On the introduction of iron ships it was found that the ordinary cast-iron
projectile readily pierced the thin plating, and in order to
protect the vital parts of the vessel wrought-iron armour of
considerable thickness was placed on the sides. It then became
necessary to produce a projectile which would pierce this
armour. This was effected by Sir W. Palliser, who invented
a method of hardening the head of the pointed cast-iron
shot. By casting the projectile point downwards and forming
the head in an iron mould, the hot metal was suddenly
chilled and became intensely hard, while the remainder
of the mould being formed of sand allowed the metal to
cool slowly and the body of the shot to be made tough.
These shot proved very effective against wrought-iron armour,
but were not serviceable against compound and steel armour.
A new departure had, therefore, to be made, and forged steel
shot with points hardened by water, &c., took the place of
the Palliser shot. At first these forged steel shot were made
of ordinary carbon steel, but as armour improved in quality
the projectiles followed suit, and, for the attack of the
latest type of cemented steel armour, the projectile is formed
of steel -- either forged or cast -- containing both nickel and
chromium. Tungsten steel has also been used with success.
Armour-piercing shot or shell are generally cast from a
special mixture of chrome steel melted in pots; they are
afterwards forged into shape. The shell is then thoroughly
annealed, the core bored and the exterior turned up in the
lathe. The shell is finished in a similar manner to others
described below. The final or tempering treatment is very
important, but details are kept strictly secret. It consists
in hardening the head of the projectile and tempering it in
a special manner, the rear portion being reduced in hardness
so as to render it tough. The cavity of these projectiles
is capable of receiving a small bursting charge of about
2% of the weight of the complete projectile, and when
this is used the projectile is called an armour-piercing
shell. The shell, whether fuzed or unfuzed, will burst
on striking a medium thickness of armour. Armour-piercing
shells, having a bursting charge of about 3% of the weight
of the complete projectile, are now often fitted with a soft
steel cap for the perforation of hard steel armour.
For the theory of the action of the cap see ARMOUR PLATES.
Even with these improvements the projectile cannot,
with a reasonable velocity, be relied upon to pierce one
calibre in thickness of modern cemented steel armour.
Explosive shells do not appear to have been in general
use before the middle of the 16th century. About that
time hollow balls of stone or cast iron were fired from
mortars. The balls were nearly filled with gunpowder and the
remaining space with a slow-burning composition. This plan
was unsatisfactory, as the composition was not always ignited
by the flash from the discharge of the gun, and moreover the
amount of composition to burn a stipulated time could not
easily be gauged. The shell was, therefore, fitted with a
hollow forged iron or copper plug, filled with slow-burning
powder. It was impossible to ignite with certainty this
primitive fuze simply by firing the gun; the fuze was
consequently first ignited and the gun fired immediately
afterwards. This entailed the use of a mortar or a very short
piece, so that the fuze could be easily reached from the muzzle
without unduly endangering the gunner. Cast-iron spherical
common shell were in use up to 1871. For guns they were
latterly fitted with a wooden disc called a sabot, attached
by a copper rivet, intended to keep the fuze central when
loading. They were also supposed to reduce the rebounding
tendency of the shell as it travelled along the bore on
discharge. Mortar shell were not fitted with sabots.
Cast iron held its own as the most convenient material
for projectiles up to recent years, steel supplanting it,
first for projectiles intended for piercing armour, and
afterwards for common shell for high-velocity guns where the
shock of discharge has been found too severe for cast iron.
Common shell is essentially a material destructor. Filled
with ordinary gunpowder, the larger natures are formidable
projectiles for the attack of fortifications and the
unarmoured portions of warships. On bursting they break up
into somewhat large pieces, which carry destruction forward
to some distance from the point of burst. For the attack of
buildings common shell are superior to shrapnel and they are
used to attack troops posted behind cover where it is impossible
for shrapnel to reach them; their effect against troops is,
however, generally insignificant. When filled with lyddite[?],
melinite[?], &c., they are called high-explosive (H.E.) shell (see below). Common shell for modern high-velocity guns may be made of cast steel or forged steel; those made of cast
iron are now generally made for practice, as they are found
to break up on impact, even against earthworks, before the
fuze has time to act; the bursting charge is, therefore, not
ignited or only ignited after the shell has broken up, the
effect of the bursting charge being lost in either case. So
long as the shell is strong enough to resist the shocks of
discharge and impact against earth or thin steel plates, it
should be designed to contain as large a bursting charge as
possible and to break up into a large number of medium-sized
pieces. Their effect between decks is generally more
far-reaching than lyddite shell, but the purely local effect is
less. Light structures, which, at a short distance from the
point of burst, successfully resist lyddite shell and confine
the effect of the explosion, may be destroyed by the shower
of heavy pieces produced by the burst of a large common shell.
To prevent the premature explosion of the shell, by the
friction of the grains of powder on discharge, it is heated
and coated internally with a thick lacquer, which on cooling
presents a smooth surface. Besides this the bursting charge
of all shell of 4-inch calibre and upwards (also with all other
natures except shrapnel) is contained in a flannel or canvas
bag. The bag is inserted through the fuze hole and the
bursting charge of pebble and fine grain powder gradually poured
in. The shell is tapped on the outside by a wood mallet to
settle the powder down. When all the powder has been got
in, the neck of the bag is tied and pushed through the fuze
hole. A few small shalloon primer bags, filled with seven
drams of fine grain powder, are then inserted to fill up the
shell and carry the flash from the fuze through the burster bag.
In the United States specially long common shell called torpedo
shell, about 4.7 calibres in length, are employed with the
coast artillery 12-inch mortars. They were made of cast steel,
but owing to a premature explosion in a mortar, supposed to
be due to weakness of the shell, they are now made of forged
steel. The weight of the usual projectile for this mortar is 850
pounds. The torpedo shell, however, weighs 1000 pounds and contains
137 pounds of high explosive; it is not intended for piercing
armour but for producing a powerful explosion on the armoured
deck of a warship. The compression, and consequent generation
of heat on discharge of the charge in these long shell,
render them liable to premature explosion if fired with high
velocities. Some inventors have, therefore, sought to overcome
this by dividing the shell transversely into compartments
and so making each portion of the charge comparatively short.
Cast-steel common shell are cast in sand moulds head
downwards from steel of the required composition to give the
proper tenacity. A large head, which is subsequently removed,
is cast on the base to give solidity and soundness to the
castings. The castings are annealed by placing them in a
furnace or oven until red hot, then allowing them to cool
gradually. The process of casting is very similar to
that for the old cast-iron common shell, which, however,
were cast base downwards. The steel castings after being
annealed are dressed and carefully examined for defects.
The exterior of the body is generally ground by an emery
wheel or turned in a lathe; the groove for the driving band
is also turned and the fuze hole fitted with a gun-metal
bush. Forged-steel common shell are made from solid steel
billets. These are heated to redness and shaped by a series
of punches which force the heated metal through steel dies
by hydraulic pressure. If the shell is intended for a
nose fuze the base end is shaped by the press and the head
subsequently formed by a properly shaped die, or, in the case
of small shell, the head can, when red hot, be spun up in a
lathe by a properly formed tool. For a base fuze shell the
head is produced by the punches and dies, and the base is
subsequently formed by pressing in the metal to the desired
shape. The shell is then completed as described above.
High-explosive shell, as used in the English service,
are simply forged-steel common shell filled with lyddite and
having a special nose fuze and exploder. The base end of
lyddite shell is made solid to prevent the possibility of the
gas pressure in the gun producing a premature explosion. In
filling the shell great precautions are necessary to prevent
the melted lyddite (picric acid) from coming in contact with
certain materials such as combinations of lead, soda, &c.,
which produce sensitive picrates. The shell are consequently
painted externally with a special non-lead paint and lacquered
inside with special lacquer. The picric acid is melted in an
oven, the temperature being carefully limited. The melted
material is poured into the shell by means of a bronze
funnel, which also forms the space for the exploder of picric
powder. On cooling, the material solidifies into a dense, hard
mass (density 1.6), in which state it is called lyddite.
The fuze on striking ignites the exploder and in turn the
lyddite. When properly detonated a dense black smoke is
produced and the projectile is broken up into small pieces,
some of which are almost of the fineness of grains of sand.
The radius of the explosion is about 25 yards, but the local
effect is intense, and hence on light structures in a confined
space the destruction is complete. The shell is only of use
against thin plates; against modern armour it is ineffective.
When detonation has not been complete, as sometimes happens
with small shells, the smoke is yellowish and the pieces of the
exploded shell are as large as when a powder burster is used.
The French high-explosive shell obus torpille or obus
a melinite was adopted in 1886. The melinite was
originally filled into the ordinary cast-iron common shell
(obus ordinaire) with thick walls, but soon afterwards a
forged-steel thin-walled shell (obus allonge) was introduced.
To explode the shell a steel receptacle (called a gaine) is
screwed into the nose of the shell. It is filled with explosive
and fitted with a detonator which is exploded by a percussion
fuze. Except for the means adopted to ensure detonation
this shell is practically the same as the lyddite shell.
Picric acid in some form or other is used in nearly all
countries for filling high-explosive shell. In some the
explosive is melted and poured into cardboard cases instead
of being poured directly into the shell. The cases are placed
in the shell either by the head of the shell unscrewing from
the body or by a removable base plug. The French melinite
and the Italian pertite are believed to be forms of picric
acid. Russia and the United States use compressed wet gun-cotton
(density 1.2) as the charge for their high-explosive shell.
The gun-cotton is packed in a thin zinc or copper case and is
placed in the shell either by the head or base of the shell being
removable. The gun-cotton is detonated by a powerful exploder,
the form of which differs in each country. Ammonal is also
used in high-explosive shell, but owing to its light density
it is not in great favour. For field-gun and other small
high-explosive shells, ordinary smokeless powder is often used.
Double shell is a term given to a common shell which was
made abnormally long, so as to receive a large bursting
charge. They were intended to be fired with a reduced charge
at short range. They are now practically obsolete; their
place with modern B.L. guns has been taken by high-explosive
shell. Star shell are intended for illuminating the enemy's
position. They are very similar to shrapnel shell,
composition stars made up in cylindrical paper cases taking
the place of the bullets. The shell on bursting, blows
off the head and scatters the ignited stars. This shell
is only supplied to mountain guns and howitzers, and takes
the place of the older types of illuminating shell, viz.
the ground light ball and the parachute light ball.
Hand grenades were used at the assault of entrenchments or in boat attacks. Although generally regarded as obsolete, they were much used by the Japanese at the siege of Port Arthur (Lushun)[?], 1904. In the British service they were small, thin, spherical common shell weighing three pounds for land service and six pounds for sea service, filled with powder. They were fitted with a small wood time fuze to burn 7.5 seconds. The grenade was held in the hand and the fuze lighted by a port-fire. It was then thrown some 20 to 30 yards at the enemy's works or boats. Sometimes a number were fired from a mortar at an elevation of about 30 degrees so that none should strike the ground too near the mortar.
New types of grenades filled with high explosives detonated by
a percussion fuze have been produced of late years, and it is
probable that they will be again introduced into most countries.
Shrapnel shell were invented by Lieutenant (afterwards
Lieutenant-General) Henry Shrapnel, R.A. (1761-1842), in
1784. They were spherical common shell with lead bullets
mixed with the bursting charge. Although far superior to
common shell in man-killing effect, their action was not
altogether satisfactory, as the shell on bursting projected
the bullets in all directions, and there was a liability
of premature explosion. In order to overcome these
defects Colonel Boxer, R.A., separated the bullets from the
bursting charge by a sheet-iron diaphragm -- hence the name
of "diaphragm shell." The bullets were hardened by
the addition of antimony, and, as the bursting charge was
small, the shell was weakened by four grooves made inside
the shell extending from the fuze hole to the opposite side.
With rifled guns the form of the shell altered, but its character
remained. The body of the shell was still made of cast iron
with a cavity at the base for the bursting charge; on this
was placed a thick steel diaphragm with a hollow brass tube
which communicated the flash from the nose fuze to the bursting
charge. The body was filled with hard lead bullets, and
a wood head covered with sheet iron or steel surmounted it
and carried the fuze. By making the body of toughened steel
and by slightly reducing the diameter of the bullets,
the number of bullets contained was much increased. In the
older field shrapnel, bullets of 18 and 34 to the pound were
used; for later patterns see table in ORDNANCE: Field
Equipments. Thus with the cast-iron body the percentage
of useful weight, i.e. the proportion of the weight of
the bullets to the total weight of the shell, was from 26 to
28%, while with modern steel shell it is from 47 to 53%. The
limit of the forward effect of shrapnel at effective range
is about 300 yards and the extent of front covered 25 yards.
Shrapnel and high-explosive shells, burst in the air with a time
fuze in the usual way, have differing effects. It will be seen that the shrapnel bullets sweep an area of about 250 yards by 30 yards, half
the bullets falling on the first 50 yards of the beaten
zone. With the high-explosive shell, however, the fragments
strike the ground closer to the point of burst and beat a
shallow, but broad, area of ground (about 7 yards by 55
yards). These areas show the calculated performance of
the German field gun (96 N.A.), firing at a range of 3300
yards. In the case of the high-explosive shell, the
concussion of the burst is highly dangerous, quite apart
from the actual distribution of the fragments of the shell.]
The term "shooting shrapnel" is given to certain
howitzer shrapnel, which are designed to contain a large
bursting charge for the purpose of considerably augmenting
the velocity of the bullets when the shell bursts.
High-explosive shell of a compound type have also lately
appeared. Messrs Krupp have made a kind of ring shell with
a steel body; a central tube conveys the flash from the
fuze to a base magazine containing a smoke-producing charge,
while surrounding the central tube is a bursting charge of
ordinary smokeless nitro-powder. A shrapnel on somewhat
similar lines has been made by Ehrhardt; in form it
is an ordinary shrapnel with base burster, but near the head
is a second magazine filled with a high-explosive charge;
this is attached to the end of the fuze and is so arranged
that when the shell is burst as time shrapnel the flash
from the fuze passes clear of the high-explosive magazine
and ignites only the base magazine, the bullets being blown
out in the usual manner. When, however, the fuze acts on
graze, the percussion part detonates the high-explosive
charge and the bullets are blown out sideways and thus reach
men behind shields, &c. There is some loss of
bullet capacity in this shell, and it appears likely that the
bullets will be materially deformed when detonation occurs;
the advantages may, however, counterbalance their objections.
Segment and ring shell are varieties of shrapnel, the
interior of the shell being built up of cast-iron segments
or rings (which break up into segments) about a tinned-iron
cylinder which formed the magazine of the shell. The shell
was completed by a cast-iron body formed around the segments or
rings. The German army in 1870 employed ring shell almost
exclusively against the French. The French found that common
shell (obus ordinaire) when made of cast iron broke up on
bursting into a small number of irregularly shaped pieces, and
in order to obtain a systematic fragmentation for small shells
they adopted a variety of projectiles of the segment and shrapnel
types. With the improvements made latterly these have become
obsolete, and the French system does not now materially differ
from that employed in England and other countries. The old
shell are, however, of sufficient interest to be enumerated;
thus the "double-walled shell" (obus a double parol) was
built up of two shells, the internal portion had a cylindrical
chamber for the bursting charge, but on the outside it was so
shaped as to break up into well-defined pieces; the external
portion of the shell was cast around the internal part, and
also broke up into a number Of pieces; this shell was liable
to premature explosion. The obus a couronnes de balles
(1879) was practically a segment shell with cast-iron balls
in lieu of segments; thin iron partitions separated each
layer, and the balls were flattened where they came in contact
with the plates. The obus a balles libres, adopted in
1880, were of the same type, but there were no separating
plates. The obus a anneaux was simply a ring shell of
the same type as used in England. The obus a mitraille
adopted in 1883 for field and siege guns had a cast-iron
disc for its base with the body built up of segments and
steel balls; a hollow ogival head surmounted this and a thin
steel envelope bound all together. The head was filled with
powder and fitted with a fuze; on explosion the head burst
and rupturing the envelope set free the balls and segments.
It is of importance in firing shrapnel shell that the position
of the burst shall be plainly seen. With the larger patterns
of shell this presents no difficulty, but with the shrapnel
for field guns which contain a small bursting charge only,
and at long range in certain states of the atmosphere, the
difficulty becomes pronounced. The problem has been solved in
some cases by packing the bullets in fine grain black powder
(instead of resin) and compressing both bullets and powder in
order to prevent the generation of heat when the bullets set
back on the discharge of the gun. In Germany a mixture of
red amorphous phosphorus and fine grain powder is used for the
same purpose and produces a dense white cloud of smoke. In
Russia a mixture of magnesium and antimony sulphide is used.
