Albert G. Hadcock, Henry A. Bethell, Julian R. J. Jocelyn & Sydney R. Fremantle

“ In most English machines the cutting tool cuts only as the rifling bar is drawn out of the gun; during the reverse motion the cutter F is withdrawn out of action by means of a wedge arrangement actuated by a rod passing through the centre of the rifling bar, which also pushes forward the cutter at the proper time for cutting. One, two or more grooves may be cut at one time, the full depth being attained by slowly feeding the tool after each stroke. After each set of grooves is cut the rifling bar or the gun is rotated so as to bring the cutters to a new position. ”

“ The first to employ successfully this important principle for all parts of a gun was Lord Armstrong (q.v.) , who in 1855–1856 produced a breech-loading field gun with a steel barrel strengthened by wrought iron hoops. In this system (fig. 11) wrought iron coils were shrunk over one another so that the inner tube, or barrel, was placed in a state of compression and the outer portions in a state of tension—the parts so proportioned that each performs its maximum duty in resisting the pressure from within. ”

“ Metallurgical science had made great progress, but cast iron was still the only metal considered suitable for large guns, whilst bronze was used for field guns. Many accidents, due to defects developing during practice, had, however, occurred, in order to prevent which experimental guns constructed of stronger material such as forged iron and steel had been made. Some of these weapons were merely massive solid blocks, with a hole bored in for the bore, and only withstood a few rounds before bursting. ”

“ In order to obtain additional longitudinal strength the outer tubes are so arranged that each hooks on to its neighbour from muzzle to breech. Thus, the chase hoop hooks on to the barrel by a step, and the succeeding hoops hook on to each other until the jacket is reached which is then secured to the breech piece by a strong screwed ring. In all the latest patterns of English guns there is a single chase hoop covering the forward portion of the gun and a jacket covering the breech portion, an arrangement which simplifies the design but increases the difficulties of manufacture. ”

“ The gun can, however, be arranged to withstand a considerably higher working pressure by building it up on the principle of initial tensions. The inner layers of the metal are thereby compressed so that the gas pressure has first to reverse this compression and then to extend the metal. The gun barrel supported by the contraction of the outer hoops will then be able to endure a gas pressure which can be expressed as being proportional to the initial compression plus the extension, whereas in the old type solid gun it was proportional to the extension only. ”

“ The barrel or hoop A, to be bored, is passed through the revolving headstock B and firmly held by jaws C, the other end being supported on rollers D. A head E, mounted on the end of a boring bar F, is drawn gradually through the barrel, as it revolves, by the leading screw K actuated by the gear G. The boring head is provided with two or more cutting tools, and also with a number of brass pins or pieces of hard wood to act as guides, in order to keep the boring head central after it has entered the barrel. ”

“ A stronger material than ordinary carbon gun steel was consequently demanded from the steel-makers, in order to keep the weights of the heavier natures of guns within reasonable limits. The demand was met by the introduction of a gun steel having about 4% of nickel in addition to about 0·4% of carbon. This alloy gives great toughness and endurance under a suitable oil hardening and annealing process, the yielding stress being about 26 tons to 28 tons and the breaking stress from 45 tons to 55 tons per square inch, with an elongation of 16%. ”

“ The gun (fig. 10) had a removable breech block having on its front face a coned copper ring which fitted into a coned seating at the breech end of the powder chamber. The breech block was secured by means of a powerful breech screw; a hole was made through the screw so that, in loading, the shell and cartridge could be passed through it after the breech block had been removed. After loading, the block was dropped into its place and the breech screw turned rapidly so that it might jam the block against its seating, and so prevent the escape of powder gas when the gun was fired. ”

“ The maximum rotating pressure, with uniform rifling, is certainly somewhat higher, but not to a very great extent, and as it occurs when the projectile is still moving slowly, the wear due to friction will be correspondingly low; the pressure gradually falls until the muzzle is reached, where it is much lower than with increasing rifling. The projectile thus leaves the gun without any great disturbance from the rifling pressure. ”

“ The American, Dr Woodbridge, claims to have originated the system of strengthening guns by wire in 1850; Brunel, the great railway engineer, also had similar plans; to Longridge, however, belongs the credit of pointing out the proper mode of winding on the wire with initial tension so adjusted as to make the firing tension (i.e. the tension which exists when the gun is fired) of the wire uniform for the maximum proof powder pressure. Great success attended the early introduction of the coil system. Large numbers (about 3500) of breech-loading Armstrong guns from 2·5 in. ”

“ With wire guns the procedure is somewhat different. The wire is wound on to its tube, which has been previously fine turned; the exterior diameter of the wire is then carefully measured and the interior of the covering tube or hoop finished to suit. The covering hoop is allowed usually only a small shrinkage, or sometimes none, as it is simply intended as a protection to the wire and to give longitudinal strength; but in order to place it over the wire it must be heated and thus some little contraction always does take place on cooling. ”

“ Thus, any erosion of the straight part of the rifling would not affect that portion giving rotation, and it was argued that the gun would remain efficient for a longer period. The defect in this system is that when the projectile arrives at the end of the straight rifling it has a considerable forward velocity and no rotation. Rotation is then imparted by the increasing twist of rifling, and the resulting pressure on the engraved ribs of the driving band rises suddenly to a maximum which, in high velocity guns, the driving band is unable to resist. ”

“ Up to about 1850 the dimensions of canon had been proportioned by means of empirical rules, as the real principles underlying the construction of ordnance had been little understood. It was known of course that a gun was subjected to two fundamental stresses—a circumferential tension tending to split the gun open longitudinally, and Built-up guns. a longitudinal tension tending to pull the gun apart lengthwise; the longitudinal strength of a gun is usually greatly in excess of any requirements. ”

“ Most variety exists in the expansion type, where the pressure of the powder gas acts on the base of the projectile or on the driving ring and compresses a lead, copper or asbestos ring into the rifling grooves. ”

“ Many ingenious devices for giving rotation and preventing the escape of gas past the projectile were tried in the early days of modern rifling. Experiments of this nature still continue to be made with a view to improving the shooting and to prevent the erosion of the bore of the gun. ”

“ Their view is that movements—such as stretching of the inner parts—are bound to take place under the huge forces acting upon the tubes, and that it is better to allow freedom for these to take place naturally rather than to make any attempt to retard them.On the other hand it cannot be denied that the rigid construction is conducive to strength and durability, but it is essential that massive tubes of the highest quality of steel should be employed. ”

“ After the projectile and charge had been loaded into the gun through the breech, a cast iron cylindrical plug, cupped on the front face, was introduced into the chamber; a copper ring was placed against its rear face; finally a strong iron wedge was passed through the body of the gun horizontally just in rear of the plug, and prevented it being blown out of the gun. In England the breech of one of the experimental guns was blown off after only a few rounds had been fired. In Wahrendorff’s gun, invented in 1846, the breech arrangement (fig. 9) was very similar in principle to the Cavalli gun. ”

“ In addition, the use of a copper driving band ensures a uniform resistance while this is being engraved and the projectile forced through the gun, and also prevents the escape of gas. These elements have a very great influence on the accuracy of the shooting, and fully account for the vastly superior results obtained from breech-loading ordnance when compared with the muzzle-loading type. Driving bands of other materials such as cupro-nickel and ferro-nickel have also been tried. ”

“ On the other hand, the development of the gun has always had an upward tendency, which of late years has been very marked; the demand for the increase of energy has kept pace with—or rather in recent times may be said to have caused—improvements in metallurgical science.
The evolution of ordnance may be divided roughly into three epochs. The first includes that period during which stone shot were principally employed ”

“ It is by no means certain when wheeled carriages were introduced. They must have gradually appeared as a means of surmounting the difficulties engendered by the recoil of the piece and of transport of the early guns and their cradles. Andrea Redusio mentions in Chronicon Tarvisinum the use of two wheeled bombard carriages at the siege of Quero by the Venetians in 1376. It does not follow that these weapons were of large dimensions, as the term “bombard” was applied to small guns as well as to the more ponderous types. ”

“ Kotter (1520) and Danner (1552) , both of Nuremberg, are respectively credited as being the first to rifle gun barrels; and there is at the Rotunda, Woolwich, a muzzle-loading barrel dated 1547 rifled with six fine grooves. At this early period, rifling was applied only to small arms, usually for sporting purposes. The disadvantage of having, during loading, to force a soft lead (or lead-covered) ball down a bore of smaller diameter prevented its general employment for military use. ”

“ It will thus be seen that although an increasing twist of rifling may be so arranged as to give uniform pressure, it is evident that if wear takes place, the engraved rib becomes weaker to resist shearing as the shot advances, and the rate of wear also increases owing to the increase of heat by friction. ”

“ Many authorities believe that the best results are obtained when the projectile is fitted with two bands, one near the head and the other near the base, and no doubt it is better centred when so arranged, but such shot can only be fired from guns rifled with a uniform twist, and it must also not be forgotten that the groove formed for the front band in the head of the projectile necessarily weakens that part of the projectile which should be strongest. ”

“ Now, the moral effect may be considered more or less constant, for, as men are educated to the presence of artillery, the range of guns, their accuracy, mobility and on shore their invisibility, so increase that there is always the ever present fear that the stroke will fall without giving any evidence of whence it came. ”

“ It is found that the quality of the steel is greatly improved by forging, so long as this is not carried so far as to set up a laminar structure in the metal, which is thereby rendered less suitable for gun construction—being weaker across the laminae than in the other directions. ”

“ It will be seen that the wire is extremely strong and the moderate stress of from 35 to 50 tons per square inch, which at most it is called upon to withstand in a gun, is far less than what it could endure with perfect safety. ”

“ Wire guns are now made of almost all calibres, ranging from 3 in. to 12 in. Many authorities objected to guns of less calibre than 4·7 in. being wound with wire, as they considered that on diameters so small the interior surface of each layer of wire is over-compressed, while the exterior is too much extended; but by proportioning the thickness of the wire to the diameter of the tube on which it is wound there is no reason for this to be so. ”

“ By rotating the gun the wire is drawn off from the drum against the resistance of the band brake, which is so designed that, by adjusting the weight S suspended from the brake strap, any desired resistance can be given in order to produce the necessary tension in the wire as it is being wound on the gun. The stress on the wire is indicated on a dial, and the headstock, containing the drum of wire, is capable of being moved along the bed G by a leading screw H, driven by a belt through variable speed cones I ”

“ Trunnion bearings were cut in the upper surface of the cheeks over the axletree, and these were lined with iron, while the trunnions were secured in position by iron cap-squares. Elevation was given by a wedge or “quoin” being placed under the breech and supported by a transom or stool bed. For transport the trail end of the carriage was supported on a limber, a pintle on the limber body passing through a hole in the trail. One set of shafts were fixed to the limber, and a single horse was harnessed to them ”

“ The top of the ingot is generally porous, and consequently, after cooling, it is usual for about one-third of the length of the ingot to be cut from the top and remelted; a small part of the bottom is also often discarded. ”