It has been stated that amongst the different gun makers who assembled at Woolwich, for the carrying on of experiments in 1851, no two agreed upon any one thing; and in 1860, it may still be averred, with almost equal truth, and that it yet remains an unsettled question as to the form, width, depth, number or degree of spirality of the grooves, as also the harmony which should subsist between the grooves, diameter of bore, the form and weight of projectile, and the quality and quantity of charge.

Description of Rifles.

Robins, in 1742, says, “rifles though well known on the continent, being but little used in England, it is necessary to give a short description of their make. The rifle has its cylinder cut with a number of spiral channels, so that it is in reality a female screw, varying from the fabric of common screws, only in this, that its threads or rifles are less deflected and approach more to a straight line.” Advantages of a rifle.The advantage of a rifle (with a round bullet), is that the axis of rotation not being in any accidental position, as in a smooth bore, but coincident with the line of its flight, it follows that the resistance on the fore part of the bullet is equally distributed round the centre of gravity, and acts with an equal force on every side of the line of direction, and also should the resistance be greater on one side of the bullet than the other from irregularities on its surface, as this part continually shifts its position round the line in which it is proceeding, the deflections which this irregularity would occasion are neutralized. With an elongated projectile rifling also prevents it from rotating round its shorter axis.

Rifling invented in Germany.

It is to the artizans of Germany, that the rifle owes its origin, as at the close of the fifteenth century barrels with straight grooves were used by the citizens of Leipsic, at target practice, Rifles used 1498.in 1498, and the invention of grooving or rifling fire-arms is generally supposed to be the result more of accident than theory. In Dean’s Manual of fire-arms, it is stated that, “the idea of grooving arms in the direction of the axis of the barrel to receive the residium of the powder, and thereby, not only facilitate the loading, but increase both the bite or forcing of the ball, by impressing upon it the grooves, and thus maintain it during its passage through the barrel in a direction more in harmony with the line of fire, was doubtless a conception based upon no previous theory or practice now to be traced, but was formed in that suggestiveness which in the individual founds for itself a theory based upon the likelihood of possible result. Straight grooves.Upon trial also of the straight grooves a greater precision for short distances would have been observed than with the smooth bore.” This must of itself therefore have led to the establishment of a certain grade of theory which it was endeavoured to amplify by various means, such as increasing the number of grooves, then of changing the inclination of grooves from the straight line to the spiral.

To deem that the practised crack “shots and armourers of a time when target practice was the constant recreation of the citizen, and his pride to excel in, were so brainless as to conceive no theory, unelaborated though it may have been, and that all their even now admired efforts in Germany, were the products of mere accident, is therefore scarcely a rational supposition.”

Spiral grooves, by Koster, of Nuremberg in 1522.

It is stated that Koster, of Nuremburg, in 1522, first suggested giving a spiral form to the grooves, and experience proved that much greater accuracy of shooting was the result.

Damer of Nuremberg, 1552.

In 1552, Damer, of Nuremburg, made some great improvements in rifles, but we are not aware of their precise nature.

Koster of Nuremberg, 1620.

Koster, of Nuremburg, who died 1630, by some authorities is said to have discovered that straight grooves did not fulfil the intentions of their inventor, and to have been the first who suggested spiral grooves in 1620.

Robins first explained action of grooves.

The important stage next arrived at was the scientific explanation of the true value of spiral grooves. The honor of this entirely belongs to our countryman, Benjamin Robins, who in his Principles of Gunnery, gives a complete and satisfactory explanation of the action of the grooves in determining the flight of the bullet. Robins structure of rifles.Robins states that “the degree of spirality, the number of threads, the depth the channel are cut down to, are not regulated according to any invariable rule, but differ according to the country where the work is performed, and the caprice of the artificer. Modes of loading.The most usual mode of charging rifles is by forcing the ball with a strong rammer and mallet. But in some parts of Germany and Switzerland, an improvement is made by cutting a piece of very thin leather or fustian in a circular shape, somewhat larger than the bore, which being greased on one side is laid upon the muzzle with its greasy part downwards, and the bullet being placed upon it, is then forced down the barrel with it. When this is practised the rifles are generally shallow, and the bullet ought not to be too large.

Early rifles, breech-loaders.

As both these methods of charging rifles take up a good deal of time; the rifled barrels which have been made in England, (for I remember not to have seen it in any foreign piece,) are contrived to be charged at the breech, where the piece is made larger, and the powder and bullet are put in through an opening in the side of the barrel, which, when the piece is loaded is fitted up with a screw. And perhaps somewhat of this kind, though not in the manner now practised, would be of all others the most perfect method for the construction of these sorts of barrels.”

ON THE NUMBER, FORM &c., &c., &c., OF THE GROOVES.

Number of grooves.

Almost every description of twist, number, &c., &c., of grooves have been tried, according to the individual tastes and theories of the manufacturers. It is absolutely necessary to have two grooves, as a single one would give a wrong direction. Rifles have been made with, from two to one hundred and thirty three grooves, and in the majority of cases, an odd seems to have been preferred to an even number. In Dean’s Manual it is stated, Degree of spirality.that “in the numerous collections of arms that have at various times come under our personal notice, some were rifled with straight, but the majority with grooves in a spiral line, sometimes with a half, sometimes a three quarter, and seldom more than a whole turn in a length of two, two and a half and three feet; deviations based upon no principle transmitted to us, but requiring nevertheless a decided research for principles upon which to establish a theory; we have also met with every one of those configurations of the spiral and form of groove, &c., &c., which have been arrogated as modern conceits and discoveries.”

Spirality.

Some rifles have sharp muzzle twist decreasing to the breech;—sharp breech twist decreasing to the muzzle; an increase of twist in the middle of the barrel decreasing at both extremities.

Modification in France. 1740.

In France a modification of the Carabine took place in 1740;—the grooves were made to begin at eight inches from the muzzle, the unrifled part being of the same calibre as the bottom of the grooves, so that the bullet might pass easily; thus also facilitating the loading of the weapon.

Rifled only at muzzle.

There is an old rifle in the United Service Institution, and also a barrel brought from Lucknow, (in the Model Room of the School of Musketry,) grooved only for about one foot from the muzzle, the remainder of the barrels are smooth bored.

Degree of spirality.

The degree of spirality is found to vary from a whole turn in 1 foot 5-in., to a whole turn in 11 feet.

Depth of spiral.

The depth of grooves vary from ·005 of an inch, to about ·125; and some rifles have been made with an alternate deep and shallow groove.

Form of grooves.

Grooves have been made round, circular, triangular, rectangular, and indefinite, alternate round and angular, elliptical, polygonal; and some cut deep only on one side.

Proportion of groove to land.

Some gun makers are of opinion that there should be a greater proportion of groove or furrow than of land or plain surface, because they say the ball is thus more firmly held, while others maintain that by diminishing the number of the grooves, the accuracy and range would be increased, and this has led to the opposite theory, that perhaps if anything, the plain surface of the bore should predominate over the grooved.

Form of early grooves straight.

The earliest rifles had two straight deep creases opposite to each other, the bullet being spherical, and furnished with small circular knots of lead, large enough to fill the creases.

Form &c., of ancient rifles.

The greater number of ancient rifles have a whole turn, with an odd number of deep and rounded grooves; hence we may infer these were considered the best forms.

Objects of rifling.

As accuracy of direction is the result of a spiral motion round an axis coincident with the flight of the bullet, communicated to it by the grooves, it is clear that the depth, number, and form of the grooves should be such as will hold the bullet firmly, and prevent all tendency to strip.

On the degree of spirality.

The degree of spirality should be sufficient to retain the projectile point foremost during the whole of its flight. It was at one time supposed that if the spiral turn was great, and the charge strong, the bullet would not conform, but strip, and that the same results would occur even with grooves but little curved. Unquestionably this would prove true if certain limits were to be exceeded. A false conclusion was built upon this theory, viz., that the greater the spiral turn the less the charge should be; and that therefore in rifles intended for war, the greatest initial velocity being required to produce the greatest range, the groove should have as little turn as possible; for extreme ranges have been obtained with Jacob’s, Whitworth’s, and Lancaster’s rifles; the first has a full turn in 24in. the second in 20in. Sharp twist and large charge not cause stripping.These rifles perform well with 90 grains of powder, and both Whitworth’s and Lancaster’s might even fire better were the charge of powder increased to 100 grains, the recoil might be objectionable while there would be no symptoms of stripping.

On depth of groove.

Great depth of groove can only be hurtful, owing to the difficulty of closing up all passage to the gas, which should not be allowed to escape round the bullet, as this would cause deviation and shorten range. Deep grooves become a receptacle for fouling, are difficult to clean; and high projections must offer great resistance to the atmosphere, and particularly to a side wind.

Patches.

When fustian or leather are used as patches, they receive and communicate the spiral motion to the bullet, without the zone of the projectile being at all indented, but in this case the spiral must be diminished, otherwise the bullet would not turn with the grooves. If the patches be made of a thick material, the grooves should be many, broad, and not too shallow, in order to receive the folds of the patch.

Shallow grooves best.

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.

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. Cause of canting.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.

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, Polygonal rifling.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.

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. By Captain Berner, 1835.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. By Mr. Lancaster.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.

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. Favors expansion.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. Assists aiming, firing two deep: when using bayonet.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.

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; Disadvantages of short rifles.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.

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.

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.”