeeded perfectly, but in many the cork was driven through the lead.
Gen. Jacobs.
Major-General Jacobs for many years carried on a series of experiments with rifles, and in 1846 submitted a military rifle, with an elongated projectile, for experiments, to the Government at home, and also to that in India. It did not meet with approval in England, and the Company cut the matter short by stating, that what was good enough for the Royal Army was good enough for theirs. There is nothing peculiar in General Jacob’s rifle. He recommends an elongated projectile ([plate 20], fig. 14) solid at the base, cast with four raised flanges to fit into the grooves. General Jacobs states, that the desired initial velocity could not be produced with a projectile made entirely of lead, Form of leaden bullet destroyed.as a slight increase of charge had the effect of destroying the form of the projectile. He also states that the limit of the powers of leaden balls having been attained, it became necessary to find a method of constructing rifle balls, so that the fore part should be capable of sustaining the pressure of large charges of fired gunpowder, without change of form, and retain that shape best adapted for overcoming the resistance of the air, on which all accurate distant practice depends; and at the same time having the part of the ball next the powder sufficiently soft and yielding to spread out under its pressure, so as to fill the barrel and grooves perfectly air tight. Zinc point to bullets.And he professes to have solved the problem, by having the fore part of the bullet cast of zinc, in a separate mould.
Expansion by hollow bore.
Captain Delvigne, who had been experimenting since 1828, proposed the adoption of lengthened bullets, consisting of a cylinder terminated by a cone, which was subsequently replaced by an ogive. He obtained a patent dated 21st June, 1841, “For having hollowed out the base of my cylindro-conical bullet, to obtain its expansion by the effect of the gases produced through the ignition of the powder.”
Hollow in case to throw centre of gravity forward.
The main object of Captain Delvigne in hollowing the base was, to throw the centre of gravity forward; but a Captain Blois, in France, had previously tried this important suggestion. Captain Delvigne states, if the hollow is too deep, the expansion is too great, and the consequent friction enormous; or the gas may pass through the bullet, and leave a hollow cylinder of lead within the barrel. Sometimes the gas will traverse the sides of the bullet, and consequently the projectile is deprived of a proportionate amount of velocity; if too small, the expansion does not take place.
Capt. Minié iron cup.
Captain Minié, an instructor of the School at Vincennes, merely fitted into this hollow an iron cup, hoping to prevent the gas forcing its way through the bullet, and that the iron pressing upon the lead should increase the expansion. ([Plate 20], fig. 7).
A perfect bullet was now supposed to have been discovered, of a cylindro-ogival form, (no part was a true cylinder), having a groove originally intended to fasten on a greased patch, and in some cases the cartridge, but the patch being dispensed with, and the cartridge reversed, Groove suppressed.the groove, supposed to be useless, was suppressed.
Results.
People were then surprised to find that firing lost much of its accuracy, and the groove was replaced; when it was observed that any variation in its shape and in its position, materially affected the practice. Not only variations in the grooves caused great alteration in the accuracy of fire, but any modification bearing on the trunk in rear, or on the fore-ogive, altered the conditions of the firing, so that the groove became lost in the midst of so many other principles, the functions of which were so much unknown. These theoretical considerations served, however, as a point of departure for further investigations.
Tamisier lengthened bullets.
Captain Tamisier had not ceased for several years, concentrating his attention on the subject. He varied the length of the cylindrical part and the angle of the cone, and tried experiments with bullets of 5-in. in length, and obtained considerable range, and great accuracy with them; the recoil however was excessive, and to use such bullets heavier arms, a smaller bore, and other modifications would be necessary.
Centre of gravity formed by blunting tips.
He endeavoured to carry the centre of gravity to the furthest possible point forward, (which Robins suggested 100 years before), but to effect this he was compelled to flatten the fore end of the bullet, which had the disadvantage of increasing the resistance of the air to the movement of projection.
Path rectified by resistance in rear.
He was then led to another plan for rectifying the path of the bullet through each instant of projection, and which was by creating at the posterior end, resistances, which should act in case the axis of the bullet did not coincide with the direction of motion, Many cannelures.and this was carried out by cutting upon the cylindrical part, instead of one, as many circular grooves of ·28 in depth, as that cylindrical, or rather, slightly conical, part could contain. An increased precision in firing was the immediate result. ([Plate 20], fig 15.)
Shape of cannelures.
Feeling his way most carefully, Captain Tamisier then made a great number of experiments in this direction, and perceived that it was important to render the posterior surface of the grooves as sharp as possible, so as to augment the action of the air; for these grooves lose their shape, owing to the lead, from its malleable nature, yielding under the strokes of the ramrod.
Elongated Projectiles, whose Centres of Gravity do not correspond with Centre of Figure.
Elongated projectiles, whose centres of gravity do not exactly coincide with the centre of figure, when they do not turn over, tend to preserve their axis in the primary direction which was imparted to them, in the same manner as an imperfectly feathered arrow flying with little velocity, the point of the moving body being constantly above the trajectory, and its axis making a certain angle ([plate 21], fig 1) with the target to the curve. Action of the air.Therefore the part A.B. of the bullet being exposed to the direct action of the air’s resistance, the atmospherical fluid is compressed on the surface A.B., and rarified upon that of A.C. Hence it will be perceived that the compressed fluid supports the moving body, and prevents its descending as rapidly as would a spherical bullet, which is constructed to meet the same direct resistance from the air. This trajectory will therefore be more elongated than that of the spherical bullet in question.
Remedied by the grooves.
But the resistance of the air, acting upon the groove of the projectile, produces, on the lower part of this groove, an action which tends to bring back its point upon the trajectory, yet with so little force, that often, in its descent, the projectile turns over, and moves breadthways at ranges of 1000 and 1200 yards. The lower side of the projectile, therefore, moving in the compressed air, and the upper in the rarified air, deviation must ensue, for, as the upper part of the bullet moves from left to right, the bottom must move from right to left. Cause of deviation.But the lower resistance to the motion of rotation being produced by the friction of the compressed air, is greater than the upper resistance, which depends on the friction of the rarified air. By combining these two resistances, there results a single force, acting from left to right, which produces what Captain Tamisier termed “derivation,” Remedy.and it was to overcome this derivation that this officer proposed the circular grooves to the bullet, which he considered would act, like the feathers of the arrow, to maintain the moving body in its trajectory.
How to obtain knowledge of the bullet’s rotation.
If, however, we would wish to obtain some idea of the rotatory motion of a bullet in its path through the air, By the arrow.let us consider the action of the arrow, and see how it is constructed, so that the resistance of the air should not act in an unfavourable manner. First, nearly all its weight is concentrated at the point, so that its centre of gravity is close to it. Use of feathers on arrows.At the opposite end feathers are placed, the heaviest of which does not affect the centre of gravity, but gives rise to an amount of resistance in rear of the projectile, and which prevents its ever taking a motion of rotation perpendicular to its longer axis, and keeps it in the direction of its projection. This difficulty which the arrow finds in changing its direction must concur in preventing its descending so rapidly as it would do were it only to obey the law of gravity, and must therefore render its trajectory more uniform.
Similar effects on bullet with grooves.
Let us, however, now come back to the grooves of Mons. Tamisier, and we shall find that they concur in giving to the bullet the two actions of the resistance of the air, which we have demonstrated with respect to the arrow.
Suppose that such a bullet describes the trajectory M, and A.B. be the position of its axis, it will be seen that the lower part of the bullet re-establishes the air compressed, whilst the upper part finds itself in the rarified air. That, consequently the lower parts of the cannelures are submitted to the direct action of the air’s resistance, whilst their upper parts totally escape this action. ([Plate 21], fig. 2). Effect of grooves.The resultant of the air’s resistance evidently tends to bring back the point of the moving body, according to the trajectory; but as this action is produced by the pressure of an elastic fluid, it results that the point B, after having been an instant upon the trajectory, will fall below, in virtue of the velocity acquired; but then the upper grooves finding themselves acted on by the action of the air’s resistance, this action, joined to its weight, will force the point of the projectile upwards, which will descend to come up again, so that the projectile will have throughout its flight a vertical swing, which is seen distinctly enough in arrows.
Union of Robins and Tamisier.
Let us connect the suggestion of Robins, with the experiments of Captain Tamisier, to cause the posterior end to act as a rudder to guide the projectile in its true path, as undoubtedly during the descent of a bullet there is a tendency for the centre of gravity to fall first, as the ball of the shuttlecock. In the first Prussian balls, and in those used in the Tige, the centre of gravity being nearer the base, the rear end of these balls have a tendency to fall before the foremost, but this is most undoubtedly counteracted by grooves, while it would be impossible to fire an elongated projectile with its centre of gravity backwards, with any accuracy out of a smooth-bored gun.
Cannelures improved shooting.
Captain Jervis says that these grooves have the effect of improving the accuracy of firing when the bullets are not perfectly homogeneous, is certain, Why none in English bullet.but the British Committee on small arms justly considered that owing to the careful way in which the bullets are made in England by compression, these grooves might be dispensed with.
Variety of forms.
Almost every conceivable form of projectile, internal and external, have been made and experimented upon. Auxiliaries to expansion, various.Auxiliaries to expansion have been used, made of metal, horn, wood, and leather, with plugs, screws, or cups of divers shapes. Cannelures are used, of varying forms, depth and number.
Rotation from smooth bores.
It has even been attempted to construct bullets upon the screw principle, so that the projectile should receive spirality from the action of the air upon its outer or inner surface, when fired out of a smooth bore musket.
General characteristics of modern rifles.
The general characteristics of the European rifles, up to 1850, are a very large calibre, a comparatively light short barrel, with a quick twist, i.e., about one turn in three feet, sometimes using a patch, and sometimes not, the bullet circular, and its front part flattened by starting and ramming down.
American alterations.
It appears that the introduction of additional weight in the barrel, reduction in the size of the calibre, the constant use of the patch, a slower twist, generally one turn in 6ft., combined with (what is now known to be a detriment) great length of barrel, are exclusively American.
Picket bullet.
A round ended picket ([plate 20], fig. 16), was occasionally used in some parts of the States, until the invention of Mr. Allen Clarke, of the flat ended picket, which allows a much greater charge of powder, producing greater velocity, and consequently less variation in a side wind.
On the comparative merits of rifles.
A rifle may perform first rate at short ranges, and fail entirely at long, while a rifle which will fire well at extreme ranges can never fail of good shooting at short. In fact certain calibres, &c., &c., &c., perform best at certain distances, Points in a perfect rifle.and in the combinations of a perfect rifle there are certain points to be attended to, or the weapon will be deficient and inferior.
Velocity.
It is desirable to give a bullet as much velocity as it can safely be started with, and the limit is the recoil of the gun, and the liability of the bullets to be upset or destroyed, for as soon as this upsetting takes place, the performance becomes inferior, and the circle of error enlarged.
Degree of twist.
It is clear that a bullet projected with sufficient twist to keep it steady in boisterous and windy weather, must of necessity have more twist than is actually necessary in a still favourable time; hence a rifle for general purposes, should always have too much twist rather than too little.
Weight of bullet.
The weight of the bullet must be proportioned to the distance it is intended to be projected with the greatest accuracy; for it is a law, that with bodies of the same densities, small ones lose their momentum sooner than large ones. It would be madness to use a bullet ninety to the pound at nine hundred yards, merely because it performed first rate at two hundred yards; or a forty to the pound at two hundred yards, because it performed well at nine hundred yards. The reason is that a forty to the pound cannot be projected with as much velocity at two hundred yards, as the ninety to the pound can, because the ninety uses more powder in proportion to the weight of the bullet than the forty does. Again, the heavier bullet performs better than the lighter one at nine hundred yards, simply because the momentum of the light ball is nearly expended at so long a range as nine hundred yards, and its rotatory motion is not enough to keep it in the true line of its flight, whereas a heavy bullet, having from its weight more momentum, preserves for a longer distance the twist and velocity with which it started.
Calibre.
As weight of projectile is a leading element in obtaining accuracy at long ranges, and as the weight cannot be increased beyond a certain limit in small arm ammunition, hence a small bore is an indispensable requisite for a perfect rifle.
In the foregoing brief summary of the most important properties which should be possessed by a first class rifle, we have dealt in generalities, Result of Mr. Whitworth’s experiments.but we shall now record the experience of Mr. Whitworth, who has entered into the most minute details, and has pointed out the harmony which should subsist between the twist, bore, &c., and the projectile, in the combinations of a perfect rifle.
Bore and weight limited.
Premising, that when Mr. Whitworth was solicited by the late honored Lord Hardinge to render the aid of his mechanical genius to the improvement or perfecting a military weapon, he was restricted as to length of barrel, viz., 3 feet 3-in., and weight of bullet, ·530 grains. We shall now proceed and use Mr. Whitworth’s words.
Consideration for curve.
“Having noticed the form (hexagonal) of the interior which provides the best rifling surfaces, the next thing to be considered is the proper curve which rifled barrels ought to possess, in order to give the projectile the necessary degree of rotation.”
Hexagonal form admits of quick turn.
“With the hexagonal barrel, I use much quicker turn and can fire projectiles of any required length, as with the quickest that may be desirable they do not ‘strip.’ I made a short barrel with one turn in the inch (simply to try the effect of an extreme velocity of rotation) and found that I could fire from it mechanically—fitting projectiles made of an alloy of lead and tin, with a charge of 35 grains of powder they penetrated through seven inches of elm planks.”
Degree of spiral fixed.
After many experiments, in order to determine the diameter for the bore and degree of spirality, Mr. Whitworth adds: “For an ordinary military barrel, 39 inches long, Diameter of bore determined.I proposed a ·45-inch bore, with one turn in 20 inches, which is in my opinion the best for this length. The rotation is sufficient with a bullet of the requisite specific gravity, for a range of 2000 yards.” Under these conditions the projectiles on leaving the gun would be about two and a half diameters of the bore in length. “The gun responds to every increase of charge, by firing with lower elevation, from the service charge of 70 grains up to 120 grains; this latter charge is the largest that can be effectively consumed, and the recoil then becomes more than the shoulder can conveniently bear with the weight of the service musket.
Advocates of slow turn.
“The advocates of the slow turn of one in 6 feet 6 inches, consider that a quick turn causes so much friction as to impede the progress of the ball to an injurious and sometimes dangerous degree, and to produce loss of elevation and range; but my experiments show the contrary to be the case. Effects of quick turn.The effect of too quick a turn, as to friction, is felt in the greatest degree when the projectile has attained its highest velocity in the barrel, that is at the muzzle, and is felt in the least degree when the projectile is beginning to move, at the breech. The great strain put upon a gun at the instant of explosion is due, not to the resistance of friction, but to the vis inertiæ of the projectile which has to be overcome. In a long barrel, with an extremely quick turn, the resistance offered to the progress of the projectile is very great at the muzzle, and although moderate charges give good results, the rifle will not respond to increased charges by giving a better elevation. If the barrel be cut shorter, an increase of charge then lowers the elevation.”
Objections to increasing spiral.
“The use of an increasing or varying turn is obviously injurious, for besides altering the shape of the bullet, it causes increased resistance at the muzzle, the very place where relief is wanted.”
Length and spiral increased.
“Finding that all difficulty arising from length of projectiles, is overcome by giving sufficient rotation, and that any weight that may be necessary can be obtained by adding to the length, I adopted for the bullet of the service weight, an increased length, Diameter decreased.and a reduced diameter, Trajectory lowered.and obtained a comparatively low trajectory; less elevation is required, and the path of the projectile lies more nearly in a straight line, making it more likely to hit any object of moderate height within range, and rendering mistakes in judging distances of less moment. The time of flight being shortened, the projectile is very much less deflected by the action of the wind.”
Proper powder for expanding bullets.
“It is most important to observe that with all expanding bullets proper powder must be employed. In many cases this kind of bullet has failed, owing to the use of a slowly igniting powder, Powder for hardened bullets.which is desirable for a hard metal projectile, as it causes less strain upon the piece, but is unsuitable with a soft metal expanding projectile, for which a quickly igniting powder is absolutely requisite to insure a complete expansion, which will fill the bore. Consequences of imperfect expansion.Unless this is done the gases rush past the bullet between it and the barrel, the latter becomes foul, the bullet is distorted, and the shooting must be bad. Advantages of hexagonal form.If the projectiles used be made of the same hexagonal shape externally as the bore of the barrel internally, that is, with a mechanical fit, metals of all degrees of hardness, from lead, or lead and tin, up to hardened steel may be employed, and slowly igniting powder, like that of the service may be employed.”
Mr. Whitworth’s claims.
Mr. Whitworth does not lay claim to any originality as inventor of the polygonal system, but merely brings it forward, as the most certain mode of securing spiral motion, but he deserves to be honored by all Riflemen, as having established the degree of spirality, the diameter of bore, to ensure the best results from a given weight of lead, and length of barrel.