On Rifled Cannon

[New-York Daily Tribune, No. 5914, April 7, 1860]

The first attempts at increasing the range and precision of ordnance by rifling the bore, and thereby giving the shot a rotation vertical to the line of propulsion, date from the 17th century. There is a small rifled gun at Munich, manufactured in Nuremberg in 1694; it has eight grooves and a bore of about two inches diameter. During the whole of the 18th century, experiments were made, both in Germany and in England, with rifled cannon, some of them breech-loading. Though the calibers were small, the results obtained were very satisfactory; the English two-pounders in 1776, at a range of 1,300 yards, gave a lateral deflection of two feet only—a degree of precision which no other gun at the time was capable of approaching. In the same year, these rifled cannon were for the first time used for projecting oblong shot.

These experiments, however, remained for a long while without any practical results. The current of military opinion at that time altogether went against rifled arms. The rifle itself was then a very clumsy instrument, its loading was a slow and tedious operation, requiring considerable skill. It was a weapon unfit for general warfare at a period when rapid firing, whether of deployed lines, of heads of columns, or of skirmishers, was one of the chief desiderata in battle. Napoleon would have no rifles in his army; in England and Germany, a few battalions only were equipped with them; in America and Switzerland alone, the rifle remained the national weapon.

The Algerian war was the occasion to bring the rifle again into credit, and to cause improvements in its construction which were but the beginning of that colossal revolution in the whole system of firearms which is even now far from its conclusion. The smooth-bore muskets of the French were no match for the long espingardas of the Arabs; their greater length and better material, which admitted of a heavier charge, enabled the Kabyles and Bedouins to fire on the French at distances where the regulation musket was utterly powerless. The Duke of Orleans[a], having seen and admired the Prussian and Austrian chasseurs, organized the French chasseurs on their model, who soon, for armament, equipment, and tactics, became the first troops of their class in the world. The rifle with which they were armed was far superior to the old rifle, and it soon underwent further changes, resulting, finally, in the general introduction of rifled muskets in the whole of the infantry of Europe.

The range of infantry fire having thus been increased from 300 to 800, and even 1,000 yards, the question arose whether field artillery, which hitherto had commanded all distances from 300 up to 1,500 yards, would still be able to hold its own against the new small-arms. The fact was, that the greatest efficacy of common field guns lay just within that range which was now disputed to it by the rifle; canister was scarcely effective beyond 600 or 700 yards; round shot gave no very satisfactory results, with the six or nine-pounder, beyond 1,000 yards; and shrapnel (spherical case-shot), to be very formidable, required a coolness and a correct estimation of distances which are not always to be found on the field of battle, when the enemy is advancing; while the shell-practice of the old howitzers against troops was anything but satisfactory. The armies which had the nine-pounder gun for their smallest caliber, such as the English, were still the best off ; the French eight-pounder, and, still more, the German six-pounder, became almost useless. To obviate this, the French introduced, about the beginning of the Crimean war, Louis Napoleon's so-called invention, the light twelve-pounder, canon obusier[b], from which solid shot, with a charge of one-fourth instead of one-third its weight, as well as shell, was to be fired. This gun was a mere plagiarism upon the English light twelve-pounder, which had already been again abandoned by the English; the system of firing shells from long guns had been long in practice in Germany; so that there was nothing at all new in this pretended improvement. Still, the arming of the whole French artillery with 12-pounders, even of a diminished range, would have given it a decided superiority over the old 6 and 8-pounders; and to counteract this, the Prussian Government, in 1859, resolved upon giving heavy 12-pounders to all its foot batteries. This was the last move in the cause of the smooth-bore gun; it showed that the whole subject was exhausted, and the defenders of the smooth-bore driven ad absurdum. There could, indeed, not be anything more absurd than to arm the whole artillery of an army with those lumbering, stick-in-the-mud Prussian 12-pounders, and that at a time when mobility and rapidity of maneuvering is the greatest desideratum of all. The French light 12-pounder having a relative superiority only to other artillery, and none at all as regarded the new small-arms, and the Prussian heavy 12-pounder being a palpable absurdity, there remained nothing but either to drop field artillery altogether, or to adopt rifled cannon.

In the mean time, experiments with rifled cannon had continually been carried on in various countries. In Germany, the Bavarian Lieut.-Col. Reichenbach experimented with a small rifled gun and cylindro-conoidal shot, as early as 1816. The results were very satisfactory as to range and precision, but the difficulties of loading and extraneous obstacles prevented the subject from being followed up. In 1846, the Piedmontese Major Cavalli constructed a breech-loading rifled gun which attracted considerable attention. His first gun was a thirty-pounder, charged with a cylindroconoidal hollow shot weighing 64 pounds, and 5 pounds powder; at 14¾ degrees elevation he obtained a range (of first gauge) of 3,050 metres or 3,400 yards. His experiments (continued up to the latest period, partly in Sweden, partly in Piedmont) had the important result of leading to the discovery of the regular lateral deflection of all shot fired from rifled ordnance, which is caused by the pitch of the grooves, and which is always in the direction to which the grooves turn; this once being ascertained, its correction by what is called a lateral or horizontal tangent-scale, was also invented by Cavalli. The results of his experiments were highly satisfactory. At Turin, in 1854, his thirty-pounder, with 8-pound charges, 64-pound shot, gave the following results:

giving a range, at 25 degrees, of above three miles, with a lateral deflection from the line of aim (as corrected by the horizontal tangent-scale) of less than 16 feet! The largest French field howitzer, at a range of 2,400 metres, equal to 2,650 yards, gave lateral deflections averaging 47 metres, or 155 feet; ten times as large as those of the rifled gun at twice the range.

Another system of rifled ordnance which created attention, a little after Cavalli's first experiments, was that of the Swedish Baron Wahrendorff. His gun was also breech-loading, and his shot cylindro-conoidal. The difference, however, in the shot was this: while Cavalli's shot was of hard metal, and had wings to fit in the grooves, Wahrendorff's shot was covered with a thin layer of lead, and slightly larger in diameter than the bore of the rifled portion of the gun. After being introduced into the chamber, which was large enough to receive it, the shot was propelled by the explosion into the rifled bore, and the lead being pressed into the grooves effectually, did away with all windage, and prevented the escape of any portion of the gases formed by the explosion. The results obtained with these guns in Sweden and elsewhere were quite satisfactory, and if Cavalli's guns were introduced into the armament of Genoa, those of Wahrendorff figure in the casemates of Waxholm in Sweden, Portsmouth in England, and in some Prussian fortresses. Thus, the introduction of rifled ordnance into practical use had begun, although only for fortresses. There remained only the one step to introduce them into field artillery, and this has been done in France and is now being done in all European artilleries. The various systems on which the rifling of field ordnance is now, or may be, profitably carried on, will form the subject of a second paper.

[New-York Daily Tribune, No. 5926, April 21, 1860]

The French were, as we said in our preceding paper, the first to introduce rifled cannon into practical warfare. For five or six years past, two officers, Col. Tamisier and Lieut.-Col. (now Col.) Treuille de Beaulieu, had experimentalized on the subject by order of the Government, and the results arrived at were found satisfactory enough to warrant their being made the base of a reorganization of the French artillery immediately before the outbreak of the late Italian war. Without entering upon the history of the experiments, we will at once pass to a description of the system now adopted in the French artillery.

In accordance with that desire for unity so characteristic of the French, they adopted one caliber only for field artillery (the old French four-pounder bore of 85½ millimetres, or nearly 3½ inches), and one for siege artillery (the old 12-pounder of 120 millimetres, or 4¾ inches). All other guns, except mortars, are to be done away with. The material selected is generally the common gun-metal, but also cast-steel, in some cases. The guns are muzzle-loading, as the French experiments with breech-loaders gave no satisfaction. There are six grooves in each gun, 5 millimetres deep and 16mm. broad, of a rounded form; the pitch - of the rifling appears to be but low, but there are no details known respecting it. The windage on the body of the shot is about ½ to 1 mm.; that on the ailettes or warts which enter the grooves rather less than 1 mm. The shot is cylindro-ogival, and hollow, weighing about 12 pounds when filled; it has six ailettes, one for every groove, three standing near the point, and three near the base; they are very short—about 15 mm. long. The fuse-hole passes downward from the point, and is closed by a fuse or by a piston, with a percussion-cap for shot filled with powder, and by an iron screw, when the shot is not to explode; in this latter case it is filled with a mixture of sawdust and sand, so as to give it the same weight as when filled with powder. The length of bore of the gun is 1,385 mm., or 16 times its diameter; the weight of the brass gun is but 237 kilogrammes (518 pounds). To regulate the line of aim by the deviation (lateral deflection) of the shot in the direction of the pitch of the rifling—a deviation common to all projectiles launched from rifled barrels—the right trunnion carries what is called a horizontal tangent-scale. The gun, as well as its carriage, is reported to be of very elegant, workmanship, and, from its small size and neatness, to look more like a model than a real engine of war.

Armed with this gun, the French artillery entered upon the Italian campaign, where it indeed astonished the Austrians by its great range, but certainly not by its accuracy of fire. The guns very often, indeed generally, overshot the mark, and were more dangerous to reserves than to first lines—in other words, where they hit better than the common guns, they hit people at whom they were not aimed at all. This is certainly a very questionable advantage, as in nine cases out of ten it implies that the objects at which the guns were aimed were not hit. The Austrian artillery, with as clumsy a material as any in Europe, made a very decent appearance when opposed to them, and came up to close quarters (that is, 500 or 600 yards) with these formidable opponents, unlimbering under their most effective fire. There is no doubt that, great as the superiority of the new French guns is over their old smooth-bored ones, they did not perform anything like what was expected from them. Their extreme practicable range was 4,000 metres (4,400 yards), and undoubtedly it was but an impudent Bonapartist exaggeration when it was said that they could easily hit a single horseman at 3,300 yards.

The reasons for these unsatisfactory performances, in actual war, are very simple. The construction of these guns is utterly imperfect, and if the French adhere to it, in two or three years their artillery will possess the worst materiel in Europe. The first principle in rifled arms is that there must be no windage; otherwise the shot, loosely rolling about in the barrel and grooves, will not rotate round its own longitudinal axis, but rotate, in a spiral line of flight, round an imaginary line, the direction of which is determined by the accidental position of the shot when leaving the muzzle, and the spiral rounds will increase in diameter with the distance. Now, the French guns have considerable windage, and cannot do without it so long as the explosion of the charge is relied upon to light the fuse of the shell. This, then, is one circumstance which explains the Want of accuracy. The second is the irregularity of the propelling force created by the greater or less escape of gas through windage during the explosion of the charge. The third is the greater elevation, with the same charge, necessitated through this windage; it stands to reason that where no gas at all can escape between shot and bore, the same charge propels further than where part of the gas- escapes. Now, the French guns appear to require not only a very great charge for rifled guns (one-fifth of the weight of the shot), but also a pretty high elevation. The greater range obtained by rifled bores over smooth ones, even with smaller charges, is chiefly obtained by the absence of windage, and the certainty of having the whole explosive force of the charge applied to the expulsion of the shot. By admitting windage, the French sacrifice part of the propelling force, and have to replace it by increased charges to a limited degree, and by greater elevation beyond that. Now, there is nothing so contrary to accuracy at any distances as great elevation. So long as the line of flight of the shot does not, at its highest point, much exceed the hight of the object aimed at, so long a mistake in estimating the distance is of little importance; but at long range, the shot takes a very high flight, and comes down at an angle on an average twice as great as that under which it began its flight (this, of course, is confined to elevations up to about 15 degrees). Thus, the higher the elevation the more the line in which the shot strikes the ground approaches the vertical; and an error in estimating the distance of not more than ten or twenty yards may preclude the possibility of hitting at all. At ranges beyond even 400 or 500 yards, such errors are unavoidable, and the consequence is the astonishing difference between the capital shooting on the practice-ground, with measured distances, and the execrable practice on the battle-field, where the distances are unknown, the objects moving, and the moments for reflection very short. Thus, with the new rifles, the chance of hitting beyond three hundred yards on the battle-field is very small, while under three hundred yards, from the low flight of the ball, it is very great; in consequence of which, the charge with the bayonet becomes the most effective means of dislodging an enemy, as soon as the attacking body has come up to that distance. Suppose one army to carry rifles which at 400 yards give no higher trajectory than the rifles of their opponents give at 300 yards, the former will have the advantage of beginning an effective fire at 100 yards greater distance, and as but three or four minutes are required to. charge through 400 yards, this advantage is not a mean one in the decisive moment of a battle. It is similar with cannon. Sir Howard Douglas, ten years ago, declared[c] that gun far the best which gives the greatest range with the least elevation. With rifled cannon the importance of this point is still greater, as the chance of error in estimating distance increases with the longer range, and as the ricochets of any other than spherical shot cannot be relied upon. This is one of the disadvantages of rifled guns; they must hit with the first impact, if they are to hit at all, while round-shot, if it falls short, will rebound and continue its flight in very nearly its original direction. Here, then, a low trajectory is of the very highest importance, as every degree more of elevation reduces the chance of hitting with the first impact in an increasing ratio, and therefore the high line of flight produced by the French guns is one of their most serious defects.

But the whole of the deficiencies of these guns are crowned and enhanced by one defect, which suffices to stamp the whole system. They are produced by the machinery and on the principles formerly serving for the manufacture of the old smooth-bored guns. With the very great windage of these old guns, and the varying weights and diameters of the shot, mathematical precision in the manufacture was but a secondary consideration. The manufacture of firearms, up to a very few years ago, was the most backward branch of modern industry. There was far too much hand labor and far too little machinery. For the old smooth-bore arms this might be allowable; but when arms were to be manufactured which were expected to have great precision at long distances, this system became intolerable. To insure the certainty that every musket should shoot perfectly alike at 600, 800, 1,000 yards, and every cannon at 2,000, 4,000, 6,000 yards, it became necessary that every part of every operation should be performed by the most perfect and self-acting machinery, so as to turn out one weapon the mathematical counterpart of the other. Deviations from mathematical precision, inappreciable under the old system, now became defects rendering the whole weapon useless. The French have not improved their old machinery to any noticeable extent, and hence the irregularities in their firing. How can guns be made to give the same range at the same elevation, all other circumstances being alike, when none of them is identical with the other in every particular? But irregularities in manufacture which at 800 yards produce differences of a yard, at 4,000 will produce differences of a hundred yards in range. How, then, can such guns be expected to be true at long ranges?

To recapitulate: the French rifled guns are bad, because they must have windage; because they require, comparatively, great elevations, and because their workmanship is not at all up to the requirements of rifled long-range guns. They must soon be superseded by different constructions, or they will reduce the French artillery practice to the worst in Europe.

We have purposely examined these guns a little in detail, as they gave us, thereby, an opportunity of explaining the chief principles of rifled ordnance. In a concluding article we shall consider the two systems proposed, which in England are now contesting for superiority—systems both of which are founded upon loading by the breech, absence of windage, and perfect workmanship the Armstrong system and that of Whitworth.

[New-York Daily Tribune, No. 5938, May 5, 1860]

We now come to the description of the two kinds of breech-loading rifled cannon which at the present moment contend for superiority in England, and which, both invented by civilians, certainly surpass in efficiency anything hitherto produced by professional artillerists—the Armstrong gun and the Whit-worth gun.

Sir William Armstrong's gun had the advantage of priority, and of being praised by the whole press[d] and official world of England. It is, undoubtedly, a highly effective machine of war, and far superior to the French rifled gun; but whether it can beat Whitworth's gun may well be doubted.

Sir Wm. Armstrong constructs his gun by wrapping, round a tube of cast steel, two layers of wrought-iron tubes in a spiral form, the upper layer laid on in the opposite direction to the lower one, in the same way as gun-barrels are made from layers of wire. This system gives a very strong and tough material, though a very expensive one. The bore is rifled with numerous narrow grooves, one close to the other, and having one turn in the length of the gun. The oblong—cylindro-ogival—shot is of cast iron, but covered with a mantle of lead, which gives it a diameter somewhat larger than the bore; this shot, along with the charge, is introduced by the breech into a chamber wide enough to receive it, the explosion propels the shot into the narrow bore, where the soft lead is pressed into the grooves, and thus does away with all windage while giving the projectile the spiral rotation indicated by the pitch of the grooves. This mode of pressing the shot into the grooves, and the coating of soft material required for it, are the characteristic features of Armstrong's system; and if the reader will refer to the principles of rifled ordnance, as developed in our preceding articles, he will agree that, in principle, Armstrong is decidedly in the right. The shot being larger in diameter than the bore, the gun is necessarily breech-loading, which, to us, also seems a necessary feature in all rifled ordnance. The breech-loading apparatus itself, however, has nothing whatever to do with the principle of any particular system of rifling, but may be transferred from one to the other; we leave it, therefore, entirely out of our consideration.

The range and precision attained with this new gun are something wonderful. The shot was thrown to some 8,500 yards, or nearly five miles, and the certainty with which the target was hit at 2,000 or 3,000 yards much exceeded what the old, smooth-bore guns could show at one-third of these distances. Still, with all the puffing of the English press, the scientifically interesting details of all these experiments were studiously kept secret. It was never stated with what elevation and charge these ranges were obtained; the weight of the shot and that of the gun itself, the exact lateral and longitudinal deviations, &c., were never particularized. Now, at last, when the Whitworth gun has made its appearance, we learn some details of one set of experiments at least. Mr. Sidney Herbert, Secretary of War, has stated in Parliament[e] that a 12-pounder gun of 8 cwt., with 1 lb. 8 oz. of powder, gave a range of 2,460 yards, at 7 degrees elevation, with an extreme lateral deviation of three, and an extreme longitudinal deviation of 65 yards. At eight degrees elevation, the range was 2,797 yards; at nine, above 3,000 yards; the deviations remaining nearly the same. Now, an elevation of seven to nine degrees is a thing unknown in the practice of smooth-bore field artillery. The official tables, for instance, do not go beyond four degrees elevation, at which the 12-pounder and 9-pounder give a range of 1,400 yards. Any higher elevation in field guns would be useless, from giving too high a line of flight, and thereby immensely reducing the chance of hitting the mark. But we have some experiments (quoted in Sir Howard Douglas's Naval Gunnery) with heavy ship guns of smooth bore at higher elevations. The English long 32-pounder at Deal, in 1839, gave ranges, at 7 degrees, of 2,231 to 2,318; at 9 degrees, from 2,498 to 2,682 yards[f]. The French 36-pounder, in 1846 and '47, gave ranges, at 7 degrees, of 2,270; at 9 degrees, of 2,636 yards[g]. This shows that, at equal elevations, the ranges of rifled guns are not so very superior to those of smooth-bore cannon.

The Whitworth gun, in almost every respect, is the opposite of the Armstrong gun. Its bore is not circular, but hexagonal; the pitch of its rifling is very near twice as high as that of the Armstrong gun; the shot is of a very hard material, without any coating of lead; and, if it is breech-loading, it is not necessarily so, but merely as a matter of convenience and of fashion. This gun is of a recently-patented material, called "homogeneous iron," of great strength, elasticity, and toughness; the shot is a mathematically exact fit to the bore, and cannot, therefore, be introduced without the bore being lubricated. This is done by a composition of wax and grease being inserted between charge and shot, which at the same time tends to decrease whatever windage there may be left. The material of the gun is so tough that it will easily stand 3,000 rounds without any damage to the bore.

The Whitworth gun was brought before the public in February last, when a series of experiments were made with it at Southport, on the Lancashire coast. There were three guns—a 3-pounder, 12-pounder, and 80-pounder; from the long reports[h] we select the 12-pounder as an illustration. This gun was 7 feet 9 inches long, and weighed 8 cwt. The common 12-pounder, for round shot, is 6 feet 6 inches long, and weighs 18 cwt. The ranges obtained with Whitworth's gun were as follows: At 2 degrees elevation (where the old 12-pounder gives 1,000 yards), with a charge of 1¾ lb., the range varied from 1,208 to 1,281 yards. At 5 degrees (where the old 32-pounder gives 1,940 yards), it ranged from 2,298 to 2,342 yards. At 10 degrees (range of old 32-pounder, 2,800 yards), it averaged 4,000 yards. For higher elevations a 3-pounder gun was used, with 8 oz. charge; with 20 degrees, it ranged from 6,300 to 6,800, with 33 and 35 degrees, 9,400 to 9,700 yards. The old 56-pounder, of smooth bore, gives, at 20 degrees, a range of 4,381 yards, at 32 degrees, of 5,680 yards. The precision obtained by the Whitworth gun was very satisfactory, and at least as good as that of the Armstrong gun in lateral deflection; as to longitudinal variations, the experiments do not admit of a satisfactory conclusion.

[New-York Daily Tribune, No. 5950, May 19, 1860]

The Whitworth gun is constructed upon the principle of reducing windage to the utmost minimum, by a mathematical fit of the shot to the bore, and doing away with what little may remain by the effect of the lubricating composition. In this respect it is inferior to Armstrong's gun, which has no windage at all; and this we consider its principal defect. The polygonal bore, however, would be impossible without this defect, and at all events it deserves to be acknowledged that with such an originally defective system, such great results have been obtained. Whitworth has undoubtedly brought to its highest perfection the system which gives hard, unyielding shot and allows windage. His gun is immensely superior to the rough empiricism of the French rifled ordnance. But while Armstrong's gun, and other guns depending on soft-coated shot to be forced into the grooves by pressure, may be perfected ad infinitum, Whitworth's gun will have no such future; it has already attained the highest perfection compatible with its fundamental principles.

To recapitulate:

We find that at the practicable elevation of field-artillery, the best rifled guns known give a range but very little superior to the old smooth-bored gun. There is, however, some advantage, and this remains an item in their favor. But the great advantages of rifled ordnance for field-artillery are these:

1. The same weight of shot can be projected by a gun having a much smaller bore, and with a much smaller charge than with the old smooth-bored gun, which was only fit for spherical shot. Consequently, the weight of the gun is considerably reduced. The old 12-pounder had a bore of about 4½ inches, and weighed 18 cwt.; its charge was four pounds of powder. The new 12-pounder has a bore of about 3½ inches, or nearly that of the old 9-pounder; its weight, 8 cwt.; charge, from 1½ to 1¾ pounds. The French new 12-pounders, with the old 4-pounder's bore, are still lighter. This is an immense advantage. It gives to the field-gun a mobility hitherto unknown, and renders it almost as fit to go over any ground as infantry. More than four horses to a gun will henceforth be useless.

2. At the distances hitherto practicable for field-artillery, it gives a far greater chance of hitting; it lowers the trajectory, and reduces to a minimum both lateral and longitudinal deflections. At an exchange of round shot and shells with percussion fuses, a rifled battery will always beat a smooth-bored one of equal weight of shot.

As to heavy ordnance, it will be all-powerful against stone walls, especially by shell-practice with percussion fuses. This has already been proved by experiment, both in France and Germany. It will give ships and siege batteries a chance of bombarding towns at distances from 4,000 to 9,000 yards. In every other respect it will not alter materially the hitherto existing relations of besiegers and besieged, and of ships against batteries on shore.

On the other hand, the disadvantages of rifled ordnance are:

1. The common case-shot becomes either impossible or ineffective from the irregular line of flight imparted to the balls by the spiral rotation.

2. Firing with shell with time-fuses (and shrapnel shot with ditto) becomes almost impracticable, as the absence or reduction of windage prevents the flame of the explosion from communicating with the fuse which necessarily must be at the point of the oblong shot.

In spite of these drawbacks, rifled ordnance has now become a matter of necessity for every army. The question now is only, how these drawbacks can be obviated. That they will be so there can be no doubt. But it is certain that the same rules obtain in rifled ordnance which regulate the construction and use of rifled small arms. The exaggerated ideas of five-mile ranges in the one are as ridiculous as the notion of hitting a man with the new rifles at 800 or 1,000 yards; and still the advantages given by rifled bores in either case, are so great that it is imperative upon every army which may ever be called upon to fight with civilized foes, to do away with all smooth-bored barrels, both in small arms and artillery.

Notes