Chapter VII: Part 7

From our present amount of experience it seems safe to conclude that the shallower the grooves are the better, so that they perform their intended functions.

~Proportion of groove to land.~

It is now generally recommended that the grooves be made broader than the lands, _i.e._, that the rifling surface should predominate over the unrifled part of the bore. Shallow grooves with rounded edges, have the advantage of not leaving any angular traces on the surface of the bullet, besides they afford a greater facility for cleaning.

~Circular grooving.~

Circular grooving is composed of segments of circles, leaving no sharp edges on the bullet, and is no doubt a very good form.

~Gaining twist.~

~Cause of canting.~

An American gentleman named Chapman, who has written a very clever book upon the rifle, is a strong advocate for the “gaining twist,” which form prevails generally in American rifles. He states, “In a rifled barrel, it is obvious that a bullet instantaneously started from a state of rest, with a velocity of 5,000ft. a second, must exert at the moment of starting, a tendency to move along the bore in a straight line. However, meeting with the resistance that the lands employ to keep it to the twist, it communicates to the rifle itself a certain amount of motion in the direction of the twist of the creases, and this as the angle of the twist increases, combined with the size of the calibre, and the weight of the ball.”

~Remedy for canting.~

“If the angle of the twist at the breech end can be reduced, the bullet at the same time leaving the muzzle with sufficient spin to last throughout its flight, it is certain we shall have less twisting of the rifle in the marksman’s hands, less friction of the bullet against the lands, less tendency for the bullet to upset, (or be destroyed,) and consequently, from obtaining a higher velocity, (because enabled to use a greater quantity of powder,) less time for the action of regular or irregular currents of air.”

~Uniform spiral by American Government.~

After careful experiments by the American Government, preparatory to the establishing the model for their Military Rifle, it was decided that the turn for the grooves should be uniform; and that those with an increasing twist did not give any superiority of accuracy. The “gaining twist,” although adopted by Mr. Lancaster, is opposed by Mr. Whitworth, and all other Rifle manufacturers, and our increased experience does not prove it to possess any advantages over uniform spirality. Theory would indicate that it must occasion increased friction.

~Decreasing spiral.~

Mr. Greener advocates decreasing spirality. It is to be hoped he is the only advocate for so seemingly absurd an idea. To give a certain measure of spiral turn at the breech, to be withdrawn gradually as the bullet reaches the muzzle, is simply ridiculous, and which, with other conceits previously referred to, it is to be hoped are no more to be repeated.

~Polygonal rifling.~

By the desire of our first Patron, the late Lord Hardinge, Mr. Whitworth was induced to turn his mechanical genius to the Soldier’s Gun, which resulted in his adopting the polygonal form of bore. His barrel is hexagonal, and thus, instead of consisting of non-effective lands, and partly of grooves, consists entirely of effective rifling surfaces. The angular corners of the hexagon are always rounded. Supposing a bullet of a cylindrical shape to be fired, when it begins to expand it is driven into the recesses of the hexagon. It thus adapts itself to the curves of the spiral, and the inclined sides of the hexagon offering no direct resistance, expansion is easily effected.

~Westley Richards octagonal.~

Mr. Westley Richards has followed Mr. Whitworth, by using a polygonal bore, having applied his highly meritorious system of breech-loading to a barrel upon the Whitworth principle, of an octagonal form.

~Eliptic rifling.~

~By Captain Berner, 1835.~

~By Mr. Lancaster.~

The cardinal feature of this structure is, that the bore of the barrel is smooth, and instead of being circular, is cut into the form of an ellipse, i.e., it has a major and minor axis. Upon being expanded by the force of the powder, the bullet is forced into the greater axis of the ellipse, which performs the office of the grooves, rifling the projectile, and imparting to it the spiral or normal movement round its own axis. In 1835 a Captain Berner submitted his elliptical bore musket to the inspection and trial of the Royal Hanoverian Commission, appointed for that purpose, and which gave results so satisfactory, that it was considered admirably adapted for the Jäger and Light Infantry Battalions. This principle has been patented by Mr. Lancaster, and the advantages of this form have been previously adverted to.

~Odd number of grooves.~

It is supposed by some persons that if the number of grooves be even, so that they will be opposite to one another, the bullet would then require more force to enlarge it, so as to fill them properly. If the number be unequal, the lands will be opposite to the grooves, and the lead, in forcing, spreading on all sides, will encounter a land opposite to each groove, which will in some measure repel it, and render its introduction into the opposite groove more complete.

This ingenious theory is set at nought by Whitworth, Jacobs, Lancaster, W. Richards, &c., &c., who all recommended an even number of grooves, while the Government arms have an odd number.

~Drift or cant.~

If the grooves twist or turn over from left to right, the balls will be carried to the right; and if from right to left, they will group to the left; and this result will be great in proportion to the degree of spirality. The causes of Drift or “Derivation” will be treated of hereafter. We know from observation that the majority of balls strike to the right of the mark. The recoil and _pulling_ the trigger throw back the right shoulder, which tend to increase the “derivation” to the right. If the twist were, then, from _right_ to _left_, the drift, error from _pulling_, and from recoil, would tend to neutralize each other; the twist of the grooves should therefore be from right to left, instead of the present universal practice of from _left_ to right.

~On length of barrel.~

~Favors expansion.~

~Assists aiming, firing two deep: when using bayonet.~

The barrel of a gun may be looked upon as a machine in which force is generated for the propulsion of the bullet. It is well known that the continued action of a lesser force, will produce a much greater effect, than a greater amount of power applied suddenly; hence mild gunpowder is more suitable for rifle shooting than strong, or that which evolves the whole of its gas instantaneously. Time is necessary for the entire combustion of a charge of gunpowder, consequently more mild gunpowder can be fired out of a long, than out of a short barrel, as if fired out of a short barrel, some of the grains might be ejected unconsumed. All extra length, after the last volume of gas is evolved, can only be injurious, by causing loss of velocity from friction. A billiard ball would travel none the further nor straighter, were it to be propelled through a hollow tube, neither would a barrel to a cross bow aid in killing rooks. A barrel favours expansion of the bullet, which is produced by the force of the generated gas, opposed by the column of air in the hollow tube and by the motion of the projectile. Facility in aiming is promoted by the sights being distant from each other. In a military arm a certain length is necessary in order to fire when two deep in the ranks, and length is also advantageous, should the rifle be used as a pike.

~Advantages of short rifle.~

~Disadvantages of short rifles.~

The short rifle can be held steadier when standing, by a weak man, and during wind, it is handy when passing through a wood or thicket, and a very short man has more command of his gun when loading; but with the sword bayonet, it is heavier than the long Enfield and bayonet; while the sword is very inconvenient when running, firing kneeling, or lying down.

~Thickness of barrel.~

Great substance was at one time considered necessary for accurate firing, it being supposed necessary to prevent vibrations in the barrel; this is true within certain limits, and the heavier the charge, the heavier the metal ought to be, especially at the breech, but diminishing the thickness, has been proved in no wise to lessen the accuracy. A heavy barrel also lessens recoil, but it would be folly to carry more weight than would neutralize the recoil which could be produced by a greater charge of powder than could be consumed in a given length of barrel.

~Size of bore.~

The two grand requirements of a soldier’s gun are, celerity of loading, combined with accuracy at long ranges; and the distance at which he should have the power of firing, should be limited by the strength of his eye. The weight of the projectile being fixed (·530 grs.), good shooting at extreme distances can only be obtained by reducing the diameter of the bore, which, lessening the frontage of the bullet, causes it to experience less resistance from the air; it therefore retains a higher degree of velocity than a larger bullet of the same form and weight, and therefore travels further and faster. Gravity has less time to act upon it, in a given distance, and therefore it can be fired at a lower angle, or has what we call a lower trajectory, and its accuracy is increased in direct proportion to the lowness of its flight, all other things being equal.

~Best form of rifling still undetermined.~

While the best form, &c., &c., for rifles is not yet determined, there are many points upon which the generality of persons seem more agreed, viz., reduction of bore to about ¹⁄₂-in. in diameter, fewer grooves, shorter barrel, and with increased spirality; at least, one may safely say that ideas seem to travel in this direction.

ON RIFLE PROJECTILES.

~Projectiles used in early guns.~

~Elliptical iron bullets 1729.~

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. 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.~

~1800 and 1815.~

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. 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.~

~Cork plug 1851.~

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; 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.~

~Form of leaden bullet destroyed.~

~Zinc point to bullets.~

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, 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. 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).

~Groove suppressed.~

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, 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.~

~Many cannelures.~

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, 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.~

~Action of the air.~

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. 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.~

~Cause of deviation.~

~Remedy.~

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. 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,” 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.~

~By the arrow.~

~Use of feathers on arrows.~

If, however, we would wish to obtain some idea of the rotatory motion of a bullet in its path through the air, 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. 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.

~Effect of grooves.~

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). 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.~

~Why none in English bullet.~

Captain Jervis says that these grooves have the effect of improving the accuracy of firing when the bullets are not perfectly homogeneous, is certain, 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.~

~Auxiliaries to expansion, various.~

Almost every conceivable form of projectile, internal and external, have been made and experimented upon. 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.~

~Points in a perfect rifle.~

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, 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.

~Result of Mr. Whitworth’s experiments.~

In the foregoing brief summary of the most important properties which should be possessed by a first class rifle, we have dealt in generalities, 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.~

~Diameter of bore determined.~

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, 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.~

~Effects of quick 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. 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.~

~Diameter decreased.~

~Trajectory lowered.~

“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, and a reduced diameter, 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.~

~Powder for hardened bullets.~

~Consequences of imperfect expansion.~

~Advantages of hexagonal form.~

“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, 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. 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. 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.

CONCLUSION.

In achieving the important position obtained by the rifle in the present day, it has nevertheless effected no more than was predicted of it by Leutman, the Academician of St. Petersburg, in 1728, by Euler, Borda, and Gassendi, and by our eminent but hitherto forgotten countryman Robins, who in 1747, urgently called the attention of the Government and the public to the importance of this description of fire-arm as a military weapon.

In the War of American Independence, the rifle, there long established as the national arm for the chase, exhibited its superiority as a _war_ arm also, in so sensible a manner, that we were constrained to oppose to the American hunters the subsidised Riflemen of Hesse, Hanover, and Denmark.

~Robins’ prophecy.~

We shall close by quoting the last words in “Robins’ Tracts of Gunnery.”

“Whatever State shall thoroughly comprehend the nature and advantages of rifled barrel pieces, and having facilitated and completed their construction, shall introduce into their armies their _general_ use with a _dexterity_ in the _management_ of them; they will by this means acquire a superiority, which will almost equal anything that has been done at any time by the particular excellence of any one kind of arms; and will perhaps fall but little short of the wonderful effects which histories relate to have been formerly produced by the first inventors of fire-arms.”

NOTE.--The preceding articles on the Rifle, Rifling, and Rifle
Projectiles are mainly compiled from: “New Principles of Gunnery, by
Robins,” “Scloppetaria,” “Remarks on National Defence, by Col. the
Hon. A. Gordon,” “Dean’s Manual of Fire Arms,” “Rifle Ammunition, by
Capt. A. Hawes,” “Rifles and Rifle Practice, by C. M. Wilcox,” “Papers
on Mechanical Subjects, by Whitworth,” “The Rifle Musket, by Capt.
Jarvis, Royal Artillery,” “Des Armes Rayees, by H. Mangeot,” “Cours
Elementaire sur les Armes Portatives, by F. Gillion,” and “Cours sur
les Armes a feu Portatives, by L. Panot.”

THEORETICAL PRINCIPLES.

DEFINITIONS.

~Matter.~

Matter,--everything which has weight.

~Body.~

Body,--a portion of matter limited in every direction.

~Mass.~

Mass,--the quantity of matter in any body.

~Particle.~

Particle,--or material point, is a body of evanescent magnitude, and bodies of finite magnitude are said to be made up of an indefinite number of particles, or material points.

~Inertia.~

Inertia,--passiveness or inactivity.

~Attraction.~

Attraction,--a fundamental law of nature, that every particle of matter has a tendency to be attracted towards another particle.

~Density.~

Density,--is in proportion to the closeness of the particles to each other.

~Volume.~

Volume,--the space bounded by the exterior surface of a body, is its apparent volume or size.

~Elasticity.~

Elasticity,--a body that yields to pressure, and recovers its figure again; hence air and gasses are elastic bodies; lead a non-elastic body.

~Motion.~

Motion,--is the changing of place, or the opposite to a state of rest.

~Velocity.~

Velocity,--is the rate of motion; there are four rates of motion, viz., Uniform, Variable, Accelerated, and Retarded.

~1st. Uniform.~

1st. Uniform,--when a particle traverses equal distances, in any equal successive portion of time.

~2nd. Variable.~

2nd. Variable,--when the spaces passed over in equal times, are unequal.

~3rd. Accelerated.~

3rd. Accelerated,--when the distances traversed in equal times are successively greater and greater.

~4th. Retarded.~

4th. Retarded,--when the distances traversed in equal times are successively less and less.

Acceleration or Retardation, may also be equal or unequal, that is uniform or variable.

~Friction.~

Friction,--arises from the irregularities of the surfaces which act upon one another.

~Force.~

Force,--any cause which produces, or tends to produce a change in the state of rest, or of motion of a particle of matter.

~Measure of force.~

Forces are measured by comparison with weights. Thus any forces which will bend a spring into the same positions as weights of 1lb., 2lbs., 3lbs., &c., are called respectively forces of 1lb., 2lbs., 3lbs., &c., &c.

~Momentum.~

Momentum,--or quantity of motion. If a body moving at first with a certain velocity is afterwards observed to move with double or triple this velocity, the quantity of motion of the body is conceived to be doubled or tripled, hence the momentum of a body, depends upon its velocity, as the quantity of motion of a body is the product of the velocity by the mass or weight.

~Laws of motion.~

The elementary principles upon which are based all our reasonings respecting the motions of bodies, are called the “Laws of Motion,” and as arranged by Sir Isaac Newton, are three in number.

~1st Law.~

1st. A particle at rest will continue for ever at rest, and a particle in motion will continue in motion uniformly forward in a straight line, until it be acted upon by some extraneous force.

~2nd Law.~

2nd. When any force acts upon a body in motion, the change of motion which it produces is proportional to the force impressed, and in the direction of that force.

~3rd Law.~

3rd. Action and reaction are equal, and in contrary directions. In all cases the quantity of motion gained by one body is always equal to that lost by the other in the same direction. Thus, if a ball in motion, strikes another at rest, the motion communicated to the latter will be taken from the former, and the velocity of the former be proportionately diminished.

~Centre of Gravity.~

Centre of Gravity,--is that point at which the whole weight of the body may be considered to act, and about which consequently, the body, when subjected to the force of gravity only, will balance in all positions.

~Specific Gravity.~

Specific Gravity,--the weight belonging to an equal bulk of every different substance, and is estimated by the quantities of matter when the bulks are the same; or in other words, it is the density that constitutes the specific gravity. It is agreed to make pure rain-water the standard, to which they refer the comparative weights of all other bodies. Lead is about eleven times the weight of the same bulk of water.

~Initial Velocity.~

Initial Velocity is the velocity which a bullet possesses on leaving the muzzle of a gun; and in the speaking of the velocity of bullets fired from the musket now used, you understand 1200 feet per second, for the Initial Velocity.

~Angular Velocity.~

Angular Velocity is the velocity with which the circular arc is described; and depends upon the perpendicular distance of the point from the axis of rotation.

~Terminal Velocity.~

Terminal Velocity: if a cannon ball were to be let fall from a very great height, it would by the law of gravity, descend with accelerated motion towards the earth, but as the resistance of the air increases as the squares of velocities, a point would be reached when the resistance would be equal to the force of gravity, from whence it would fall to the earth in uniform motion.

~Eccentric Body.~

An Eccentric Body, is one whose centre of figure does not correspond with the centre of gravity.

MOTION OF A PROJECTILE.

~Modified by Gravity and air.~

If no force were acting upon the projectile, except the explosive force of gunpowder, it would by the first law of motion, move on for ever in the line in which it was discharged; this motion is modified by the action of two forces, viz., gravity and the resistance of the air.

As the early cannons were of the rudest construction, and were used only to force open barriers, or to be employed against troops at a very short range, it was a matter of secondary consideration what course the bullet took, indeed it was generally believed, that it flew for some distance in a straight line, and then dropped suddenly. Acting upon this opinion we find that most of the early cannon had a large metal ring at the muzzle, so as to render it the same size as at the breech, and with such as were not of this construction they made use of a wooden foresight which tied on to the muzzle, so as to make the line of sight parallel to the axis, by which they conceived that they might aim more directly at the object which the bullet was designed to hit.

~Leonardo da Vinci, 1452.~

The first author who wrote professedly on the flight of a cannon shot was a celebrated Italian Mathematician, named Leonardo da Vinci, who explains his manner of studying phenomena, in order to arrive at safe conclusions, thus: “I will treat of the subject, but first of all I will make some experiments, because my intention is to quote experience, and then to show why bodies are found to act in a certain manner;” and taking as his motto, “Science belongs to the Captain, practice to the Soldier,” he boldly asks: “If a bombard throws various distances with various elevations, I ask in what part of its range will be the greatest angle of elevation?” The sole answer is a small drawing of three curves, (plate 20, fig. 3.), the greatest range being the curve about midway between the perpendicular and the horizontal. Yet this small drawing is very remarkable when we come to examine it. In the first place, we see that he recognises the fact that the trajectory is a curve throughout its length; secondly, that a shot fired perpendicularly will not fall again on the spot whence it was fired. Simple as they may seem, these two propositions recognise the force of gravity, resistance of the air, and the rotary motion of the earth.

~Tartaglia, 1537.~

The next author who wrote on the flight of cannon shot was another celebrated Italian Mathematician, named Tartaglia. In the year 1537, and afterwards in 1546, he published several works relating to the theory of those motions, and although the then imperfect state of mechanics furnished him with very fallacious principles to proceed on, yet he was not altogether unsuccessful in his enquiries, for he determined (contrary to the opinion of practitioners) that no part of the track of a bullet was in a straight line, although he considered that the curvature in some cases was so little, as not to be attended to, comparing it to the surface of the sea, which, although it appears to be a plain, when practically considered, is yet undoubtedly incurvated round the centre of the earth. It was only by an accident he nearly stumbled upon one truth in the theory of projectiles, when he stated that the greatest range obtained by equal forces is at 45°. Calculating that at the angle 0° the trajectory was null, that by raising the trajectory, the range increased up to a certain point, afterwards diminished, and finally became null again when the projective force acted perpendicularly, he concluded that the greatest range must be a medium between these two points, and consequently at 45°.

Others thought that a shot, on leaving the muzzle, described a straight line; that after a certain period its motion grew slower, and then that it described a curve, caused by the forces of projection and gravity; finally, that it fell perpendicularly. Tartaglia seems to have originated the notion that the part of the curve which joined the oblique line to the perpendicular, was the arc of a circle tangent to one and the other.

~Galileo, 1638.~

In the year 1638, Galileo, also an Italian, printed his dialogues, in which he was the first to describe the real effect of gravity on falling bodies; on these principles he determined, that the flight of a cannon shot, or of any other projectile, would be in the curve of a parabola, unless it was deviated from this track by the resistance of the air. A parabola is a figure formed by cutting a cone, with a plain parallel to the side of the cone.

GRAVITY.

~Bullet as influenced by powder and gravity only.~

We will now proceed to consider the course of a bullet, as affected by _two_ forces only, viz., 1st. The velocity communicated to it by the explosion of the powder; and 2nd. By the force of Gravity.

The attraction of the earth acts on all bodies in proportion to their quantities of matter.

~If no air, all bodies would fall in same time.~

~Gold and dry leaf in same time.~

The difference of time observable in the fall of bodies through the air, is due to the resistance of that medium, whence we may fairly conclude, that if the air was altogether absent, and no other resisting medium occupied its place, all bodies of whatever size, and of whatever weight, must descend with the same speed. Under such circumstances, a balloon and the smoke of the fire would descend, instead of ascending as they do, by the pressure of the air, which, bulk for bulk, is heavier than themselves. A dry leaf falls very slowly, and a piece of gold very rapidly, but if the gold be beaten into a thin leaf, the time of its descent is greatly prolonged. If a piece of metal and a feather are let fall at the same instant from the top of a tall exhausted receiver, it will be found that these two bodies, so dissimilar in weight, will strike the table of the air-pump, on which the receiver stands, at the same instant. Supposing the air did not offer any resistance to the onward course of a projectile, and that the instantaneous force communicated to a bullet, from the explosion of the gunpowder, were to project it in the line A.B. (plate 21, fig. 4.) from the point A., with a velocity that will send it in the first second of time as far as C., then if there were no other force to affect it, it would continue to move in the same direction B., and with the same velocity, and at the next second it would have passed over another space, C.D., equal to A.C., so that in the third second it would have reached E., keeping constantly in the same straight line.

~Bullet under two forces, powder and gravity.~

But no sooner does the bullet quit the muzzle, than it immediately comes under the influence of another force, called the force of gravity, which differs from the force caused by the explosion of the powder, which ceases to influence the bullet, after it has once communicated to it its velocity.

~An accelerating force.~

~Effect of gravity.~

Gravity is an accelerating force, acting constantly upon, and causing the bullet to move towards the earth, with a velocity increasing with the length of time the bullet is exposed to its influence. It has been found from experiment that this increase of velocity will cause a body to move through spaces, in proportion to the squares of the time taken to pass over the distance. Thus, if a body falls a given space in one second, in two it will have fallen over a space equal to four times what it fell through in the first second, and in the three first seconds it will have fallen through a space equal to nine times that which it fell through in the first second.

~Result of gravity.~

~Course of the bullet.~

The consequence of this principle is, that all bodies of similar figure, and equal density, at equal distances from the earth, fall with equal velocity; and if a body describes a space of 16ft. in the first second of time, it will, in the next second of time, fall _three_ times 16, or 48 feet, and thus will have fallen, from the time it first dropped, four times 16 feet, or 64 feet, because 4 is the square of 2, the time the body was falling. In the third second, it will fall 5 times 16 feet, or 80 feet, and these sums collectively, viz., 16 + 48 + 80 = 144 feet, the whole distance described by the falling body in three seconds of time.

From this it is evident, that instead of moving in a straight line A. B., (plate 21, fig. 5.), the bullet will be drawn from that course.

~Parabolic theory.~

From the point C., draw C. F., equal to the space that the bullet may be supposed to fall in one second of time, then at the end of the first second of time the bullet will be at F., instead of at C., and will have moved in the direction A. F., instead of A. C.; at the end of the next second it will have fallen a total distance D. G., equal to four times C. F., thus the bullet will have fallen at the end of the third second a distance E. H., equal to nine times C. F., and it will have moved in the line A. F. G. H. instead of the straight line A. B., in which it would have moved, had it not been affected by the force of gravity. The curve A. H., is of the form called a Parabola, and hence the theory is called the “Parabolic Theory.” It is founded on the principle that the velocity given to the bullet by the explosion of the gunpowder is continued throughout its course, but this would only be true in vacuo, and is therefore of little value in calculating the real course of the bullet in the air.