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Handbook of artillery : including mobile, anti-aircraft and trench matériel online

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Edward III, in 1340 by Lequesnoy before Mirepoix, in 1345 before
Monsegur, and in 1346 at Crecy; we have many instances of cannon
being used in the second half of the fourteenth century. About
1350 the North German knights had iron guns, and a little later the
Free Hanse Towns armed themselves in the same way. In the year
1356 appear large amounts in the accounts of the town of Nuremberg
as having been spent in purchasing cannon and guns; and in 1365
Duke Albert of Brandenberg defended Einbeck very effectually
"with fire boxes."

The first records show that the Huns used artillery at the siege of
Cividale, Italy, in 1331. The materiel was, of course, very crude and
its effectiveness at that time depended largely upon the smoke and
noise produced. The barrels, or cannons, in those days were con-
structed of wood, wrapped with wire or iron bands, and the pro-
jectiles were of stone. These guns were not mobile guns in any
sense; they were transported with the utmost difficulty, and were
subject to capture by sudden raids of the enemy.

The British were the first to actually bring the guns out into the
field of warfare. They appeared at the Battle of Crecy in 1346,
much to the dismay of the enemy. They shot anything that would
go into the barrels of the guns, even bundles of arrows. The ord-
nance department of Edward III consisted of 340 men, with but 12
artillerymen, showing that at that time not much attention was paid
to what is now an indispensable arm of the service. In 1415 the
numbers had increased to 25 " master-gunners " and 50 "servitour-
gunners." The gunner was the gun captain and had general charge
of the gun and stores. In action he laid the piece and did the actual
firing.

The early cannon of Europe were known by various names in the
different countries. In Italy they were known as bombardes,
probably derived from "a bombo et ardore" on account of the
great noise which the firing of them occasioned. The French called
them "quenon" or "cannon," the Germans "buchsen" or "boxes,"
and the Netherlanders "voghdeer" or " veugliares." Besides these
terms there were many others applied to the various models, but it
was not until the commencement of the fifteenth century that cannon
were classified and named according to their size. Cannon was not
adopted or manufactured in France until 1338, and even for many
years afterwards the French looked upon those nations who used
them as barbarians. The early cannon were made of wrought not
cast metal, the first account we have of cast cannon being in 1378,
when a founder named Aran, at Augsberg, in Germany, cast 30 of a
metal composed of copper and tin. In 1413 Mahomed II, at the
siege of Constantinople, had an enormous cast cannon. The bore



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is said to have boon 48 inches in diameter and the stone bullet to
have weighed 600 pounds.

The greatest example of artillery in the fifteenth century was at
the siege of Constantinople in 1453, by the Turks. They used a type
of mortar that hurled huge stones, some weighing 700 pounds.
Some of these guns survived to engage the British in 1807; the
majority of artillery at that date was for siege work. Barons who
had quarrels with their neighbors would rent ordnance and go out
and batter down their castles.

In the Italian wars waged by Charles VIII of France, artillery
played a conspicuous part. However, they lacked the necessary
mobility and, consequently, were captured and recaptured several
times in a single engagement. At that, artillery had done some
excellent work before small arms had attained any prominence.
Although field artillery was introduced in the Hussite Wars, 1419 to
1424, it was not until the Thirty- Years War that they really displayed
a mobile nature. The French had invented the limber, and the con-
nection between it and the gun trail was made with a rope. The
first gun that was moved by horsepower was mounted on an oblong
frame, the gunner sitting directly behind the piece. The forepart of
the oblong was mounted on two wheels and the rear end was supported
by the horse which was inside of the oblong frame. The majority
of the guns were 4-pounders, for as yet no way had been devised for
the proper transportation of the heavier guns.

About the middle of the eighteenth century, guns were either 24,
12, 6, or 3 pounders; the units were divided into brigades of 4, 5, and
6 guns respectively, and began to be separated into heavy and light
units. Each field gun was drawn by four horses with a cannoneer on
each of the lead horses. The ammunition carried was 100 rounds of
solid shot.

The howitzer, needed for its high angle of fire, put in its appearance
in 1785, being introduced by the French Army. Horse artillery
appeared in the French Army in 1791. In 1800 the horses were
paired off with a driver on each near horse as is done to-day. In 1808,
at Vimera, the first shrapnel came into use. It was known as case
shot and the type used by Napoleon had a fuze that could be used for
two different ranges. Napoleon also introduced the idea of massing
artillery along a long front. Between 1860 and 1870 rifling appeared;
this caused sighting to be given greater consideration, as a rifled gun
shoots very accurately. During our Civil War the smoothbore was
generally used, although rifled guns had made their appearance
toward the close of the conflict. Direct laying was the only method
of fire employed at this time. With the breechblock came the
quick-firing gun. This called for a recoil mechanism, in order that
the lay of the piece would not be seriously disturbed as a result of



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firing. The vast amount of smoke produced with the powder then
in use hid the target from the gunner and, unless quite a wind was
blowing, the shooting was slow, but with the development of smokeless
powder in the late nineties, this latter fault was done away with and
rapid firing was possible. The first shields were put on the guns
about this time also, protecting the gun personnel and making the
piece more difficult to put out of commission.

The recent great struggle in Europe has brought about conditions
and problems which heretofore have never existed in warfare. To
meet these, sweeping changes have been made in almost every arm
of the service, but probably the greatest and most radical change
has been the motorization of the artillery.

Heretofore successful advances by the troops were limited to
comparatively short distances, due to the impossibility of advancing
artillery, ammunition, and supplies over grounds which are often
muddy, full of shell holes, and otherwise difficult to maneuver with
enough rapidity to keep up with the advancing infantry troops.
The problem of transporting army equipment in the field led to the
introduction of tractors and motor trucks.

The development of the caterpillar tractor used for hauling field
artillery, which is able to negotiate almost any kind of terrain on the
battle field, led to the question of the possibility of mounting guns
directly on a self-propelled vehicle equipped with caterpillar treads.
Early in 1918, an 8-inch howitzer was mounted on a self-propelled
caterpillar and was fired at angles of elevation varying from to 45
with very satisfactory results. This experimental caterpillar was
tested, and it was found to be practical, easy to maneuver, and able
to withstand the firing strain of the howitzer. As a result of this
test, several types of experimental self-propelled caterpillar units
are being built with armaments varying from 75-millimeter guns to
240-millimeter howitzers.



ARTILLERY.



Artillery has come to mean all firearms not carried or used by hand,
excepting machine guns. Artillery is divided into two general classic
fications: Artillery of position and mobile artillery.

Artillery of position is that which is permanently mounted in forti-
fications.

Mobile artillery consists of two classes: First, the artillery designed
to accompany an army in the field; second, railway artillery, which
requires tracks for its transportation. The first type only is dis-
cussed in this book.

MOBILE ARTILLERY.

In designing any gun intended for use in the field, there are two
important requirements power and mobility. Granting that a
general type of gun has been decided upon, it is evident that any
increase in either of these two factors is at the expense of the other.
It is necessary to balance the two, keeping in mind the specific purpose
of the gun under consideration. We thus find it necessary to have
several distinct classes of guns, ranging from the very powerful and
almost immobile, to the very mobile and comparatively weak. The
general classification is heavy field, light field, mountain guns or
pack howitzers, trench mortars, and infantry accompanying guns and
howitzers.

Besides this classification, based upon power, there is a second,
based upon the shape of the trajectory. For the attack of targets
that can be reached by it, flat trajectory fire is prefesred on account
of its power and accuracy. Cases frequently arise, however, where
such fire is useless, either the gun or its target being so concealed and
sheltered by intrenchments or the condition of the terrain that higher
angles of departure and fall become necessary.

To provide for both cases, there are two or three types of
weapon the long gun for flat trajectory, the shorter howitzer for
curved trajectory, and sometimes the still shorter mortar for high-
angle fire. We thus subdivide our original classes and distinguish,
for example, the light field howitzer, the heavy field gun, etc. Evi-
dently the number of separate calibers that might be adopted to
make up a complete series of types is very large. But it is impor-
tant to reduce this number to a minimum, both from considerations
of economy and also to avoid complication in ammunition supplies.

Guns were ordinarily intended for attack of targets that can be
reached by direct fire; that is, by fire at angles of elevation not exceed-

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ing about 15. For the attack of targets that are protected against
direct fire and for use in positions that are so sheltered that direct
fire can not be utilized, curved fire that is, fire at elevations exceed-
ing 15 is necessary. There is, therefore, provided the howitzer, a
short gun designed to fire at comparatively large angles of elevation.

Field guns are now designed which permit fire at elevations as
high or higher than is permitted by the howitzers. This is partic-
ularly true of anti-aircraft guns and those designed for use against
entrenched positions. This development is an improvement in the
effectiveness of the field gun, -but it will not eliminate the use of
howitzers of equal mobility, as the latter use projectiles of much
greater weight than that of same caliber gun materiel.

The original American plan of field artillery design provided for
each caliber of gun a howitzer of equal degree of mobility. In fur-
therance of this idea and to reduce to a minimum the number of
calibers of mobile artillery and thus simplify as far as possible the
supply of ammunition, the calibers of the guns and howitzers were
so selected that while both guns and howitzers fulfilled the require-
ments as to weight and power for each degree of mobility the caliber
of each was the same as that of the gun of the next lower degree of
mobility. That is, the howitzer corresponding in mobility to one of
the guns is of the same caliber as the next heaviest gun. The recent
developments in American artillery, as well as the introduction of
artillery of foreign design into the American service, have sustained
this principle.

Under ordinary conditions the 3-inch field gun with its weight of
about 3,900 pounds behind a six-horse team, is about as powerful a
gun as can follow an army in motion. For this reason a gun of ap-
proximately this caliber has been adopted by most nations as the
principal field gun.

The artillery of all military powers now comprises what are known
as " rapid-fire " or " quick-firing " guns. This designation is too firmly
established to be changed, although it can not be considered as accu-
rately descriptive since rapidity of fire is characteristic of nearly all
modern types. The real distinguishing mark of a rapid-fire gun is that
its carriage does not move materially in firing; instead, the gun recoils
on the carriage and is returned to the firing position by springs or
their equivalent. There are a number of other features, some of
which are found in all rapid-fire models; but these are of secondary
significance and either old ideas which could not be worked out
practically before the development of the gun-recoil carriage or else
improvements developed since in the effort to get the best results out
of it. For example, it is useless to attach shields to a rigid carriage,
for, since the cannoneers have to stand clear to avoid the recoil, they
can not take advantage of them. Mechanism for traversing the



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piece on its carriage is unnecessary with the rigid system, but be-
comes necessary as soon as we adopt a carriage that remains more or
less firmly anchored to the ground. Fixed ammunition and instru-
ments for indirect laying are not essentially a part of either a rigid or
a gun-recoil system; they are sometimes used with the former and
occasionally, but rarely, omitted from the latter; but they have their
full value only in rapid-fire material.

Our mobile artillery is divided into the following classes:

(a) Divisional artillery, such as the 3-inch, 75 millimeter guns, and
155 millimeter howitzers.

(6) Corps artillery, such as the 4.7-inch and 155 millimeter guns.

(c) Army artillery, such as the 8-inch and 240 millimeter. Any
caliber may, if required, be assigned to army artillery corps.
U (d) Mountain or pack materiel transported on the backs of mules.
For mountain service the system composed of gun and carriage must
be capable of rapid dismantling into parts, none of which forms too
heavy a load for a pack mule. The weight of the load including the
saddle and equipment should not exceed 350 pounds. The mountain
gun in our service is the 2.95-inch.

(e) Infantry accompanying guns, such as 37 millimeter.

(f) Trench mortars.



GUNS.



THEIR FUNCTIONS AND CONSTRUCTION.

U A gun is a machine by which the force of expanding gas is used
for the purpose of propelling a projectile in a definite direction."

The gun consists of a metal tube, closed at one end, of sufficient
strength to resist the pressure of the expanding gases, in which is
placed a projectile designed to move through the tube. The force
of the expanding gases acting on the base of the projectile causes
it to start on its flight in a definite direction. When the charge is
ignited, the explosion or rapid combustion of the powder gives rise
by its decomposition to a large amount of gas, which tends to expand,
and to occupy a space greater than that in which the powder was
originally contained; consequently, it exerts a pressure in all direc-
tions, and the energy developed is utilized in forcing the projectile
from the tube. The major portion of the energy is distributed as
follows :

(a) Energy of translation of the projectile.

(&) Energy of rotation of the projectile.

(c) Energy of translation, in recoil, of the gun.

(d) Energy of translation of the unburnt charge and gases.

(e) Energy consumed in overcoming the passive resistance of the
projectile. This resistance arises from the friction of the projectile
against the walls of the bore, and of the rotating band against the
driving edges of the lands. In the first stages it also arises from the
cutting of grooves in the rotating band by the lands.

The balance of the energy is expended by being lost as heat to the
gun and that which remains in the gas as sensible or latent heat

It may be readily understood that during the travel of the pro-
jectile through the bore of the gun, from the instant of ignition of the
charge until it has left the muzzle, tremendous rending stresses are
set up in the tube. In the earlier days of ordnance construction,
these stresses were met by sheer weight of metal; but as the weight
of projectiles increased, with consequent increase in powder charges,
this weight of metal became so great as to impede the desired mobility
of the material. Consequently, forgings of refined and alloyed steels
took the place of the castings or forgings of iron or simple steels.

As explosives increased in power, the plain tube, even though built
of alloyed steels, became incapable of containing the chamber pres-
sures, even though of excessive weight. This problem was finally
met through the construction of built-up and wire-wrapped guns.

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25

A gun is subjected to two fundamental stresses a circumferential
tension tending to split the gun open longitudinally, and a longitudi-
nal tension tending to pull the gun apart lengthwise. The longitudinal
strength of a gun is usually greatly in excess of any requirements.
It is easy to demonstrate that any homogeneous gun, i. e., a gun made
of solid material and not built up, soon reaches the limit of thickness
beyond which additional thickness is practically useless in giving
strength to resist circumferential stress. This is due to the fact that
the stress on the metal near the bore is far higher than that on the
outer portion and soon reaches its maximum resistance, which addi-
tional thickness of metal does not materially increase. The gun can,
however, be arranged to withstand a considerably higher piessure
by building it up on the principle of initial tensions. The inner lay-
ers of the metal are thereby compressed so that the gas pressure has
first to reverse this compression and then extend the metal. The
gun barrel (or tube) supported by the contraction of the outer hoops
will then be able to endure a gas pressure which can be expressed as
proportional to the initial compression plus the extension, whereas in
the old type of solid gun it was proportional to the extension only.

In the built-up system, the outer jackets are shrunk one over the
other so that the inner tube is placed in compression and the outer
ones in tension.

In place of one or more of the jackets, a thin wire or ribbon of steel
is sometimes wound around the tube and has exactly the same effect
as shrinking thin jackets one over the other. This type is known as
the wire-wound gun.

Guns may be composed of two, three, or more cylinders; though in
practice guns are hardly ever built of more than four cylinders. All
Army guns, except small howitzers or mortars, are of the built-up or
wire-wrapped type.

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 and causes the projectile to take up the
motion of rotation as it passes through the bore.

Rotation of the projectile around its longer axis is necessary for
stability in flight. By twist of rifling is meant the inclination of one
of the grooves to the element of the bore at any point. Rifling is of
two kinds:

(a) Uniform twist, or that in which the twist is constant through-
out the bore.

(6) Increasing twist, or that in which the twist increases from the
breech toward the muzzle end of the bore.

The twist of rifling is usually expressed in number of calibers length
of bore in which it makes one complete turn; this is called the twist
in calibers. The twist actually required at the muzzle to maintain



26

the stability of the projectile in flight varies with the kind of pro-
jectile and with the muzzle velocity.

If a uniform twist is used, the driving force on the rotating band
will be a maximum when the pressure in the gun is at 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 it with resultant loss of rotation of the projectile. This is
its principal advantage over the uniform twist, though it also reduces
slightly the maximum pressure in the gun. The principal disad-
vantage of increasing t wist is the continued change of form neces-
sary in 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 muz-
zle, the rate of change in the tangent to the groove is constant. A
twist in this form would offer less resistance than the uniform twist
to the initial rotation of the projectile. But 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 adopted for some
rifled guns.

The breech mechanism comprises the breech block, the firing mechan-
ism, and the mechanism for the insertion and withdrawal of the block.
There are two general methods of closing the breech. In the first
method the block is inserted from the rear. The block is provided
with screw threads on its outer surface which engage in correspond-
ing threads in the breech of the gun. In order to facilitate insertion
and withdrawal of the block, the threads on the block and breech
are interrupted. The surface of the block is divided into an even
number of sectors and the threads of the alternate sectors are cut
a vay. Similarly, the threads in the breech are cut away from those
sectors opposite the threaded sectors on the block. The block may
then be rapidly inserted nearly to its seat in the gun, and when turned
through a comparatively small arc, say one-eighth or one-twelfth of
a circle, depending upan the number of sectors into which the block
is divided, the threads on the block and in the breech are fully
engaged and the block is locked.

In the second method, a wedge-shaped block is seated in a slot cut
in the breech of the gun at right angles to the bore and slides in the
slot to close or open the breech.

Variations of these two methods will be noted in the detailed
descriptions of the guns which follow:

The most notable variation from the above two types is the Nor-
denfeld type of breech mechanism, a rotating block construction
found on the French 37-millimeter and 75-millimeter, described
more fully and illustrated in the description of these guns.



27

The breechblock is usually supported in the jacket of the gun or
in a breech ring screwed into the jacket. The seat in the jacket
being of greater diameter than could be provided in the tube, the
bearing surface of the screw threads on the block is increased and
and the length of the block may be diminished.

The slotted screw breechblock is used to a great extent in oui
service. Its advantages are uniform distribution in the gun of the
longitudinal stress produced by the powder pressure and lightness
permitted in the construction of the breech end of the gun. In the
model of 1917, 3-inch anti-aircraft gun, however, and in the Ameri-
can 75-millimeter gun, the sliding block operating vertically has been
adopted for the reason that it permits of simpler mechanism for
semiautomatic operations.

Howitzers differ only slightly from guns in their construction.
They are shorter in length and insomuch as the chamber pressures
differ materially the necessity for the long jacket is eliminated.
A shorter jacket, extending only a part of the length of the tube,
shrunk on in the same manner, is generally used.

Interior/ ballistics treats of the motion of the projectile while still
in the bore of the gun. It includes the study of the mode of combus-
tion of the powder, the pressure developed, and the velocity of the
projectile along the bore of the gun.

By means of the formulas developed, a study of interior ballistics
has made it possible to design the granulation of the powder for a
given gun so as to obtain the highest possible muzzle velocity with
a given weight of projectile, while keeping the pressure along the
bore within the limits imposed by the strength of the walls of the
gun, and the weight of the charge low enough for convenient loading.

After the calculation of curves of velocity and pressure are made,
the walls of the gun are calculated to withstand the expected pres-
sure at each point from breech to muzzle.



MOUNTS FOR MOBILE ARTILLERY.



A modern gun carriage is expected to stand steady on firing, so that
in the first place it requires no running up, and in the second place
it maintains the direction of the gun so that only a slight correction
in elevation and direction is required after each round. The car-


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Online LibraryUnited States. Army. Ordnance DeptHandbook of artillery : including mobile, anti-aircraft and trench matériel → online text (page 2 of 19)