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ORDNANCE

that steel is now exclusively used in the manufacture of ordnance.

Classification. The various forms of modern ordnance are classified and named according to size and weight; kind of projectiles used and their velocities; angle of elevation at which they are fired; use; and mode of operation.

Guns.- Now_designated as "breech-loading rifles" (B. L. R.), to distinguish them from the obsolete smooth-bores and muzzle-loading rifles still in existence, are from 3 inches to 13 inches in calibre, from 12 to 39 feet in length, and from 1 to 70 tons in weight. They fire solid shot, or shells, weighing from 13 to 1,100 pounds, at high velocities (2,800 to 2,300 feet per second) and low elevation (about 12° max.). Their projectiles are capable of penetrating the best steel armor, from 2.3 to 19.4 inches__in thickness, at the distance of 2,000 yards. The terms, field, siege, and sea-coast guns, indicate no essential differences in the guns themselves, but prescribe limits of weight according to the required mobility. For field use about the most effective size is that of the 3.2-inch breechloading steel rifle; for siege purposes, that of the 5-inch siege mortars and guns; while the largest and heaviest types of ordnance are employed on the sea-coast fortifications.

Howitzers are shorter than guns of equal calibre, are fired at low velocities and higher angles, the maximum elevation being about 20°, Mortars are still shorter, are fired at still lower velocities and higher elevations, ranging from 45° to 60°. They are used to throw shells over intervening obstructions against objects and into camps unreachable by gun fire at low elevations.

Rapid-fire guns are those in which the operation of opening and closing the breech is performed by a single motion of a lever actuated by the hand. They are charged with fixed ammunition, the projectile, explosive, and primer being contained in a single metallic case, so that loading also is done by one motion, and differentiates them from that class of ordnance in which the projectile, explosive, and primer are inserted separately. Up to within a short time the term "rapid-fire,” in the United States, and "quick-fire," in England, implied similar qualifications, but now, in the United States Navy, a rapid-fire gun is officially defined as one in which a quick-working breech mechanism is operated by a single motion of a lever; in which fixed or separate ammunition may be used, but if the latter, prescribes a metallic case to hold the explosive; while a quick-fire gun is defined as one in which a quick-working breech mechanism is operated by one motion of a lever; is fitted with an automatic lock, and in loading uses a powder charge put up in a cartridge bag. These guns are made in various forms and are operated by several different systems of breech mechanism generally named after their respective inventors. Those best known are the Vickers-Maxim and the Armstrong, mostly used in England; the Canet, used in France and Russia; the Krupp in Germany; the Skoda and Krupp in Austria; the Bofors in the naval service of Norway and Sweden and of Denmark; while in the United States the Dashiel, Fletcher, Hotchkiss, Driggs-Schroeder, Maxim-Nordenfeldt, and Vickers-Maxim are used exclusively. The Nordenfeldt, one of the

first designed, is not much used by any country. Rapid-fire guns vary in size from 1-pounders to 13.5-inch rifles, and in speed of fire from 60 rounds per minute, in the Vickers-Maxim 1pounder, to I round in 2 minutes, in the 13.5inch B. L. R. The speed of the smaller guns depends upon the drill of the crew, while that of the larger guns depends practically upon the mechanism of the mount. The accompanying table gives the best speed of fire of modern guns of various calibres:

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The development of rapid-fire guns practically dates from 1881, at which time the British Admiralty called for a gun not to exceed 1,120 pounds in weight, and capable of propelling a 6-pound projectile with a muzzle velocity of 1,800 feet per second, to use fixed ammunition, and to be served by not more than three men. About the same time the French authorities called for a three-pounder to fulfil similar conditions. Hotchkiss, an American, living in France at that time, responded by producing a series of one-, three-, and six-pounders, while Nordenfeldt brought out similar guns in England. These guns were intended for use against torpedo boats, and the calibres chosen were considered sufficiently large for that purpose, as the torpedo boats at that date were weak and slow, but the advent of swifter and stronger torpedo boats and destroyers, with their coal arrangement practically amounting to a protective armor, caused an increase in calibre, and quick-working breech mechanisms were applied to guns of all sizes up to and including the six-inch breech-loading rifles. At this point fixed ammunition became unwieldy, necessitating the separation of the projectile from the powder charge. This condition, however, has not reduced the speed of the larger guns, as the ammunition thus separated is easier handled. In the effort to satisfy the requirement of increased speed of fire a new type of the VickersMaxim was introduced in 1897, in which a quick-working breech mechanism automatically ejects the primer and draws up the loading tray into positon as the breech is opened. This system was quickly applied to the new guns of the United States Navy and materially increased the speed of fire in all calibres. That of the five-inch guns was especially improved and to them the system will probably be applied universally, while it is safe to state that the general improvement in the breech mechanisms of all guns during the last five years has more than doubled their speed of fire. A comparative

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description of the Fletcher and Vickers-Maxim systems will be sufficient to give a general idea of these mechanisms. In the Fletcher, which is a development of the Farcot system, a wormwheel on a vertical spindle works on a rack attached to the breech plug. To operate, the slotted-screw breech plug is first rotated by a crank to disengage the threads, then moved rearward and turned clear out of the breech. It is probably the simplest and strongest of all breech mechanisms. In the Vickers-Maxim a short arm driven from the vertical axis of the operating lever shifts its centre during the motion. In the six-pounders and smaller guns the Hotchkiss breech-block, consisting of a vertically sliding wedge, and the Driggs-Schroeder mechanism, in which the block is dropped to clear it from the housings of the breech and then revolved to the rear around a horizontal axis, are practically the only systems used.

Machine Guns are rapid-fire guns in which the speed of fire is such that it is practically continuous. Attempts to construct multiple-firing guns may be traced back to the earlier part of the 17th century. Small guns of Chinese manufacture have been found bearing dates as early as 1607. They are necessarily of crude construction and consist of two parallel barrels re-inforced at the breech ends with three hoops each of which has a vent, showing that the piece is arranged to fire three shots successively out of each barrel. From the middle of the 17th century to the middle of the 19th century, frequent efforts were made to produce rapid-firing guns, but with indifferent success. The introduction of fixed ammunition about 1860, however, contributed greatly toward their successful construction. During the Civil War in the United States, a great many forms of magazine and repeating rifles, pistols, and machine guns of a more or less effective character, were quickly produced, of which the "Gatling gun" was by far the best. It was invented by Dr. R. J. Gatling of Indianapolis in 1860 and assured for machine guns a permanent place in armaments. Machine guns may be more precisely defined as those in which the operations of loading, firing, and extracting the empty cartridge shells, are wholly or in part accomplished by mechanism. They are of three classes: (1) those operated by hand-power, electric-motor, or any other form of exterior force; (2) the semi-automatic, in which, although the energy of recoil is partially used to actuate the breech mechanism, each round of ammunition is inscrted by the hand and the trigger is pressed for each discharge; (3) the automatic, in which the energy of recoil, or a part of the powder gas pressure at each discharge is fully utilized to operate the piece, which fires the rounds continuously while the trigger is pressed. To the first belong the Gatling and Gardner guns, the Nordenfeldt and the Hotchkiss revolving

cannon.

The Gatling gun consists of a number (usually 10) of parallel barrels grouped around and secured firmly to a main central shaft, to which is also attached the grooved cartridge carrier and the lock cylinder. Each barrel is provided with its own lock or firing mechanism, independent of the others, but all of them revolve simultaneously with the barrels, carrier, and the inner breech, when the gun is in operation.

The rotation of the gun gives a reciprocating motion to the locks, the forward and backward movement being effected by a cam actuated by the turning of the operating crank. In firing, one end of the feed case containing the cartridges is placed in the hopper on top and the operating crank turned. The cartridges drop one by one into the grooves of the carrier, and are loaded and fired by the forward motion of the locks, which also closes the breech, while the backward motion extracts and expels the empty shells. When first invented it was entirely different in principle and action from all other multiple-fire guns, admitting of faster discharges and heavier projectiles. It has passed through some stages of alteration and improvement, mainly in the arrangements for feeding the ammunition. At different elevations the original tin feed cases worked irregularly, so that the cartridges did not always fall into their proper positions in the grooves of the carrier, and jamming was of frequent occurrence. Various devices were designed to obviate this defect. The Bruce feed case, constructed on the gravity principle, overcame the defect of jamming, but not the irregularity of action at different angles of elevation, and was superseded by the Accles feed drum. This was a positive feeder, which rotating with the revolving barrels and lock cylinder, fed the cartridges with perfect regularity at any angle of elevation. It had, however, two serious drawbacks-its weight and the large amount of exposed surface, which if struck by a single bullet would at once put it out of action. In the latest method of feeding employed, the cartridges are attached to long strips of flexible metal and are fed into the openings in the hopper. As the gun is revolved by the operating crank, the projections in the grooves of the carrier act upon the cartridges and force the strips through the hopper, each cartridge being deposited in its proper position in the grooves of the carrier block and the empty strips thrown out to the right. In the latest forms an automatic traversing arrangement for scattering the bullets is attached, which can be thrown in or out of gear as may be desired, regulating the amplitude of the arc through which the breech is moved so as to spread the bullets over the required front. In its present state of efficiency the Gatling gun fires at the rate of 1,200 shots per minute, a speed of fire, by separate discharges, not as yet equaled by any other gun.

The Nordenfeldt, a contemporary of the Gatling, proved very efficient as a ship's gun. In it the barrels (usually 10) are placed horizontally side by side, and are immovable. Each barrel has its own firing mechanism, but all the locks, bolts, strikers, and spiral springs are contained in one box which is moved backward and forward by the operating lever. When the box is moved backward the cartridges fall out of the hopper on top and are deposited simultaneously in the grooves of the carrier. The forward motion of the box pushes them into the barrels, the cocking catches compress the spiral springs which are subsequently released by the lever in quick succession and produce a continuous fire. In this gun careful aiming from a moving platform is possible, so that at the right instant all the barrels may be fired at the object almost simultaneously, therefore its use

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fulness as a naval weapon. Its speed of fire is about 600 shots per minute.

The Gardner Gun closely resembles the Nordenfeldt. It consists of two or more barrels fixed immovably side by side in the same horizontal plane. The loading, firing, and extracting mechanism is moved backward and forward by a crank turned by the hand. Shortly after the appearance of the Gatling in the United States the "mitrailleuse" was produced in Belgium, and subsequently adopted by France. It consisted of several barrels (usually 25 or 37) arranged around a central shaft and covered with a metal casing. The barrels were loaded through the breech by the use of a metal disk pierced by holes to correspond with the number of barrels, a cartridge being held in each hole or chamber. In firing, this disk was placed against the breech end of the barrels, then the box containing the strikers was placed against it and all of the cartridges discharged at once. It was used to some extent in the Franco-German war of 1870, but was never very successful, and has been completely superseded by the Gatling and other types. The speed of fire of the Belgian gun was about 440 shots per minute, but that of the French piece rarely exceeded 300. The Gatling, Nordenfeldt, and Gardner guns, as also the various forms of mitrailleuse, were generally made in rifle calibre (.45-inch), but Gatlings of .65inch, and Nordenfeldts of 1-inch calibre, were constructed about the time the Hotchkiss onepounders were produced, in response to the cail of the English and the French authorities in 1887, for rapid-firing machine guns to be used against torpedo boats. The larger Gatlings and Nordenfeldts fire respectively about 200 and 100 shots per minute with sufficient velocity to penetrate the light iron plates generally used in the construction of torpedo boats. The five barrels of the Hotchkiss fire a total of 25 rounds per minute, but as its size has been increased up to the 6-pounders, which are capable of firing explosive shells or canister, its speed of fire has been relatively increased together with additional powers of penetration.

Semi-automatic Guns belonging to class 2 are represented by those of the Armstrong, Driggs, and Maxim-Nordenfeldt patterns, the last-named being the best known and the most effective. It has been adopted by the United States Navy to the exclusion of all other guns of the semiautomatic type, and is in fact the only gun of this character employed in the naval service of any country. Semi-automatic mechanisms are applied to guns too heavy to be operated by that of the ordinary machine gun. In them the recoil of the barrel is utilized as the actuating energy. The backward movement compresses the spring, which in turn pushes it forward again and forces the breech downward while the extractor throws out the empty cartridge case. In this position of the barrel the breech block is held open until a fresh cartridge is inserted which slides the extractors into the bore and allows the breech block to rise and close the breech, the gun being again ready to be fired. These mechanisms are most effectively used in guns of 2.24-inch and 3-inch calibre, giving them a speed of fire from 20 to 17 shots per minute, respectively.

Automatic Guns belonging to class 3 are the Hotchkiss, Colt, Yamanouchi (Japanese), and

the Maxim. They are made in rifle calibres and are operated by the pressure of the powder gas upon a level or piston when the piece is discharged. The larger types are the MaximNordenfeldt_one-pounder, called "pom-pom" in the British-Boer war of 1899-1902; the Skoda automatic gun, and the Dawson-Silverman threepounder. In these, excepting the last named, the recoil of the barrel or breech-block operates the mechanism. A description of the construction and operation of the Colt automatic gun will serve to give a general idea of those in which the pressure of the powder gas is used to actuate the mechanism. Near the muzzle the barrel is perforated radially by a small hole which is covered by a cylindrical lug attached to the front end of a vibrating lever pivoted on the gun. When the piece is discharged and the bullet passes the hole, the pressure of the powder gas in the barrel throws back the lug of the lever with enough force to reload and fire. The walls of the barrel are more than half of an inch in thickness, and it contains enough metal to prevent overheating without the use of a water jacket. The cartridges are attached to a bandolier or belt of woven cotton (250 to a belt), which is fed into the machine from a box at the side. The speed of fire is from 250 to 300 rounds per minute, so that when firing continuously a fresh belt of cartridges has to be placed in position every minute, but the consequent loss of time amounts to only a few seconds. For naval use those of .236- and 303-inch calibres, weighing about 42 pounds, are the most effective, generally being mounted on the ship's rail or on the rails of the fighting tops. A description of the Maxim 303-inch calibre automatic gun will be sufficient to explain the construction and operation of the type in which the recoil of the barrel is the actuating energy of the breech mechanism. It consists of a movable barrel and recoiling lock frame carrying a crank with a projecting arm and fusee to which a chain is attached. The fore end of a spiral spring is fixed to the nonrecoiling breech casing, its rear end being connected with the recoiling crank and fusee. When the piece is fired the barrel and lock move backward together about an inch, then the barrel is pushed forward again by springs and separated from the lock, leaving a space between them. This space is filled first by the extracted cartridge case and then by a fresh cartridge which is forced into the barrel and fired by the subsequent forward motion of the lock, actuated by the stored-up energy of the fusee spring. It is provided with a water jacket and fires from 300 to 350 rounds per minute. In the field machine guns are used to deliver a destructive fire along a wide front, or a concentrated fire into massed troops. In the former case the traversing gear is employed, while in the latter the barrels are fired in a stationary position. The relative efficiency of the rifle calibres and the larger automatic guns may be more clearly understood by comparing a .303-inch gun, which fires about 350 bullets per minute and has a maximum range of 2,500 yards, with a 15pounder, which fires six rounds of shrapnel shells per minute, and has a range of 6,000 yards. As each shrapnel shell contains 212 bullets the number of bullets delivered at the target amounts to 1,272 per minute. As naval

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weapons, machine guns of small calibre are the most efficient. Mounted on light draft vessels they are very useful in close-range operations on rivers and on the waters of narrow harbors, while as boat guns they render efficient service to drive off the enemy preparatory to the landing of troops, or to cover their reembarkation. The efficiency of the larger calibres, however, is more questionable. The effect of the bursting of a one-pounder shell against the unarmored side of a cruiser, much less against the heavy armor of a battleship, is absolutely nothing; while against modern torpedo boats even the six-pounders are quite ineffective. Probably the best weapons for use against torpedo boats are rapid fire guns of about 3 to 4-inch calibre, throwing shrapnel shells, and capable of being carefully aimed. The impression that the projectiles discharged from a machine gun of any type can be directed like the jet from a hydraulic hose is absurd. The jump and jerk of recoil of the guns of even the smallest calibre is so powerful that good aim is out of the question at any range. On this account the larger machine

32-Pounder Carronade (1800).

guns are so constructed that they can fire single shots whenever desired a capability which probably defines their most efficient use.

The organization of machine gun details and the method of their employment as attachments to regiments of cavalry and infantry, differ in the various countries. The lessons taught by their use in the Franco-German war, or in the operations of the British in their Egyptian and Indian campaigns, are quite inconsequential. The British-Boer war afforded an opportunity for the use of every form of modern machine guns, but under conditions unfavorable for a determination of their use in the future. That the noise of the "pom-poms" exerted a demoralizing effect greater than that of bursting shrapnel shells is undoubtedly a fact, and, although the "moral effect of gun-fire" is one of the important problems of military science, it is hardly worth more than an incidental mention in this connection. One fact, however, is clear, on account of their great mobility they will be advantageously employed in the future as auxiliaries to the regular field batteries, which they never can be expected to supersede.

The manufacture of ordnance requires the solution of a great many scientific and practical problems involving the adaptations of means to ends, and the exactitude of the adaptations increases with the increase in the size of the guns and their required greater efficiency.

So complex a subject is more conveniently treated by grouping the various operations into

a number of general classes, as follows: Requirements for Efficiency; Principles of Design; Materials and Methods of Construction; Rifling; Systems of Loading; and Carriage and Mounts.

Requirements for Efficiency are, safety, accuracy of fire, destructive effect of projectile, and speed of fire. To these may be added that of mobility, especially applicable to field ordnance.

Principles of Design.-In designing a gun as an engineering structure, two distinct sets of conditions have to be considered-those regulating its proportions, influenced by the character of its intended use-and those pertaining to its mechanical construction, to withstand the strains it may be subjected to under the requirements for efficiency.

The three principal strains that a gun has to withstand are, (1) a circumferential tension caused by the outward pressure of the powder gas, acting radially with a tendency to enlarge the bore and split the gun open longitudinally; (2) a longitudinal strain having a tendency to stretch the gun or pull it apart in the direction of its length; and (3) a transverse strain caused by the weight of the parts of the gun overhanging beyond the point of support; all of which are brought into action the instant the gun is fired. The calibre of the gun having been determined, together with the conditions of loading the weight of the projectile and the powder charge necessary to give it the required velocity; the pressure that will be exerted on the surface of the bore is determined by calculating its amount at a certain number of given points and a "pressure curve" plotted. Such a curve shows that the maximum pressure is exerted before the projectile has moved more than a few inches, and decreases rapidly as it approaches the muzzle. With the pressure as a known factor in the problem, the material having a tensile strength sufficient to sustain the forces that will be exerted is selected, and methods of construction determined, to dispose it economically and safely, consistent with the production of the desired ballistic results.

Materials and Methods of Construction.-In the development of ordnance increasing pressures compelled the employment of materials of greater and greater tensile strength and higher elastic limits. Wooden bars held together with iron hoops gave way to cast-iron, which in turn was superseded by bronze, brass, wroughtiron, and steel, until finally the pressures exceeded the inherent strengths of the materials and forced the adoption of methods of construction by which additional powers of resistance were derived from the arrangement of the material. In hollow cast-metal guns there is a limit beyond which increase in thickness does not give additional strength to resist bursting pressure. If the metal employed was incompressible, the resistance to the pressure by each concentric layer of the metal would be inversely proportional to the square of its distance from the axis of the bore. But as all metals possess not only the quality of compressibility, but that of extensibility as well, the interior layers are supported by those on the outside to a very great degree. Therefore the great object in construction is to so arrange the material that the exterior layers will take up as much as possible

[graphic]

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of the pressure exerted upon the interior layers. Dahlgren first suggested the construction of guns in which the disposition of the materials was in accordance with the data obtained from the curve of pressures, while Rodman introduced the principle of initial tension. In the construction of modern built-up guns these principles are carried into effect as follows: An ingot of "low steel" is cast and allowed to cool slowly to avoid strains. It is then bored in a lathe, reheated, and forged on a mandrel. Consequent strains are removed by annealing, and the forged tube is turned and bored in a lathe to about the required size. After being oil-tempered, to give toughness, and re-annealed to remove strains induced by the tempering, it is re-bored in a lathe and smoothed by a reamer. In the meantime different parts of the outside of the tube are turned to sizes slightly exceeding the calculated shrinkages of the hoops intended to encircle them. This difference is about three tenthousandths of the corresponding diameters, the shrinkages being so calculated that under no circumstances will any portion of the metal be strained beyond its elastic limit. Jackets and hoops are constructed in a similar manner and the various parts assembled into a complete gun. In the operation of assembling the tube is placed

allows the projectile to rebound along the sides of the bore as it is driven forward, the direction of its departure from the muzzle being that of the last bound, instead of that of the axis of the bore; while the lack of exact sphericity in the shape of the projectile causes an unequal pressure of the air on the different parts of its surface, still farther deflecting it from the aimed direction. Accuracy of manufacture can reduce these errors, but cannot remove them entirely. Therefore by rifling the bore the projectile is caused to rotate around its own axis, which is coincident with that of the bore. Thus, the errors due to windage are completely eliminated and the effects of unequal air pressure are neutralized. Rifling is effected by furrowing the surface of the bore with a series of spiral grooves of uniform or increasing twist. The number of grooves and the amount of twist depends upon the calibre and length of the gun, the required muzzle velocity of the projectile, the length of the projectile, and the velocity of rotation necessary to keep it point-first while being driven through the air. The earlier muzzle-loading guns were rifled with grooves of a uniform twist, and the projectile was provided with ribs or studs which fitted into the grooves and caused it to rotate while being

6-inch Gun (1883).

in a vertical position in a pit; the hoop or jacket to be put on is subjected to a temperature of about 700° F., and its diameter expanded to a size about .06 inch greater than that of the part it is intended to surround. In this condition it is lowered over the tube until it rests upon the shoulder which fixes its position. It is then cooled. The water is first poured on and around it near the shoulder (to prevent the jacket drawing away from the shoulder when it cools), then progressively upward, over the entire hoop. The gun is then put on the lathe and its surface turned preparatory to the shrinking on of the next hoop, the operation being repeated until all the hoops are in place, including the trunnion hoop, onto which the trunnions are forged solid. The gun is then finish-bored to the required calibre, turned to the specified form and rifled.

Rifling. When a spherical projectile is fired from a smooth-bore gun, the probability of its following the direction corresponding to the aim is very small. The tendency of such a projectile to follow the mean trajectory (path of flight) depends upon the amount of "windage" (the difference between the diameter of the bore and that of the projectile), and the exact sphericity of the projectile. Large windage is the principal cause of error, since it

driven forward. As the size of the guns increased the greater strain of imparting rotation at starting tended to force out the studs and wear away the driving edges of the grooves. The casting-on of ribs was found to be impracticable on account of difficulties of manufacture, and all attempts to use expanding projectiles were unsuccessful. Therefore the system of increasing-twist, based upon the principle of the semi-cubical parabola, was devised and practically met all the requirements of the case. Studded projectiles were replaced by those with copper bands fitted around the base. These bands being slightly larger than the bore were forced into the rifling grooves and not only gave rotation to the projectile as it was driven toward the muzzle, but by cutting off all the windage acted as an effectual gas-check. The various systems of rifling, designated "single-groove," "double-groove," or "polygroove," according to the number of grooves employed, are here stated in the chronological order of their development and adoption, but the last-named is the one now used, exclusively.

For example-the guns of the United States Navy are rifled under a poly-groove system in which the twist increases from o to I turn in 25 calibres. The grooves start parallel to the axis of the bore, but quickly incline to the form

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