Read Ebook: Field artillery materiel by Kelly James P James Patrick Compiler

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The use of Greek fire was understood as early as the sixth century, but powder was earliest used in China, perhaps a thousand years before Christ, and was introduced to European notice by the Saracens.

From the discovery of gunpowder by the English monk Bacon in 1248, sixty-five years elapsed before a Franciscan monk produced the first gun in Germany, about 1313. The first guns were of a small breech-loading type, supported in front by crossed sticks and anchored by a spike at the breech. Later these guns were fastened to cradles, the latter being mounted on sleighs, and finally, in 1376, the Venetians produced the first wheel mounts, which had become common by 1453, when the Turks took Constantinople.

The ancient carriages were remarkable because of the fact that in general design they embodied the same principals which are included in the field carriages of to-day. One example from the fifteenth century shows a breech-loading gun mounted in a cradle supported by trunnions on the forward extension of the trail over the axle. The cradle was elevated by a pin-and-arc arrangement, supported on the trail. The axle supported by wheels passes through the trail to the rear of and below the cradle trunnion support and in front of the point of attachment of the elevating arc.

Field guns fell into disuse about 1525 with the introduction of musketry, and remained so until 1631, when Gustavus Adolphus gave artillery its true position on the battlefield.

Swedish artillery reigned supreme in the early part of the seventeenth century. Gustavus introduced marked changes by making the guns and the carriages lighter and handier, and by adapting their movements to those of the other arms and to the requirements of the battlefield. In this, as in all his military efforts, his motto was mobility and rapidity of fire.

In 1624 Gustavus had all his old types of guns recast into newer models and the following year he himself contrived a gun which three men and one horse could maneuvre to good effect. It was an iron three and four pounder with a cartridge weighing less than a pound and consisting of a charge held in a thin wooden case wired to a ball. This was the first artillery cartridge, the original fixed ammunition. The gun was afterwards used in other European armies and known as the "piece Suedoise." Not only had it the advantage of lesser weight but its cartridge was always ready to fire and it could be fired eight times to the six times of the infantry musket of that day.

In the wars against the Poles, Gustavus employed with profit the so-called leather cannon, a fact which shows how lacking the times were in artillery power. These guns were invented in the early 1620s by a Colonel Wurmbrandt, and consisted of a thin copper tube reinforced by iron bands and rings, then bound with rope set in cement, the whole covered with sole leather. The tube was made to screw in and out because it grew heated by from eight to twelve charges and had to be cooled. The gun carriage was made of two planks of oak. The gun without the carriage weighed about ninety pounds and was fired with a light charge. They were used during 1628-29 and then gave way for four pounder cast-iron guns which remained in common usage in Europe until artillery was reorganized by Frederick.

Gustavus' batteries excited universal admiration. Grape and canister were generally employed in the field guns and round shot only in the siege guns. Artillery was used massed or in groups and also with regiments of foot soldiers. Gustavus was probably the first to demonstrate the real capabilities of artillery.

Mortars throwing bombs were first used at the siege of Lamotte in 1634. Hand grenades, shells, fire-balls, etc., came into more general use as the German chemists made their new discoveries. Artillery practice grew to be something of a science; experts took it up and the troops were better instructed. Regimental artillery, that is, artillery with the infantry, was attended by grenadiers detailed for the work. There were special companies for serving the reserve guns.

Artillery ceased to be a guild of cannoneers as it long had been and became an inherent part of the army. More intelligence was devoted to it and more money spent on this arm of the service; it grew in strength and importance, and was markedly improved. But while the artillery service ceased to be a mere trade, it did not put on the dignity of a separate arm, nor was the artillery of any great utility in the field until well along in the eighteenth century. Guns, however, in imitation of the Swedes, were lightened, particularly so in France; powder was gradually compounded on better recipes; gun-metal was improved; paper and linen cartridges were introduced; gun carriages were provided with an aiming wedge; and many new styles of guns and mortars, and ammunition for them were invented.

Although sensibly improved, the artillery was far from being skillfully managed and was slow firing; it usually stood in small bodies all along the line of battle. It was heavy and hard to handle and haul, principally because the same guns were used for both siege and field work, and was far from being, even relatively to the other arms, the weapon which it is to-day.

In 1765 General Gribeauval of France introduced artillery improvements, especially in the carriages, and formed a distinct artillery service for the field which was lighter than the old service and was drawn by teams which were harnessed double as they are to-day.

Howitzers were introduced in France in 1749. The weapons were given an early sort of perfection by the Dutch. The term "howitzer" comes from the German "haubitz." In 1808 the first shrapnel appeared at Vimera. It was invented by an English colonel by the name of Shrapnel. At the time it was known as case shot. The type employed by Napoleon, had a fuze that could be used at two different ranges. The French still have this type in their armament.

Field artillery now began to appear in the form which it was to retain with but a few changes, until the era of the modern field carriage. The cradle disappeared, muzzle-loading guns cast with trunnions taking its place, and a stepped wedge resting on the trail superseded the pin and arc. With the exception of the gun, most parts of these carriages were of wood and were to remain so until 1870, when metal carriages came into general use. Muzzle loading guns had supplanted breech-loaders because of the poor obturation and the many accidents resulting from use of the latter type. Although numerous experiments were made, breech-loading guns did not come into vogue again until 1850, when the experiments of Major Cavalli , the Walnendorff gun and the Armstrong gun , produced satisfactory types.

Up to 1860 practically all guns were smooth bore. Even during the Civil War the smooth bore was generally used, although the rifled gun began to make an appearance and was used in small numbers by both sides at the battle of Gettysburg. Some breech loaders began to appear at the same time. Improvement in the ballistic properties of the gun necessitated a corresponding improvement in the sighting facilities. In 1880 rifled breech loading and built-up steel cannon came into general use. Rifled guns shoot accurately and as a result, improved methods in direct laying were devised.

The period between from 1880 to the present, has brought about changes in gun construction which, possibly, have been equaled in importance to artillery only by the present change which is taking place in the means of artillery transportation and self-propelling mounts. In this period in rapid succession came the modern breechblock and with it the rapid firing gun. This brought about the change to the present system of breaking the force of recoil of the gun and restoring it to its firing position without disturbing the position of the carriage. This added to the possibilities of rapid and more accurate fire. Then came the invention and use in the field artillery of smokeless powder. Previous to this time the great amount of smoke produced by the black powder when the piece was fired retarded the rapidity of fire because it enveloped the materiel in a thick cloud of smoke which obscured the target and made it impossible to fire again until the smoke had blown away. It made concealed positions for the artillery almost impossible. The advent of smokeless powder made firing more rapid and made possible the selection of concealed positions. This in turn made indirect fire feasible and necessitated the development of better sights. Indirect fire increased the rapidity of fire and gave to the commanders of firing units a greater control over their fire. With the use of recoil mechanisms and shields for the guns, the cannoneers were permitted to serve the piece continuously--a condition which was impossible with the recoiling carriage. The shields made it almost impossible to put the gun out of action unless some vital part of the mechanism was destroyed.

The first of the modern carriages which were produced in the early nineties should be classified as semi-rapid carriages, as the recoil brakes were so abrupt that the carriage was not stable and jumped considerably, gaining for the type the sobriquet of "grass-hopper guns."

In 1897 the immortal French "75" was born, the pioneer of all modern quick-firing field guns, which still maintains its superiority in many respects over later designs.

In 1902 our own 3-inch field gun was produced and still finds favor among many of our field artillery officers, even over the French "75."

The Deport carriage brought to this country from Italy, in 1912, introduced to us the split trail, high angle of fire, wide traversing type of field gun carriage. This carriage was extensively tested by the Ordnance Department; by the Field Artillery Board at Fort Riley, Kansas; and by the School of Fire for Field Artillery, at Fort Sill, Oklahoma. The Field Artillery Board unqualifiedly approved of the Deport carriage and recommended that it be adopted. The School of Fire for Field Artillery also approved of this type.

In 1916 the United States produced a 75-mm field gun which featured a split trail with an elevation of 57 degrees which permits its use as an anti-aircraft weapon and a variable length of recoil which prevents the breech from hitting the ground at the extreme elevations. It has a traverse of 800 mils in comparison to the 106 of the French 75 and the 142 and 140 of the British 75 and American three-inch field gun.

The outbreak of the late war saw all modern armies largely equipped with guns resembling the French "75" in a long-run recoil mechanism, weight of projectile and weight of carriage, etc. The fact that the largest number of horses which could best be handled to maneuver the light guns--about 6--could not pull over a long period a gun or caisson with its limber if the weight was more than about 4500 pounds, resulted in the practical standardization of light guns in all armies. So in 1914 we see that time and development had given light gun perfection and mastery of artillery technique to the French while the Germans, probably, possessed the most efficient artillery program. The German types of weapons were more varied and perhaps better suited to the varying artillery needs in rendering that assistance to the infantry for which the artillery exists.

In our service during the World War, French 75s and the 155-mm Howitzer were used as divisional artillery. Two regiments of the light guns and one regiment of 155-Howitzers were assigned to each infantry division. As the war progressed guns and howitzers ranging from the 4.7" rifle, up to, and including 14 and even 16-inch naval guns on railroad mounts, were used as Corps and Army artillery.

Thus artillery development has gone steadily forward. Every military power has striven with the aid of its best engineers, designers and manufacturers to get a stronger gun, either with or without a heavier projectile, but in every case striving for greater power. As a special development and a not too important one, due to its lack of effectiveness in comparison to its cost, we find the now famous long range gun of the Germans, successfully delivered a projectile approximately 9 inches in diameter into Paris punctually every twenty minutes from a point about 75 miles distant. The Germans used three of these guns in shelling Paris. Their life was probably limited to about 75 rounds due to the excessive demands made upon the materiel.

The American Field Artillery Service now has before it four types of field gun carriages, namely our 3" model of 1902; the French 75 M-1897; the British 18 pounder, M-1905 converted to a 75-mm ; and our 75-mm model, 1916. There is being produced an improved model of 1916 75-mm carriage on which the St. Chamond pneumatic recuperator, adopted jointly by the American and French governments, will be substituted for the spring recuperators; and the French 75-mm gun will be substituted for our shorter calibered type. From these types one must be selected. An intelligent selection involves a consideration of what may be expected in the future in order that it may best fit in with the new types yet to be evolved.

For horsed artillery--and horse artillery will be with us for some years to come--the limiting features of draft and man power will still pertain.

For tractor-drawn mobile artillery, the limiting feature is the tractive power of the tractor with relation to the weight of the gun and carriage, the unit being physically limited in weight by the supporting-power of the pontoon bridge which is about 10,000 pounds per vehicle.

In conclusion it might be said that one of the greatest changes which has ever taken place in the development of field artillery is now underway in the form of motorization. Prior to 1917 horse traction had been the sole means of transporting mobile field artillery. The limit of the capabilities of horse traction placed a weight limit upon gun construction and to some extent upon artillery tactics. The increase in the ratio of field artillery to infantry, the corresponding demand for artillery types of horses and the decrease in the availability of the latter as the war continued, combined with the great improvements which were constantly being wrought in mechanical transportation as the war lengthened, opened the way for artillery motorization.

The French began by placing their 75s on trucks for rapid changes of position. All the armies saw the possible advantages to be gained from the use of trucks with artillery but none planned--nor have any since put into practice--the extensive use of trucks, caterpillar tractors and motor transportation for personnel, which the United States planned on her entrance into the war. It was planned to equip about one-third of the A. E. F. artillery regiments with complete motor equipment. This plan did not entirely materialize but after the armistice the 3rd Field Artillery Brigade of the 3rd Division was completely motorized and its practice marches in Germany were most successful and full of promise for the future. To date the motorization of all our mobile Field Artillery, with the exception of about fifty per cent of the light field guns, has been authorized.

Motor traction gives a better performance than animal. While the latter, especially with the light field guns, possesses great mobility, it is not a sustained nor a persistent mobility; it is more easily exhausted and requires longer to recuperate. These are points of vital importance from a military viewpoint.

In 1920 a self-propelling caterpillar mounted with a 75-mm gun, model 1916, was tested with a view to ascertaining the ability of the motor to function in water, i. e. fording streams, etc. The caterpillar successfully moved through ice water which completely submerged the carburetor.

Passenger cars for the transportation of personnel, four wheel drive trucks with caterpillar tractors for the transportation of the materiel, and the development of self-propelling mounts for the 75 and 155 rifles are the latest and the most important developments in field artillery materiel.

ELEMENTS OF GUN CONSTRUCTION AND DESIGN

"A gun is a machine by which the force of expanding gas is utilized for the purpose of propelling a projectile in a definite direction." It is essentially a metal tube closed at one end, of sufficient strength to resist the pressure of the gases caused by the combustion of the powder charge in the confined space at the closed end of the tube behind the projectile. The rapid combustion of the powder, which produces a high temperature, gives rise to a pressure uniformly exerted in all directions within the confined space. The energy exerted is used in forcing the projectile from the tube.

TUBES

Due to the effort of the large amount of superheated gas generated, which tends to expand in all directions, tremendous rending stresses are set up in the tube. Formerly these stresses were met by a sheer mass of metal, but, as the size of the projectiles increased and the necessary pressure to give them muzzle velocity increased, the size of the guns increased beyond the practical limits of mobility. This was at first offset by forgings of refined alloyed steels, but even these failed to keep pace with the increasing pressure desired. The new condition was met by the introduction of the "built-up" and the "wire-wrapped" guns. The modern built-up gun is made by assembling one or more superimposed cylinders around a central tube. The superimposed cylinders, whose inside dimensions are slightly smaller than the outside dimensions of those on which they are to be assembled, are expanded by heat sufficiently to allow them to be assembled over the tube. The subsequent contraction on cooling causes each of them to exert a uniform pressure on the cylinder immediately underneath. This method of assembling is called "shrinkage." This gives a compression to the inner tube and a slight tension to the outer one. The compression is so much additional strength to the tube because it must first be overcome before the powder gases can exert a tension on the inner tube fibers. The exact amount of the compression and tension for all parts of a gun at rest or resisting an explosion is a matter of mathematical calculation. The built-up construction has been used in practically all our present day types of field artillery.

THE WIRE-WRAPPED GUN.

Wire-wrapped guns consist of:

An inner steel tube which forms a support on which the wire is wrapped and in which the rifling grooves are cut.

Layers of wire wrapped upon the tube to increase its resistance by the application of an exterior pressure as well as to add to the strength of the structure by their own resistance to extension under fire.

One or more layers consisting of a steel jacket and hoops placed over the wire with or without shrinkage. The jacket generally furnishes longitudinal strength to the guns, and the breech block is screwed into the jacket, or into a breech bushing, which is screwed into the jacket.

The principal advantages of this type of gun over the built-up is economy of manufacture and greater facilities for inspection of materiel in the layers over the tube. The wire wrapping has itself a large reserve of strength due to the high elastic limits that may be given it. Two methods are used to wrap the wire: at constant tension at varying tension so that when the gun is fired with the prescribed pressure, all layers of wire shall be subjected to the same tangential stress. The latter method is theoretically better, but because of the ease of manufacture, together with the large factor of safety possible, the wire is usually wrapped at a constant pressure.

THE BUILT-UP GUN.

All army guns except small howitzers or mortars are of the built-up or wire-wrapped type. Built up guns of less than 5" caliber, or howitzers up to 8" caliber consist of an inner tube and a jacket shrunk onto this tube. The jacket covers the breech end of the gun and extends forward to the center of gravity. Built-up guns of larger caliber have one more layer of hoops in addition to the jacket, one layer of hoops usually extending to the muzzle.

The bore of the tube forms the powder chamber, the seat for the projectile and the rifled bore. Rifling consists of a number of helical grooves cut in the surface of the bore. The soft metal of the rotating band of the projectile is forced into these grooves causing the projectile to take up a rotary motion as it passes through the bore. This is necessary in order to keep the projectile stable in its flight.

TWIST.

The twist of rifling is usually expressed in the number of calibers length of bore in which it makes one complete turn. The twist actually required at the muzzle to maintain the stability of the projectile varies with the kind of projectile and the muzzle velocity. If a uniform twist be used, the driving force on the rotating band will be at a maximum when the pressure in the guns is at a maximum--or near the origin of rifling . The increasing twist serves to reduce the maximum driving force on the band thus lessening the danger of stripping the band. This is its principal advantage over the uniform twist, though it also reduces slightly the maximum pressure in the gun. The principal disadvantage of the increasing twist is the continued change in form of the grooves pressed in the rotating band, as the projectile passes through the bore. This results in increased friction and a higher value for the passive resistance than with a uniform twist. If the twist increases from zero at the breech uniformly to the muzzle, the rate of change in the tangent to the groove is constant. A twist in this form offers less resistance than the uniform twist to the initial rotation of the projectile. To still further diminish this resistance a twist that is at first less rapid than the uniformly increasing twist and later more rapid has been generally adopted for rifled guns.

Formerly in our service the twist was uniform; one turn in 25 calibres for guns and one turn in 20 calibres for howitzers. All the latest model army guns, however, have an increasing twist of one turn in 50 calibres at the breech to one turn in 25 calibres at a point from 2 to 4 calibres from the muzzle. In howitzers and mortars the twist is sometimes one turn in 40 calibres at the breech to one turn in 20 calibres at a point several calibres from the muzzle. Some mortars are rifled with a uniform twist and some guns have a rifling which begins with a zero twist.

OUTER CYLINDERS.

Outside of the tube is the jacket. It extends to the rear of the tube a sufficient distance to allow of seating the breech block. In this manner the longitudinal stress due to the pressure of the powder gases on the face of the breech block is transmitted to the jacket thus relieving the metal of the tube from this stress. In all built-up guns there is some method devised for locking the tube to the jacket so as to prevent relative movement of these parts.

Considering the gun alone the greatest range is obtained at an angle of about 43 degrees from that gun which fires the heaviest projectile with the greatest velocity. The caliber being limited to from 2.95 inch to 3.3 inch, the projectile is limited in weight to from 12 to 18 pounds. The weight of the gun is limited to between 700 and 1000 pounds and in length to between 27 and 36 calibers. The longer the gun, the greater the weight and velocity from the same charge of powder. A pressure of 33,000 pounds per square inch with a corresponding velocity of 1700 f. s. has been found to be as high a pressure and velocity as are desirable for a reasonable length of life for a field gun, the average life of which is 10,000 accurate rounds.

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