EXPLOSIVES, AMMUNITION AND FUSES.
EXPLOSIVES.
As a matter of practical interest, explosives may be divided into three
classes, namely:
(1) Progressive or =propelling explosives= called =low explosives=.
(2) Detonating or =disruptive explosives=, termed =high explosives=.
(3) =Detonators= or exploders, known as =fulminates=.
The first includes all classes of gun powders used in firearms of
all kinds; the second, explosives used in shell, torpedoes, and for
demolitions; the third, those explosives used to originate explosive
reactions in the two first classes. Corresponding names are given
to the phenomena characteristic of each class of explosives, (1)
explosions proper, of low order, progressive, or combustions, (2)
detonations, of high order, (3) fulminations, this last possessing
exceptional brusqueness.
The explosion of low order is marked by more or less progression; the
time element is involved as a controlling factor, the time required to
complete the explosive reaction being large compared with that of the
other forms of explosion.
The second class of explosion is of a different nature. The explosive
reaction is not limited or confined to the surfaces exposed but appears
to progress in all directions throughout the mass radially from the
point of initial explosion. It has been determined experimentally that
the velocity of propagation of the explosive wave throughout a mass of
guncotton is from 17,000 to 21,000 feet per second.
Fulmination is a class of explosion still more brusque than the
last. The abruptness of their explosion and the consequent sharpness
of the blow and the concentration of heat on the point of ignition
constituting their efficiency as originators of explosions of the first
two classes.
=Methods of Exploding.= Explosives may be exploded by three methods; in
reality but two, by heat and by application of energy as by a blow. The
heat may be applied directly by friction, by electricity and detonating
cap, these two methods of applying the heat giving rise to the three
practical methods above mentioned. As it is not practical to apply heat
directly to the charge, small charges of special explosives are made up
into primers and these are exploded in one of the ways above mentioned
and so communicate the explosion to the main charge. Fulminate of
mercury is one of the high explosives fulfilling the requirements and
it is readily exploded by any one of the methods mentioned. It is used
in all detonating caps. Primers for cannon also contain an additional
charge of black powder to increase the flame. For this purpose also
igniting charges of black powder are attached to the smokeless powder
charges for the larger calibers.
=Uses.= The chief use of low or progressive explosives is as a
propelling charge in guns and for blasting where it is desired to exert
a pushing effect rather than a blow. High explosives are used when it
is desired to exert a high pressure and shatter the container, as in
a shell, mine, etc. This class is not satisfactory as a propelling
charge for the reason that its rapidity of action is so great that
the pressure exerted would burst the gun before the projectile could
start. Low explosives are not satisfactory shell fillers for the reason
that their action is so low that the shell would break at its weakest
point before all the explosives had exploded and what remained would
be wasted. With a high explosive, all or most of the charge explodes
before the shell can break up. The greater the rapidity of action of an
explosive the finer the fragmentation of the projectile. With too rapid
action the pieces are too small; with too slow action they are too
large. Experience teaches the proper rapidity of action to attain the
fragmentation most efficient against animate and material targets.
=Propelling Charges.= Up to the present time nitrocellulose powder has
complied better with the requirements of a suitable, smokeless powder
than any other that has been proposed and is used in our service for
propelling charges in guns. The danger of manufacture is also less than
that of nitroglycerine powders. Moreover the latter, which was formerly
used in our service and still is in the British and some others, causes
too much erosion of the tubes due to the greater heat of explosion. It
has the advantage of requiring a smaller charge for the same muzzle
velocity and therefore a smaller powder space and consequent lighter
weight of gun.
=Shell Fillers.= High explosives for shell fillers. Up to the present
explosive “D,” trinitrotoluol and picric acid are the principal high
explosives which fulfill the requirements as shell fillers. Explosive
“D” on account of its great insensitiveness to shock is used in armor
piercing projectiles and also in field gun and howitzer shell. It is
detonated by a fuze. Trinitrotoluol is used in submarine mines and in
general demolition work as it is much easier to explode than explosive
“D.”
=Table of Explosives.= The following table gives a good idea of the
principal explosives in use in our service and the characteristics of
each:
High
Purpose. or Low. Name.
Propelling charge in guns. L Nitrocellulose, smokeless
powder.
Bursting charge, projectiles. H Picric acid, explosive “D”
(powder form)
Trinitrotoluol.
Blank, saluting charges. L Black Powder.
Re-inforce charges, primers. L Black Powder.
Base charge, shrapnel. L Black Powder.
Time trains, fuzes. L Black Powder.
Igniting charges, cannon. L Black Powder.
Charges, submarine mines. H Trinitrotoluol wet guncotton.
Igniting elements, fuzes H Fulminate of mercury, chlorate
and primers. of potash (potassium
chlorate).
=High Explosives.= The principal high explosives used as shell fillers
in our service are: picric acid, explosive “D” and trinitrotoluol,
or more popularly known at TNT. The picric acid and picrates used as
shell fillers are secret compositions. Mellinite, essentially picric
acid alone or with some other substance is used as a shell filler by
the French. It is poured into the shell in a fused state and allowed
to harden, thus giving a very compact charge and one easily handled.
It has the disadvantage however of forming unstable compounds with
the metal of the shell and great care must be exercised in coating
the interior of the shell with a protective coat before pouring in
the fused mellinite. Lyddite is the English equivalent of mellinite.
Picric acid was also used by the Japanese or it may be a mixture of
picric acid and some nitro compound. The most successful explosive of
this type is explosive “D” invented by Colonel Dunn of our Ordnance
Department and sometimes known as “Dunnite.” It is not fusible and
must be compressed for use as a shell filler, being forced into the
shell by compression. This is a disadvantage as compared to mellinite
as the density of loading is less and weight for weight therefore less
efficient. It is little sensitive to shock and therefore not very
dangerous to load even under great pressure. Trinitrotoluol is also
used as a shell filler but its chief use is in demolition work and as
the charge for submarine mines.
=Nitrogen Compounds.= It may be interesting to note that all of the
principal explosives with which we have been dealing are compounds
containing nitrogen. In fact the war has been fought with fixed
nitrogen which explains the great interest taken in the various
attempts to fix the free nitrogen of the air which is the world’s great
storehouse of free nitrogen. As nitrogen is also a necessary ingredient
in the various fertilizers, the result to the world of a commercial
process for speeding up the cycle of changes through which nitrogen
passes in its life giving mission from free nitrogen in the air to its
various compounds in the nitrogeneous animal and vegetable tissues is
almost limitless and as usual war has been the incentive to speed up a
process which will result in incalculable value to mankind.
=Classification.= Guns are loaded with three kinds of ammunition:
fixed, semi-fixed and separate loading ammunition. In fixed ammunition
the round is complete and projectile and powder loaded into the chamber
at the same time. In semi-fixed the projectile is separate from the
powder charge, which however is put up and loaded into the chamber in a
container. In separate loading ammunition the powder is loaded into the
chamber in bags. In the first two cases the cartridge case furnishes
the means for sealing the rear of the powder chamber against escape to
the rear of the powder gases. In the last case some form of obturating
device is made a part of the breechblock furnishing a gas check to seal
the rear of the powder chamber.
=Fixed Ammunition.= All of our field guns below 5 inches in calibre use
fixed ammunition. The powder is placed loose in the cartridge case,
the space not filled with powder being stuffed with packing paper,
excelsior, or felt wadding next to the projectile so as to hold the
powder in contact with the primer, in some fixed ammunition a brass
diaphragm is soldered to the inside of the case for the same purpose
and to keep out moisture, (4.7” Gun). An igniting charge of black
powder is a part of the primer and in some cases an additional charge
is placed at the forward end of the powder space in the cartridge case
to insure rapid ignition of the smokeless powder. In this case it is
held in place between two quilted disks of crinoline.
=Semi-fixed ammunition= is employed in our 6” and 4.7” field howitzers.
The cartridge case contains three weights of propelling charge for
firing in the three zones designed to give a high angle of all with
these weapons. Access to the charge is had by tearing off the brass
diaphragm closing the forward end of the cartridge case. By removing
the first charge the remaining charge is that prescribed for the second
zone, and by removing the top two charges the remaining charge is that
of the first zone. The three charges are tied together and the middle
charge has an igniting charge of black powder attached. The removal of
charges is facilitated by the separate container for the powder charge
and the round is more easily handled in the two parts especially in the
case of the six-inch howitzer, where the projectile weighs 120 lbs.
The same primer is used as in fixed ammunition, the cartridge case
performing the function of an obturator.
[Illustration: BREECH MECHANISM OF 155 GUN SHOWING DE BANGE OBTURATOR.]
=Separate Ammunition.—Obturation.= The 155-mm Filloux gun and 155-mm
howitzer use separate ammunition. In such guns there must be provided
some form of a gas check which will prevent the powder gases from
rushing to the rear into the threaded portion of the breechblock, as
this would soon erode the thread sectors and render the gun useless
beside losing a large amount of pressure in the bore. The device
used as a gas check is called an obturator. There are two systems of
obturation in use, named after their inventors:
The DeBange and the Freyre. The former is used in the 155’s. It
consists of a steel mushroom head closing the rear of the powder
chamber, the spindle of which passes through a central hole in the
breechblock. Between the mushroom head and the face of the breechblock
is a pad of asbestos, paraffine and tallow, pressed into shape by a
hydraulic press and covered by canvas or asbestos wirecloth. Split
rings having hardened outer surfaces are fitted, one just behind the
mushroom head and one just in front of the face of the breechblock.
Their diameter is slightly greater in the free state than the conical
surface of the bore where they bear when the breech is closed so that
they always close the rear of the powder chamber. The pressure of the
powder gases forces the mushroom head to the rear and this compresses
the asbestos pad which in turn forces the split rings to bear with
greater force against the walls of the powder chamber thus securely
closing the rear opening of the powder chamber. For more details of
this device see pages 302 to 306 Tschappat’s O & G.
=Powder Bags.= Cartridge bags for separate loading are made of raw
silk, and are sewed with silk thread. Other materials are apt to
produce flare-backs or premature explosions because they are not
entirely consumed in the bore or continue to burn if not consumed.
The raw silk however either is entirely consumed or if not, the parts
ignited immediately go out as soon as the flame is removed and do not
smoulder. Specially treated cotton fibre bags have been tried but so
far as I know have not as yet superseded the raw silk for the purpose.
The gases remaining in the bore after the discharge of a charge of
smokeless powder are explosive and with air form an explosive mixture,
hence the danger upon opening the breech if any smouldering particles
remain in the bore.
[Illustration: _21 GRAIN PERCUSSION PRIMER MARK II-A_]
=Primers.= The devices for initiating explosions of propelling charges
in military guns are called primers. With fixed and semi-fixed
ammunition the primers are seated in the base of the cartridge case.
In the case of separate loading ammunition the primers are inserted
separately in the breechblock, the expanding gases of the detonated
primer forcing the walls of the primer case tightly against the bore
through the breechblock and thus sealing this channel of escape for
the gases from the powder chamber. This necessitates a much larger and
stronger case for separate loading primers than for those inserted in
the base of a cartridge case.
=Classes of primers.= Primers are divided into three classes according
to the method by which they are fired: (a) _friction primers_, (2)
_electric primers_, (3) _percussion primers_. Combination primers are
made which may be fired by any two of these methods, usually electric
and one of the others. The characteristics of a good primer are,
certainty of action, safety in handling, no deterioration in storage,
simplicity in construction and be cheap to manufacture. They are also
divided into obturating and non-obturating depending upon whether they
close the vent during discharge or not.
=Primer pressing.= Primers for fixed ammunition are inserted in the
base of the cartridge cases by means of a special press for this
purpose. The primer body is a trifle larger than the seat in the
cartridge case provided. This seat is rough bored to a diameter less
than the finished size and then mandreled to finished dimensions with
a steel tapered plug. This process toughens the material of the case
around the primer seat and prevents the expansion of the primer seat
under pressure of the expanding gases.
=Percussion primers.= Except for very heavy siege guns and railroad
artillery the guns handled by the Field Artillery use percussion
primers. The 110-grain percussion primer is the one in use in our
service and as typical will be described. The charge consisting of 110
grains of compressed black powder makes the charge burn like a torch
rather than explode, which facilitates the ignition of the charge of
smokeless powder, with which the flame comes in contact. The diametral
holes spray the flame in several directions thus insuring ignition
at many points simultaneously. The percussion element consists of a
percussion primer cup, the percussion composition and an anvil, all of
which are assembled together in a cup in the rear face of the primer
case. The percussion composition is made up of chlorate of potash,
sulphide of antimony, ground glass and sulphur. A blow upon the cap by
the firing pin detonates the percussion composition and the flame from
this detonation ignites the black powder which in turn explodes the
charge of smokeless powder.
The General Shape and Nomenclature of Projectiles.
The reason for the particular shape of shells may not be clear to
all. In the first place all matter has the property known as inertia,
which we may define as that tendency of matter to remain in a state
of rest or to continue at a uniform velocity if in motion. It offers
a resistance to any change in the state of either rest or motion
whether of amount or direction. Consequently when we apply a sudden and
tremendous force to the base of a projectile by means of the expansive
force of exploding powder gases, there will be set up in the metal a
resistance to this force in which every particle of the projectile will
resist by an amount proportional to the mass of particles beyond the
point of application of the force to itself. The actual force will be
proportional to the weight and acceleration produced by the applied
force in the projectile. This explains the reason why the _walls of
the projectile are thicker near the base_. It also explains the method
of calculating the thickness of walls, for if we know the weight at
any cross section and the co-efficient of strength of the metal we may
calculate the thickness of walls necessary to withstand the pressure
for any given muzzle velocity which is fixed by other considerations.
It explains also the preference for steel in projectiles as for the
same weight the steel is much stronger making it possible to throw a
greater amount of shrapnel or high explosives in shell.
[Illustration: _155-MM COMMON STEEL SHELL MK IV_]
The necessity for compact loading, especially in the case of high
explosive shell is also noted as otherwise the shock due to inertia
would break up the charge and perhaps cause a premature explosion.
Hence it is very necessary to guard against airholes in filling shell
cavities.
In order to secure regular and uninterrupted movement of the projectile
through the bore it is necessary that the projectile and bore have
the same geometric axis. Also the projectile must be seated exactly
and uniformly for succeeding rounds in its seating in the bore. This
latter is necessary in order that the powder chamber may not vary as
this would give irregular pressures. The liability of _strapping the
rotating bands_ or setting off the fuze in certain kinds of fuzes are
also explained by inertia. It might even cause sufficient shock to
detonate the charge in the shell. The remedy is accurate seating of
each projectile by reason of trained gun crews using the same amount
of force at each ramming. The first condition, coincidence of axes, is
obtained by means of the ogival head which has a diameter some tenths
of a millimeter smaller than the diameter of the bore, and serves as a
front support for the projectile while the rotating bands center it in
rear. Were it not for the bell the projectile, held only by the soft
material of the rotating band, would wabble in its travel through the
bore and tumble soon after leaving it. It is also necessary that the
center of gravity of the projectile be on its geometric axis. Otherwise
it will travel on a spiral of the same pitch as the grooves and knock
the tube walls as it travels through the bore and without the support
of the bell might cause a premature explosion by actuating the fuze.
[Illustration: _155M/M SHRAPNEL—95 LBS.—MARK-I._]
[Illustration: COMMON STEEL SHELL MARK I.
COMMON STEEL SHELL MODEL OF 1905.
SHRAPNEL.
CARTRIDGE CASE.
4.7” Gun Ammunition.]
Three-inch Ammunition.
=Fixed ammunition= is used in the 3” field guns, and is made up with
either common shrapnel, high explosive shrapnel, or common steel shell.
The rounds as made up vary in length with the type of projectile used.
The ammunition chests of the battery are of sufficient size to take
any one of the rounds furnished, so that the number of each kind to be
carried is a matter for regulation by proper authority. Each round is
issued with projectile filled and fused. The weight of the projectile
is 15 pounds, and the total weight of one round is 18.75 pounds. The
components of one round are _the cartridge case with primer, the powder
charge, igniter, projectile and fuze_.
=The cartridge case.=—The cartridge case is a solid drawn-brass case
10.8 inches long; it has a capacity of 66.5 cubic inches, and weighs,
with primer, 2.25 pounds. A circular groove is cut in the base of
the cartridge case and _the groove is painted red for high explosive
shrapnel, yellow for common shrapnel, and black for high explosive
shell_.
=The primer.=—The percussion primer, known as the “110-grain percussion
primer,” contains an igniting charge of 110 grains of black powder in
addition to the essential elements of a percussion primer. The purpose
of the black powder is to insure the ignition of the smokeless powder
charge in cartridge case.
[Illustration: _Common Steel Shell._
_Common Shrapnel._
_Cartridge Case._
_Semple Tracer._
_High Explosive Shrapnel._
3” AMMUNITION]
=The powder charge.=—The powder is a nitrocellulose powder composed
of multiperforated (7 perforations) cylindrical grains, each 0.35”
long and 0.195” in diameter. The charge varies slightly for different
lots of powder, but is approximately 24 ounces. The charge gives a
muzzle velocity for shrapnel of 1,700 feet per second (1600 f/s for
shell) with a maximum pressure in the bore not exceeding 33,000 pounds
per square inch. At the front end of the cartridge case there is an
igniter of black powder weighing about ¼ oz. which assists in the
uniform ignition of the smokeless powder charge.
=The projectiles.=—All projectiles have a copper rotating band 1.2”
from the base. This band engages in the rifling of the bore of the
piece, and gives the projectile a rapid rotation about its long axis
during flight. This causes it to travel straight, point on, without
tumbling.
=Common shrapnel.=—The common shrapnel is a base-charged shrapnel
fitted with a combination fuze. The case is of steel with solid base.
The shrapnel filling is composed of 252 balls, each approximately 167
grains in weight (42 to the pound). The balls are approximately 0.5” in
diameter. The balls are poured around a central tube and rest upon a
steel diaphragm, the interstices containing a smoke-producing matrix.
The bursting charge consisting of 2¾ oz. of black powder is in the
base and is covered by the diaphragm which supports the central tube,
affording a conduit to the flame leading from the fuze to the bursting
charge.
In action the case is not ruptured upon the explosion of the bursting
charge; the head is stripped and the balls are shot out of the case
with an increase of velocity of about 274 feet per second. The
remaining velocity of the shrapnel at 6,500 yards is approximately
724 feet per second and the time of flight 22 seconds, so that at
that extreme range, with the increase of velocity due to the bursting
charge, this shrapnel with 21-second fuze will be effective. The weight
of the shrapnel with fuze is 15 pounds.
Shrapnel is a projectile containing a great number of hardened steel
balls, each approximately ½” diameter, which may be projected from
a point in the air (called the _point of burst_) close to but short
of the target. Each ball is capable of killing a man or horse at
a distance up to 250 or 300 yards from the point of burst. Taken
collectively, the paths of these balls form a cone, called the _cone
of dispersion_. The ground section of this cone is elliptical in shape
with its longer axis approximately in the plane of fire. At mid-range
when burst at _normal height of burst_ (H. B. = 3 mils), the dimensions
of this area are approximately 20 yards wide by 250 yards deep. These
dimensions will however vary with the _angle of fall_, _the height
of burst_, the _slope of the ground_ at the target, and the relation
between the _linear_ and the _rotational velocities_ of the shrapnel at
instant of burst in the air. A 3-mil H. B. is chosen because this gives
an average density of 1 hit per square yard of vertical target area. An
infantry skirmisher (standing) with his interval occupies approximately
1 square yard.
Shrapnel has very little effect upon material objects. It is very
effective against personnel not protected by cover, or to search an
area which is known to be occupied, or which must be traversed, by
hostile troops.
_Ehrhardt High-explosive shrapnel._—The Ehrhardt high-explosive
shrapnel is fitted with a combination fuze and a high explosive head.
The case is drawn steel with solid base. The shrapnel filling is
composed of 285 balls, each approximately 138 grains in weight (50
to the pound). The balls are poured around the central tube and rest
upon the steel diaphragm, the interstices containing a matrix of high
explosive.
In time action (burst in air), the case is not ruptured upon the
explosion of the bursting charge, but the head is forced out and the
balls are shot out of the case with an increase of velocity of from 250
to 300 feet per second. In the meantime the head continues its flight,
detonating on impact.
If the fuze be set at “safety” or for a time greater than the actual
time of flight, this shrapnel may be used in lieu of high-explosive
shell. Upon impact a high-explosive shrapnel is detonated by means
of the percussion element of the combination fuze, the head being
detonated first, which detonation causes the sympathetic detonation of
high-explosive matrix surrounding the balls.
=Common steel shell.=—This steel shell is high-explosive and fitted
with a base detonating fuze. The case is hollow and made of drawn
steel. It is provided with an ogival head. The steel shell contains a
bursting charge of 13.12 ounces of Explosive D. The weight of the shell
with bursting charge and fuze is 15 pounds. The shell is always issued
filled and fuzed.
This shell bursts on impact and with great force exerted in all
directions. It is a powerful instrument for the destruction of material
objects such as guns, intrenchments, houses, stone walls, etc. The
effect, however, is very local.
=Frankford Arsenal combination fuzes.=—These fuzes are point fuzes with
combination time and percussion elements for use with common shrapnel.
They are of the type known as the ring or “dial” fuze, in which the
time train is set by turning a graduated ring which carries part of the
train. These fuzes may be reset as often as desired.
=Ehrhardt combination fuze for high explosive shrapnel.=—This fuze is
similar to the Frankford Arsenal Combination time and percussion fuze
but in addition contains a high explosive head and detonating element.
Due to this arrangement, both the projectile and the high explosive
head have a high-explosive shell effect when striking on impact.
=The service base detonating fuze.=—The details of the detonating fuze
and the composition of the detonator are kept secret. A detonating
fuze is necessary in order to produce a higher order of explosion by
causing an instantaneous conversion of the high explosive compound
called “Explosive D” with which the shell is charged. If an ordinary
percussion fuze were used only an ordinary explosion would be produced
as in the explosion of black powder.
=Preparation of blank metallic ammunition.=—Blank metallic ammunition
will always be assembled under the personal supervision of a
commissioned officer, who will be held responsible that it is prepared
in the manner prescribed. (G. O. 9, War Dept., Jan. 11, 1908.)
For this purpose there are issued blank-cartridge cases, black powder
in bulk, tight-fitting felt wads, rubberine, or other quick-drying
paint, primers, etc.
Before assembling, the cartridge cases should be carefully inspected to
see that they are in sound condition and thoroughly clean and dry. They
should also be tested by trying them in the gun, to determine whether
they have become deformed. Any cases that do not readily enter the
chamber in the gun or that are otherwise seriously deformed should be
laid aside for resizing. After inspecting the cartridge cases the blank
ammunition should be prepared as follows:
(a) Insert the primers with the primer-inserting press.
(b) Pour into the cartridge case the proper weight of black powder and
shake it down well.
(c) Insert the felt wad and press it down hard until it rests squarely
on the powder charge.
(d) Give the upper surface of the felt wad and the inside of the
cartridge case just above the wad a good coat of the rubberine or other
quick-drying paint furnished for the purpose, using a brush, and allow
the case to stand until this coat is dry. Then apply another coat of
rubberine paint in a similar manner. The object of using rubberine
paint, which is strongly adhesive, is to thoroughly seal the joint
between the wad and the case to prevent any powder grains from leaking
out, and at the same time to firmly hold the wad in place.
=The reloading and cleaning outfit.=—This outfit consists of the
following parts, and is furnished to each battery:
Primer-inserting press, small
Bushing
Powder measure, saluting
Decapping tool, with guide
Cleaning brush
Hammer
Case holder
Case-holder stand
Storage chest
The bushing is used in the primer-inserting press for the insertion of
new primers.
The decapping tool and case holder and stand are used for removing
exploded primers from the cartridge cases. A light blow on the rod with
a piece of wood or the bronze hammer generally removes the primer.
A powder measure to suit the saluting charge for the gun is furnished,
and when level full holds the required charge.
The cleaning brush is furnished for cleaning the cartridge cases after
they have been used and should be ordered to suit the size of case for
which intended.
=Care of Cartridge Cases.=—As soon after firing as practicable the
exploded primers should be removed from the cartridge case by means
of the decapping tools furnished with the reloading outfit. The case
should then be thoroughly washed in a strong solution of soft soap and
soda to remove all powder residue. It should then be thoroughly dried.
If the cartridge cases are carefully cleaned and washed immediately
after firing, not only will less labor be required but the life of the
cartridge case will be greatly prolonged.
A good solution for washing cartridge cases may be prepared by using
ingredients in the following proportions: 1 gallon of water, 2½ ounces
of soft soap, 5½ ounces soda. The mixture should be boiled and stirred
until the ingredients are entirely dissolved.
In washing cartridge cases this solution should be used hot and in
sufficient quantity to completely immerse the cases.
Neither acids nor solutions of acids will be used for cleaning
cartridge cases.
Precautions to be Observed with Fixed Ammunition.
(a) Do not unnecessarily expose ammunition to the sun or load it into a
warm gun before time for firing; if this is done, erratic shooting will
result.
(b) Handle carefully, otherwise cartridges may become deformed and
cause jams.
(c) Never use force or any implements on the base of the cartridge in
loading.
(d) See that fuzes set at safety or are provided with waterproof brass
cover for transport.
(e) Do not fire ammunition which has been under water with the
waterproof brass cover removed.
(f) Both service and blank ammunition should never be carried in the
battery at the same time. If conditions are such that both may be used
in exercises, only one kind should be in the firing battery; the other
should be under lock and key outside the firing position.
(g) Misfires and hangfires are of exceedingly rare occurrence. In case
of a failure to fire, the firing handle should be pulled again in order
to snap the trigger. If this fails to fire, the breech should _not be
opened_ until after the expiration of at least one minute, when the
round or cartridge should be removed and placed to one side. Defective
ammunition, cartridges and primers should be reported.
With Blank Ammunition.
Firing with blank ammunition will be greatly facilitated by a careful
observance of the following:
(a) Before firing, a careful examination should be made of the
assembled rounds to see that the felt wads have not become displaced
or the cartridge cases dented or deformed by careless handling.
If the cartridge cases have been properly resized and are clean,
no difficulty should be experienced in inserting them in the gun,
provided the chamber of the latter is clean. The continued insertion of
cartridge cases that are not clean causes an accumulation in the gun
chamber which may make the insertion of subsequent rounds difficult or
impossible.
(b) In firing blank ammunition the gun chamber will be sponged after
each round with a damp sponge, to extinguish sparks and remove powder
residue resulting from the previous round, before the insertion of
another round.
(c) Care will be taken to see that the sponges are not worn and that
they thoroughly fit the chamber. The interval between rounds in firing
blank ammunition should be sufficient to allow thorough sponging of
the chamber and examination to ascertain that all sparks have been
extinguished.
(d) Wads for the preparation of blank metallic ammunition are made to
tightly fit in the cartridge case. No wads should be used that are not
a tight fit in the case.
FUZES.
=Principle of operation.=—We have just learned something of the force
of inertia in connection with a projectile. Most fuzes are actuated
by this force. From our knowledge of the trajectory we know that
usually a projectile does not strike on its nose. Therefore we cannot
devise our fuzes to work like the driving of a nail into a board. The
striking element is the anvil and is a fixed pointed spur against
which a sliding element containing a fulminate strikes. The sliding
block carries a small charge of black powder which is set off by the
fulminate, thus igniting the train which leads to the high explosive
charge detonator. Were this sliding block left free to slide back and
forth at all times it would be unsafe to transport the fuze, as it
might be set off by accident. There must be therefore some means of
holding it safely away from the anvil until it is desired to detonate
the charge. There are thus two conflicting conditions to be met: safety
during transportation and sensitiveness at the point of departure.
It may not be understood at first why sensitiveness at the point of
departure should be a condition to be met. Suffice it to say that all
fuzes are designed to arm at discharge or soon after leaving the bore
for they must be ready to act at any time after leaving the muzzle.
Were they to be safe during flight they might be so safe that the
remaining velocity would not be sufficient to set them off. All fuzes
are designed to arm as we say either during travel through the bore or
immediately after.
Methods of Arming.
_Spring method._—Let us suppose that after our projectile has started
on its way the sliding block is free to move within a cavity at the
forward end of which is the anvil. If the projectile comes to a sudden
drop or even sudden reduction of velocity the block if unrestrained
will, according to the principle of inertia, keep on going till
something stops it. The something in this case is the anvil and the
fulminate cap is set off. But it is not so simple. For while the
projectile is in flight it is acted upon by the air resistance and
slows down but the block in the cavity of the head is not subjected to
this resistance. It therefore gains on the projectile or creeps forward
in the cavity unless restrained as it is by a spring. Now one more
point and this type of fuze is complete. We supposed that our block
was free to slide. For safety’s sake it is pinned to the cavity. Again
we call upon inertia to bread the pin so as to leave the block free
to slide. The strength of the pin is calculated so that the force of
inertia of the mass of the block is greater than the resistance of the
safety pin and when the projectile starts the pin breaks and the spring
forces the block to the rear of the cavity until the sudden stop of
the projectile permits the block to slide forward as explained. Such a
fuze requires a comparatively high initial velocity and is not adapted
to howitzers using low muzzle velocities.
There are three other methods in use to arm the fuze. They are =inertia
of a sleeve=; =centrifugal force= and =powder pellet system=, that is,
combustion of a grain of powder holding the sliding block from the
anvil by means of an arm resting against the unburned powder grain.
These are more sensitive than the type described.
=In the first system=, a sleeve fitting around the plunger carrying
the cap slides to the rear by inertia when the projectile starts and
two clips engage in notches on the plunger body making the sleeve and
plunger thereafter move as one body, they are thus held together by
a plunger spring which before arming held the plunger away from the
anvil. The safety spring held the sleeve and plunger away from the
anvil and after arming prevents forward creeping by the plunger and
sleeve now locked together. Upon striking, the plunger and sleeve move
forward as one body and the cap strikes the anvil.
=In centrifugal systems= the primer plunger is kept safely away from
the anvil by a lock which is kept in place by springs. When the
rotational velocity reaches a certain point the force of the springs
is overcome by the centrifugal force and the locks are thrown aside or
opened and the plunger is free to move forward on impact.
=In the powder pellet system= (the one largely used by the Germans)
there is a well or channel filled with compressed powder, this is set
off by a fulminate cap which is fired by inertia, a small plunger-anvil
striking the cap. When the powder is consumed it leaves a channel
into which an arm attached to the sliding block carrying the igniting
fulminate for the charge may slide, thus permitting the block to slide
forward to the anvil fixed in the forward part of the cavity. It is
held from creeping forward after the compressed powder is burned by a
safety spring, thus insuring sufficiently hard an impact to set off the
cap.
Heretofore in our service the fulminating cap has been fixed and the
plunger carried the anvil or as we call it the firing pin. Such is now
the system in our base detonating fuzes, and in our combination fuze.
The new point detonating fuzes are patterned after the French and are
practically French fuzes.
Fuzes Classification.
Fuses are classified as:
(a) Percussion if it acts on impact, producing a low order of explosion.
(b) Time when it acts in the air at a certain point of the trajectory.
(c) Combination if it is able to act in the air or upon impact.
(d) Detonating when it contains a fulminate which will bring about
detonation upon impact.
The detonator may be separate or incorporated in the fuse. For the
75-mm gun and the 155-mm howitzer it forms a part of the fuze.
Many fuzes are armed on set-back. An exception to this is the long
detonating fuse, MK 111, which is armed by the unrolling of a brass
spiral holding together two half rings made of steel so fitted as to
prevent the anvil and the head of the fuse from getting close together.
The spiral unrolls when the rotational velocity of the projectile
reaches a certain speed, thus drawing away the two steel rings and
arming the fuse.
[Illustration: _DETONATING FUZE—MARK-III._]
[Illustration: _DETONATING FUZE—MARK-V._]
It is of great importance that the spiral spring be not unrolled during
transportation or storage. This is prevented by winding a tape of
tarred canvas around the spirals, the head being covered by a thin
band of tinfoil. Just before loading the projectile the head and tape
are removed by pulling the free end of the tape.
The following precautions concerning fuses must be rigidly observed to
prevent grave accidents:
1. All detonators and detonating point fuses must be fitted with a felt
washer underneath, thus insuring proper seating in the central tube.
2. Never disassemble a fuse by unscrewing.
3. Any fuse, the parts of which have become accidentally unscrewed,
must be destroyed at once. If fired it may cause a premature burst; if
handled a grave accident may result.
4. Any fuse or projectile which has been fired is dangerous, because it
may then be able to detonate by a very slight shock. It is forbidden to
touch it.
5. Never remove the tin hood from the long fuse before having screwed
the fuse in the central tube.
6. After having removed the tin hood, be sure that the spiral is in its
proper position. Never use a long fuse without the spiral.
7. Be sure the men understand that this spiral must not be removed. It
has happened that men have removed this spiral, thinking that it was a
device similar to the safety ring in trench mortar fuzes, MK VII E.
8. See that the ring of the long fuze which connects the powder train
to the fuze body cannot be unscrewed. If it can be unscrewed the fuze
should be sent back to the depot.
9. If it is necessary to remove a shell with a long fuze by means of
the rammer, be sure to have a special rammer cup in the shape of a
hollow cylinder of wood which will fit between the shell and the rammer.
10. Time and combination fuzes cannot be made absolutely water-tight;
the cover must therefore not be removed until the projectile is about
to be loaded.
Fuse Tables.
Tables showing American and French fuses to be used by our Field
Artillery, with information concerning markings, color, time of delay,
size of fuse, etc.
DETONATING FUSES.
—————————————————————————————+——————————————————————+—————————————
Time of delay. | Color. |Size of Fuse.
—————————————————————————————+——————————————————————+—————————————
MK I 2-100| White head. | Short.
| |
M II (non delay) 2-100| |
MK II (non delay) 2-100| White top. | Short.
MK II (short delay) 5-100| Black top. | Short.
M II (long delay) 15-100| Black head. | Short.
MK III (Supersensitive) zero| No color. | Long.
| |
| |
| |
MK IV (non-delay) 2-100| White top. | Short.
MK IV (short delay) 5-100| Black top. | Short.
MK IV (long delay) 15-100| Black top violet | Short.
| detonator socket. |
MK V (non-delay) 2-100| White top. | Short.
| |
MK V (short delay) 5-100| Black top. | Short.
| |
Mark—VII (non delay) 2-100 | White. | Short
Mark VII (long delay) 20-100| Black top with violet| Short
| detonator socket |
—————————————————————————————+——————————————————————+—————————————
—————————————————————————————+——————————————————+———————————————————
Time of delay. |Corresponding to. | Cannon.
—————————————————————————————+——————————————————+———————————————————
MK I 2-100| Russian 3GT. | 3” gun for target
| | practice only.
M II (non delay) 2-100| | 8”, 9.2”,
MK II (non delay) 2-100| | 204-m/m.
MK II (short delay) 5-100| Modified. | Gun and Howitzer.
M II (long delay) 15-100| Russian. |
MK III (Supersensitive) zero| French IAL. | 75 G; 3.8”G and H;
| | 4.7 in. G and H
| | 6”H; 155H; all
| | gas shells.
MK IV (non-delay) 2-100| French 24/31 | Howitzer only.
| SR (99-15). |
MK IV (short delay) 5-100| French 24/31 | Howitzer only.
| AR (99-15). |
MK IV (long delay) 15-100| French 24/31 | Howitzer only.
| SR (99-15). |
MK V (non-delay) 2-100| French 24/31 | All guns, but not
| SR (99-08). | Howitzers.
MK V (short delay) 5-100| French 24/31 | All guns, but not
| AR (99-08). | Howitzers.
Mark—VII (non delay) 2-100 | | 6” T. M.
Mark VII (long delay) 20-100| | 6” T. M.
| |
—————————————————————————————+——————————————————+———————————————————
Letter “E” after mark VII indicates safety device.
Note:—All American point detonating fuses are stamped on head cap in
letters and figures, .125 in high, with name of use, amount of delay,
initials of loader, lot and number; thus: PDF. MIV, xx Delay, FA,
Lot No. xx.
[Illustration: 45-SECOND COMBINATION FUZE MARK I.]
[Illustration: _21 SECOND COMBINATION FUZE MODEL OF 1907 M._]
COMBINATION FUSES.
—————————————————————————+——————————+—————————————————————
|Total time|
Fuse. | burning | Corresponding
| Sec. | French Type.
—————————————————————————+——————————+—————————————————————
21 s/comb. F. A., 1907 M.| 21 | 22/31M 1897, 24 sec.
21 s/comb. F.A., 1915 | 21 | 22/31M 1916, 24 sec.
| | AA.
31 s/comb. F. A. 1915 | 31 | 30/55M 1889, 40 sec.
45 s/comb. F. A. 1907 M. | 45 | Same as above.
| | 30/55M 1889, 40 sec.
| | 30/55M 1913, 40 sec.
| | AA.
—————————————————————————+——————————+—————————————————————
——————————————+————————————————+——————————————————+———————
Fuse. | On what | By what cannon | Wt. of
|projectile used.| fired. | fuse.
——————————————+————————————————+——————————————————+———————
21 s/comb. | | |
F. A., 1907 M.| Com. Shrapnel. | All 3” and 75-mm | 1¼ lbs.
21 s/comb. | MKi. | guns |
F.A., 1915 | Com. Shrapnel. | All 3” and 75-mm | 1¼ lbs.
31 s/comb. | MKi. | guns |
F. A. 1915 | Com. Shrapnel. | 4.7” gun. | 2 lbs.
45 s/comb. | | |
F. A. 1907 M. | | |
| Com. Shrapnel. | 155 How. |
| MKi. | |
| C. S. Shell AA | 4.7” gun |
| MKiii | Anti-aircraft. |
| AA. Shrapnel. | |
——————————————+————————————————+——————————————————+———————
ACTION OF AMERICAN AND FRENCH DETONATING FUSES.
———————————+——————————+————————————————————+———————————
Time | zero | 1/100 | 2/100
Color | No color.| Red. | White.
| | |
American | MKii | None being made. | MK i
Detonating | | Fuse is considered | MK ii (ND)
| | unsafe | MK iV (ND)
| | safe | MK iV (ND)
Fuses | | Will be abandoned |
| | by French | MK V (ND)
French | iAL. | 1 | SR.
detonating | | |
fuses | | |
———————————+——————————+————————————————————+———————————
———————————+————————————+———————————————
Time | 5/100 | 15/100
Color | Black. | Black with
| | violet socket.
American | MK ii (SD) | MK ii (LD)
Detonating | MK ii (SD) | MK iv (LD)
| MK V (SD) |
| MK V (SD) |
Fuses | |
| |
French | AR. | LR.
detonating | |
fuses | |
———————————+————————————+———————————————
Notes on Ammunition Marking.
=Marks on H. E. Shell.= These are of two kinds.
(a) Stamped marks made with a steel punch on the body of the projectile
just above the rotating band. These refer to the manufacture of the
projectile.
(b) Painted marks or bands which are clearly visible. They refer to the
loading, to the weight of the projectile and to the special purposes
for which the projectile is to be used.
Painted marks referring to loading are found on the ogive.
H. E. shells are usually painted red.
Marks referring to weight are painted in black just above the rotating
band, as follows:
L.—very light.
+—light.
++—normal.
+++—heavy.
++++—very heavy.
A white cross above these marks means that a plate has been welded on
the base. These marks are also painted on the boxes.
Shells fitted with cartridge cases (fixed ammunition) are not painted
below the rotating bands.
Special Shell.
Incendiary shells.—These incendiary shells are filled with some
flame-producing liquid, alumino thermic charge or incendiary cylinder
composed of slow burning linstock and string strongly impregnated with
saltpeter.
Markings.—Green with red ogive.
All shells containing black powder are more or less incendiary.
Percussion shrapnel is incendiary.
[Illustration: 75-mm Ammunition.]
Star Shells.—For 155 howitzer. Upon bursting, they liberate eight
white stars fitted with silken parachutes. The stars are projected
backward through the base of the projectile at the point of burst.
The parachutes open, the stars descending very slowly, illuminating the
surrounding objects for about 45 sec. The best height of burst is about
300 m.; the burst interval should not be over 300. These shells are
also incendiary. Markings: a blue star and an “E.”
Gas shells are either toxic or tear-producing.
(a) Toxic shells are numbered either 4 or 5. The liquids 4 and 5
volatize, immediately upon contact with the air. The gases are quickly
diffused and easily carried by the wind.
Effect.—Liquid 4 acts immediately and is felt instantly.
Liquid 5, on the contrary, works more slowly and its effects are
apparent only after several hours. Markings: Green with white bands,
and numbers 4 or 5 on the ogive.
(b) Tear shells.—These shells are numbered 11, 12 and 13. They are
filled with two liquids, either mixed or separated, one liquid being
tear producing, the other smoke producing. When the shell bursts,
a greater part of the liquid is volatilized, the remainder being
projected to the ground in small drops which volatize with variable
speed. Markings: Green with numbers 11, 12 or 13 on the ogive.
Tracer shell.—This shell is fitted with a time fuse which ignites
the inside charge, the flames of which pass through the holes in the
ogive thus tracing the trajectory. Tracer shells are used in fire for
adjustment on aircraft. They are also incendiary. Markings: White with
blue ogive. Letter “T” painted on body.
PRECAUTIONS IN SEPARATE LOADING PROJECTILES.
All projectiles must be seated accurately and carefully in loading,
otherwise not only inaccurate fire will result but also premature
detonations may occur.
Rotating bands should be smoothed and lightly greased just before
loading. In transport and in storage the bands should be protected by
rope bands, straw tithes, etc., to prevent deformation.