During the last forty years leading chemists have continued to
experiment with a view to the production of a gunpowder which should be
smokeless. But not until the last few years has any considerable degree
of success been attained.
To be smokeless, a gunpowder must yield only gaseous products of
combustion. None of the so-called smokeless powders are entirely
smokeless, although some of them are very nearly so.
The smoke of common black gunpowder is largely due to minute particles
of solid matter which float in the air. About one-half of the total
products of combustion of black gunpowder of ordinary composition
consists of potassium carbonate in a finely divided condition and of
potassium sulphate, which is produced chiefly by the burning in the air
of potassium sulphide, another production of combustion, as on the
outrushing gases it is borne into the air in a fine state of division.
Another cause for the smoke of gunpowder is the formation of small
liquid vesicles which condense from some of the products of combustion
thrown into the air in a state of vapor, in the same manner as vesicles
of aqueous vapor form in the air on the escape of highly heated steam
from the whistle of a locomotive.
Broadly speaking, an explosive compound is one which contains, within
itself, all the elements necessary for its complete combustion, and
whose heated gaseous products occupy vastly more space than the original
compound. Such compound usually consists of oxygen, associated with
other elements, for which it has great affinity, and from which it is
held from more intimate union, or direct chemical combination, under
normal conditions, by being in combination as well with other elements
for which it has less affinity, but which it readily gives up for the
stronger affinities when explosion takes place, the other elements
either combining with one another to form new compounds or being set
free in an uncombined state.
An explosive is said to detonate when the above changes take place
instantaneously, the action being transmitted with the speed of
electricity by a sort of molecular rhythm from molecule to molecule
throughout the entire substance of the compound.
An explosive is said to explode when the above changes do not occur
instantaneously throughout the whole substance, but whose combustion
takes place from the surface inward of the particles or grains of which
it is composed, thus requiring some definite lapse of time.
The elements of an explosive compound may be associated chemically as in
nitro-glycerine and gun-cotton, which are chemical compounds, being the
results of definite reactions. Or, an explosive may be a mere mechanical
mixture of different substances comprising the necessary elements, as is
ordinary black gunpowder, which is a compound of charcoal, sulphur and
saltpeter, the saltpeter supplying the necessary oxygen.
No gunpowder can be smokeless in which saltpeter or any oxygen-bearing
salt having a metallic base is employed, for when the salt gives up its
oxygen, the base combines with other elements to produce a sulphate, a
carbonate, or other salt, which, being solid, produces smoke. Therefore,
to be smokeless, a gunpowder must contain no other elements than oxygen,
hydrogen, nitrogen, and carbon, and in such proportions that the
products of combustion shall be wholly gaseous. The nitric
ethers--gun-cotton and nitro-glycerine--constitute such explosive
compounds. These substances were formerly thought to be
nitro-substitution compounds, but are now known to belong to the
compound ethers of nitric acid.
Gun-cotton, discovered by Schonbein, in 1845, has since been looked upon
as the most promising material for a smokeless gunpowder, it being a
very powerful explosive and burning with practically no smoke. To-day,
gun-cotton, in some form or other, constitutes the base of substantially
all of the smokeless powders with which have been attained any
considerable degree of success.
Gun-cotton alone and in its fibrous state has been found to be too
quick, or violent, for propulsive purposes, such as use in firearms; as
under such conditions of confinement it is very likely to detonate and
burst the gun. However, if gun-cotton be dissolved in a suitable
solvent, which is capable of being evaporated out, such as acetone, or
acetate of ethyl, which are very volatile, it becomes, when thus
dissolved and dried, a very hard, horn-like, amorphous substance, which
may be used for a smokeless gunpowder. But this substance taken alone is
very difficult to mould or granulate, and the loss of expensive solvents
must necessarily be quite considerable.
When gun-cotton is reduced to a collodial solid, as above, and used as a
smokeless gunpowder, the grains must be made comparatively small to
insure prompt and certain ignition, and consequently the pressures
developed in the gun are apt to be too great when charges sufficiently
large are used to give desired velocities.
If, however, a compound be made of gun-cotton and nitro-glycerine, in
about equal parts, by means of a volatile solvent or combining agent,
such as one of the before mentioned, and the solvent evaporated out, we
obtain practically a new substance and one which, as regards its
explosive nature, is quite unlike either of its two constituents taken
alone. The nitro-glycerine, furthermore, being itself a solvent of
gun-cotton, much less of the volatile ether is necessary to render the
compound of an amorphous character. Being quite plastic this substance
may be wrought or moulded into any desired size or form of grain.
This simple compound of nitro-glycerine and gun-cotton, or with some
slight modifications, has been found, when properly granulated, to be
the most smokeless powder that has yet been discovered or invented. If
pure chemicals are employed in the manufacture, and the gun-cotton and
nitro-glycerine be made of the highest nitration and best quality, we
have a smokeless powder which will possess the following desirable
qualities:
1st. It is absolutely smokeless, that is, its products of combustion are
entirely gaseous.
2d. Its products of combustion are in no way deleterious or unpleasant.
3d. It is perfectly safe to manufacture, handle and transport. There is
no more danger of its exploding accidentally than there would be of an
explosion of shavings or sawdust; for, unless well confined and set off
with a strong primer, it will not explode at all. In the open its
combustion is so slow as to in no way resemble or partake of the nature
of an explosion.
4th. It is perfectly stable, and will keep any length of time absolutely
without undergoing any change whatever, under all conditions of
temperature or exposure to which gunpowder would ever be subjected.
5th. It is not hygroscopic, and may be soaked in water without being at
all affected by it.
6th. It will not corrode the cartridge case.
7th. It will not foul the gun.
8th. It is sure of ignition with a good primer, and may be made to burn
as slowly as desired by varying the character and size of the grains.
Indeed, it may be made to burn so slowly as to fail of complete
combustion before the bullet leaves the gun, and after firing several
rounds, partly burned pieces of the powder may be picked up in front of
the gun.
9th. In a shoulder arm, a velocity of 2,000 feet per second may be
imparted to the bullet with this powder, and with a pressure in the
chamber of the gun of not more than fifteen English tons. This is, of
course, when the gun, cartridge case, primer, and projectile are adapted
to the use of smokeless powder, and the granulation of the powder is
adapted to them.
If what I have here claimed for the above smokeless powder be true, it
would appear that it may be taken as really an ideal smokeless powder.
Why, then, has it not already been universally adopted? Surely such a
powder is just what every government is seeking. In reply to this, let
me say that, in order for the above compound to be an effective and
successful smokeless powder, with the manifestation of the many
desirable qualities which I have recited, a great many other conditions
are necessary, some of which I will mention. To arrive at the knowledge
that this compound would constitute the best smokeless powder has
required a great deal of experimenting. It was first thought that
gun-cotton colloid, without any nitro-glycerine, that is, gun-cotton
dissolved and dried, would burn more slowly, keep better, and give
better ballistics than it would if combined with nitro-glycerine. It was
also thought that gun-cotton of a high degree of nitration when made
into colloidal form would even then burn too quickly to be suitable for
use in firearms. Consequently, the first experiments were with low grade
gun-cotton, what is called collodion cotton, such as is employed in the
manufacture of celluloid. But, as this would not explode without the
addition of some oxygen-bearing element, various oxygen-bearing salts
were combined with it, such as nitrate of potassium, nitrate of ammonia,
nitrate of baryta, etc. Also a great many of the first smokeless powders
were made of low grade gun-cotton combined with nitro-glycerine in
varying proportions. These powders would often give very good results
when first made; but low grade gun-cotton or di-nitro-cellulose, as it
is called, is a very unstable compound, and these powders, after giving
very promising results, were found to be constantly undergoing change,
sooner or later resulting in complete decomposition.
When nitro-glycerine was first combined with gun-cotton in small
quantities, camphor was often added, to lessen the rapidity of
combustion which the nitro-glycerine was supposed to impart and also to
render the compound more plastic, and to tend to prevent the
decomposition of the low grade gun-cotton. But camphor being volatile,
would, by its evaporation, cause the powder to constantly change in
character. Castor oil has been found to be a better diluent, as this
will not evaporate.
As all of the smokeless powders made of a low grade gun-cotton were
found to deteriorate and spoil, experiments were made with gun-cotton of
the highest degree of nitration, both alone and in combination with
nitro-glycerine. These experiments were first conducted in England by
private parties and by the British government, when it was found that
high grade gun-cotton would give excellent results if made into a
colloidal solid and used alone, or in combination with certain other
constituents. With a view to saving the large quantity of solvents
necessary to reduce the gun-cotton, and to get a more prompt and certain
ignition with a larger grain, experiments were cautiously made by the
admixture of varying proportions of nitro-glycerine to the gun-cotton
when dissolved, or rather along with other solvents in the process of
dissolving it.
It was soon found that nitro-glycerine added in quantities, even equal
in weight to the gun-cotton itself, did not materially increase the
rapidity of the explosion of the compound. And it was also found that
high grade gun-cotton, when combined with nitro-glycerine, gave very
much better results than low grade gun-cotton.
I have spoken here of high and low grade gun-cotton, when in fact the
word gun-cotton should be applied only to the highest nitro-compound of
cellulose. The word gun cotton has always been rather loosely used.
Pyroxyline would be a better word, as this applies to all grades. When
cotton fiber is soaked in a large excess of a mixture of the strongest
nitric and sulphuric acids, gun-cotton proper, or that of the highest
grade, is produced. When weaker acids are used, lower grades of
nitro-cellulose are formed.
The first mentioned or highest grade gun-cotton, when thoroughly freed
from its acids, has always proved to be a perfectly stable compound. The
lower grades have always been found to be unstable and subject to
spontaneous decomposition. Nitro-glycerine has also been erroneously
thought to be a very unstable compound. But experiments have proved
that, when made pure, it is perfectly stable.
Having now explained how the knowledge came to be arrived at that the
aforementioned compound of highest grade nitro-glycerine and highest
grade gun-cotton would constitute the best basis for a smokeless powder,
I will now mention a few of the other conditions necessary to success
with its use, without assuming that smokeless powder has yet passed its
experimental stage, and is beyond further improvement. Nevertheless,
such is the compound which has come to stay as the basis of all
smokeless powders; and any smokeless powder, if a successful one, may be
counted upon as being made of this compound of gun-cotton and
nitro-glycerine, or of a colloid of gun-cotton, either alone or combined
with diluents, oxygen-bearing salts, or inert matter. The fact that
smokeless powder may still be said to be in somewhat of an experimental
stage is not to admit that it is not a success. Firearms, cartridge
cases, and projectiles are also still in an experimental stage, for they
are constantly being improved; yet their use has been a great success
for a good many years.
The question of success of a smokeless powder does not rest alone with
the powder itself. The gun, the cartridge case, primer, and bullet have
been as much the subjects of experiments in adapting them to the use of
smokeless powder as has the smokeless powder in being adapted to them.
To impart a velocity of 2,000 feet per second to a rifle ball, with
corresponding long range and accuracy of flight, has been a question as
much of improvement in rifles and projectiles as in the powder. To give
a velocity of 2,000 feet per second to a bullet, requires a pressure of
at least 15 English tons in the chamber of a gun. This would be a
dangerous pressure in an old-fashioned shoulder arm; while a bullet made
only of lead would strip on striking the rifling and pass right through
the barrel of the gun without taking any rotary motion whatever. It
might at first seem that the powder is the only thing to be considered;
but high ballistics can only be obtained when everything else is adapted
to its use.
The projectile, the cartridge case, the fulminating cap, and the gun
have had to be all built up together, and a very large amount of
experimenting has been necessary to determine what would constitute the
best projectile, best cartridge case, best fulminating cap, and what
should be the character of the rifling and the quality and temper of the
steel of the gun barrel.
It has been necessary first to conduct experiments to test the smokeless
powders for velocities and pressures, and then with the powders test
various kinds of projectiles and guns. In order to obtain the high
ballistics which have been secured, it has been found necessary to cover
the bullet with something harder than lead and to rifle the gun in a
special manner.
The French, who were the first to definitely adopt smokeless powder,
were the first also to make a rifle, projectile, cartridge case and
primer suited to its use.
To obtain long range with a small long bullet such as is now used, it
should rotate at a very high speed. It is well known to artillerists
that a projectile of four or more calibers in length has to be rotated
at a much higher speed than one of half that length, in order to keep
the projectile stiff in the air, and to prevent it from ending over in
its flight. To communicate this very high rotary movement to the bullet
in the instant of time during which it is passing through the barrel,
the rifling of the gun has to exert an enormous torsion on the bullet.
Lead, no matter how hardened, is not sufficiently strong, as it will not
only strip and pass straight through the gun without taking any rotary
movement whatever, but under such very high pressures it behaves like
wax, and is thrown from the gun in a distorted mass.
The French cover their bullets with German silver, a substance made of
nickel, zinc and copper; and in order to put as little strain upon the
rifling and projectile as possible, the rifling of the gun is made with
an increasing twist, and has no sharp edges. The French rifle is made
very strong at the breech and is of tempered steel throughout. In this
way the French have made smokeless powder a success--a smokeless powder
made substantially of a character such as I have herein described. With
smokeless powder, the French rifle imparts a muzzle velocity of 2,000
feet per second to the bullet, with a range of about 2,400 meters.
If smokeless powder be divided into sufficiently small grains to be
ignited by an ordinary fulminating cap, it would burn too quickly,
thereby causing the pressure to mount too high, and without giving the
desired velocity. Consequently very large and strong fulminating caps
have to be employed. Smokeless powder is not ignited in the same manner
as black powder. Something besides ignition is necessary. Black powder
simply requires to be set on fire; while a smokeless powder, on the
contrary, not only requires that it be set on fire, but that a certain
degree of pressure be set up inside of the cartridge case. For instance,
if a primer of a certain size should be found to operate perfectly well,
giving prompt ignition in the cartridge case of a rifle of small
caliber, it would be found that the same primer would not ignite a
charge of the same powder if loaded into a gun of one inch caliber. In
the latter case a few grains only lying near the primer would be
ignited, and these would soon become extinguished by sudden release of
pressure bringing about a cooling effect due to expansion of the gases.
In small cartridges a large fulminating cap is all that is required, but
in large cartridges it is necessary to resort to additional means of
ignition.
In France, where experiments were conducted with a 37 millimeter Maxim
gun, it was found to be impracticable to use a fulminating cap
sufficiently large to ignite the powder and cause it to burn. Therefore,
a small ignition charge of black powder was employed, it being put in a
capsule or bag and placed next the primer. On firing at the rate of 300
rounds per minute, the black powder, though small in quantity, produced
a cloud of smoke through which it was quite impossible to see. The
inventor of the gun then prepared for the French some wafers of
pyroxyline canvas, which were placed next to the primer, securing
thereby prompt ignition without the production of any smoke.
Smokeless powder, made as I have described, cannot be detonated by a
fulminating cap of any size or by any means whatever. A large charge of
fulminate of mercury placed inside the cartridge case next the primer
will not detonate the powder, it serving only to ignite it and cause it
to explode. But even this would not cause the powder to explode except
it be confined behind a projectile, that sufficient pressure may be run
up to make it burn in its own gases.
Some curious experiments with smokeless powder may be tried with a shot
gun. If the fulminating cap be large, the powder fine, the wads numerous
and hard and the charge of shot heavy, all being well rammed down, and
the paper case well spun over the last pasteboard wad, a charge of
smokeless powder about equal in weight to one-half of what would be
employed of black powder would give about the same results as black
powder. But if the charge of shot be omitted, the primer will only
ignite the powder, and there will be set up sufficient pressure merely
to throw the wads about half way up the barrel of the gun, when the
powder will go out. Now if this same charge of powder be collected and
reloaded into a new cartridge case and well confined behind wads and a
charge of shot, as above explained, it will all burn, giving the same
results as black powder.
Attempts have been made to use this powder in pistols and revolvers, but
here it has proved a failure, as the pressure is not great enough to
cause the powder to be consumed, unless it be in the form of very fine
grains or dust, in which case the pressure mounts too high. However,
this might be overcome to a degree by making the powder porous. The
chemical conditions of the powder might be the same, but the physical
conditions must be different. A powder suitable for shot guns and
pistols would not be suitable for rifles.
One not familiar with the characteristics of smokeless powder would be
almost certain to fail in his first attempt to fire it. Many persons
have been convinced by their first experiments that this powder would
not burn at all in a gun, any more than so much sand.
Smokeless powder is consumed with a rapidity which accords with the
conditions of its confinement. Therefore, the bullets which have been
experimented with by different governments have been the cause of much
of the varying pressures attributed to the smokeless powders.
The Austrians use the Mannlicher steel jacketed bullet. The steel casing
or jacket is first tinned on the inside and then the lead is cast in,
thus melting the tin and adhering firmly to the jacket. This projectile
sets up enormous friction in the barrel of the gun when used with
smokeless powder; as the smokeless powder leaves the gun barrel
perfectly clean and the two steel surfaces being in absolute contact
cause tremendous friction; and as the coefficient of friction varies
with every shot, the pressure in the gun constantly varies greatly.
The German silver covered bullet used by the French has the disadvantage
that when firing rapidly the chamber of the barrel becomes nickel plated
and great friction is caused, mounting up the pressures and causing the
muzzle velocities to fall off.
The Austrians, in order to prevent their steel cased bullets from
rusting and to lessen the friction in the barrel of the gun, cover them
with a heavy lubricant, which gives the cartridges an unsightly
appearance and causes them to gather dust and sand. The French employ a
lubricant at the base of the projectile, with a small copper disk
between the same and the powder.
Col. A.R. Buffington, commander of the National Armory at Springfield,
Mass., has made a steel covered projectile which he prevents from
rusting by blackening by a niter process. Several grooves are pressed in
the base of the bullet which carry a lubricant, and when the bullet is
inserted in the cartridge case the grooves are covered by it.
Furthermore, these grooves prevent the lead filling from bursting
through the steel casing, leaving the latter in the barrel, as often
occurs with the Austrian and French projectiles when using smokeless
powder.
A new projectile has lately come out, the invention of Captain Edward
Palliser, of the British army. This bullet consists of a jacket made of
very soft Swedish wrought iron, coated with zinc and filled with lead,
the lead being pressed into this jacket. The bullet is corrugated at its
base, after the manner of the one made by Colonel Buffington. This
projectile has been experimented with very extensively by the British
government, and at the works of the Maxim-Nordenfelt Guns and Ammunition
Company, in England. The zinc coating of the bullet is too soft to stick
to the barrel of the gun, and also in a measure acts as a lubricant.
This projectile has given better results than any other that has been
experimented with. The great velocities and the most uniform pressures
by the use of smokeless powder have been attained with this Palliser
bullet.