Nitro Explosives: A Practical Treatise by P. Gerald Sanford

P >> P. Gerald Sanford >> Nitro Explosives: A Practical Treatise

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23

For the .303 rifle .0375 inch diameter.
" 12 Pr. B.L. gun .05 "
" " .075 "
" 4.7-inch Q.F. gun .100 "
" 6-inch Q.F. gun .300 "
" heavy guns .40 to .50 "

For rifles the cordite is used in bundles of sixty strands, in field-guns
in lengths of 11 to 12 inches, and the thicker cordite is cut up into
14-inch lengths. Colonel Barker says that the effect of heat upon cordite
is not greater as regards its shooting qualities than upon black powder,
and in speaking of the effect that cordite has upon the guns in which it is
used (R.A. Inst.) said that they had at Waltham Abbey a 4.7-inch Q.F. gun
that had fired 40 rounds of black powder, and 249 rounds of cordite (58
per cent. nitro-glycerine) and was still in excellent condition, and
showed very little sign of action, and also a 12-lb. B.L. gun that had
been much used and was in no wise injured.

[Footnote A: The gun-cotton used contains 12 per cent. of soluble
gun-cotton, and a nitrogen content of not less than 12.8 to 13.1 per cent.]

[Illustration: Fig. 37 Scale, 1 inch = 1 foot. Single Strand Reel.]

[Illustration: FIG. 38.--"TEN-STRANDING."]

In some experiments made by Captain Sir A. Noble,[A] with the old cordite
containing 58 per cent. nitro-glycerine, a charge of 5 lbs. 10 oz. of
cordite of 0.2 inch diameter was fired. The mean chamber crusher gauge
pressure was 13.3 tons per square inch (maximum 13.6, minimum 12.9), or a
mean of 2,027 atmospheres (max. 2,070, min. 1,970). The muzzle velocity
was 2,146 foot seconds, and the muzzle energy 1,437 foot tons. A gramme of
cordite generated 700 c.c. of permanent gases at 0 deg. C. and 760 mm.
pressure. The quantity of heat developed was 1,260 gramme units. In the
case of cordite, as also with ballistite, a considerable quantity of
aqueous vapour has to be added to the permanent gases formed. A similar
trial, in which 12 lbs. of ordinary pebble powder was used, gave a
pressure of 15.9 tons per square inch, or a mean of 2,424 atmospheres. It
gave a 45-lb. projectile a mean muzzle velocity of 1,839 foot seconds,
thus developing a muzzle energy of 1,055 foot tons. A gramme of this
powder at 0 deg. C. and 760 mm. generates 280 c.c. of permanent gases, and
develops 720 grm. units of heat.

[Footnote A: _Proc. Roy. Soc._, vol. lii., No. 315.]

In a series of experiments conducted by the War Office Chemical Committee
on Explosives in 1891, it was conclusively shown that considerable
quantities of cordite may be burnt away without explosion. A number of
wooden cases, containing 500 to 600 lbs. each of cordite, were placed upon
a large bonfire of wood, and burned for over a quarter of an hour without
explosion. At Woolwich in 1892 a brown paper packet containing ten cordite
cartridges was fired into with a rifle (.303) loaded with cordite, without
the explosion of a single one of them, which shows its insensibility to
shock.

With respect to the action of cordite upon guns, Sir A. Noble points out
that the erosion caused is of a totally different kind to that of black
powder. The surface of the barrel in the case of cordite appears to be
washed away smoothly by the gases, and not pitted and eaten into as with
black powder. The erosion also extends over a shorter length of surface,
and in small arms it is said to be no greater than in the case of black
powder. Sir A. Noble says in this connection: "It is almost unnecessary to
explain that freedom from rapid erosion is of very high importance in view
of the rapid deterioration of the bores of large guns when fired with
charges developing very high energies. As might perhaps be anticipated
from the higher heat of ballistite, its erosive power is slightly greater
than that of cordite, while the erosive power of cordite is again slightly
greater than that of brown prismatic. Amide powder, on the other hand,
possesses the peculiarity of eroding very much less than any other powder
with which I have experimented, its erosive power being only one-fourth of
that of the other powders enumerated."

TABLE GIVING SOME OF SIR. A. NOBLE'S EXPERIMENTS.
________________________________________________________________________
| |
| VELOCITIES OBTAINED. |
|________________________________________________________________________|
| | | | | |
| | In a 40 | In a 50 | In a 75 | In a 100 |
| | Cal. Gun.| Cal. Gun.| Cal. Gun.| Cal. Gun.|
|____________________________|__________|__________|__________|__________|
| | | | | |
| |Foot Secs.|Foot Secs.|Foot Sees.|Foot Secs.|
| | | | | |
|With cordite 0.4 in. diam. | 2,794 | 2,940 | 3,166 | 3,286 |
| " " 0.3 " | 2,469 | 2,619 | 2,811 | 2,905 |
| " ballistite 0.3 in. cubes| 2,416 | 2,537 | 2,713 | 2,806 |
| " French B.N. for | | | | |
| 6-inch guns | 2,249 | 2,360 | 2,536 | 2,616 |
| " prismatic amide | 2,218 | 2,342 | 2,511 | 2,574 |
| | | | | |
|____________________________|__________|__________|__________|__________|
| |
| ENERGIES REPRESENTED BY ABOVE VELOCITIES. |
|________________________________________________________________________|
| | | | | |
| |Foot Tons.|Foot Tons.|Foot Tons.|Foot Tons.|
| | | | | |
| Cordite 0.4 inch | 5,413 | 5,994 | 6,950 | 7,478 |
| Ballistite 0.3 inch cubes | 4,227 | 4,754 | 5,479 | 5,852 |
| French B.N. | 4,047 | 4,463 | 5,104 | 5,460 |
| Prismatic amide | 3,507 | 3,862 | 4.460 | 4,745 |
|____________________________|__________|__________|__________|__________|

And again, in speaking of his own experiments, he says: "One 4.7-inch gun
has fired 1,219 rounds, and another 953, all with full charges of cordite,
while a 6-inch gun has fired 588 rounds with full charges, of which 355
were cordite. In the whole of these guns, so far as I can judge, the
erosion is certainly not greater than with ordinary powder, and differs
from it remarkably in appearance. With ordinary powder a gun, when much
eroded, is deeply furrowed (these furrows having a great tendency to
develop into cracks), and presents much the appearance in miniature of a
very roughly ploughed field. With cordite, on the contrary, the surface
appears to be pretty smoothly swept away, while the length of the surface
eroded is considerably less."

[Illustration: FIG. 39.--COMPARATIVE PRESSURE CURVES OF CORDITE AND BLACK
POWDER. _a_, Charge, 48 lbs. powder; _b_, charge, 13 lbs. 4 oz. cordite;
_c_, charge, 13 lbs. 4 oz. powder. Weight of projectile, 100 lbs. in
6-inch gun. M.V. Cordite = 1960 feet seconds.]

The pressures given by cordite compared with those given by black powder
in the 6-inch gun will be seen upon reference to Fig. 39, which is taken
from Professor V.B. Lewes's paper, read before the Society of Arts; and
due to Dr W. Anderson, F.R.S., the Director-General of Ordnance Factories.

It has been found that the erosive effect is in direct proportion to the
nitro-glycerine present. The cordite M.D., which contains only 30 per
cent. nitro-glycerine, gives only about half the erosive effect of the old
service cordite. With regard to the heating effect of cordite and cordite
M.D. on a rifle, Mr T.W. Jones made some experiments. He fired fifty
rounds of .303 cartridges in fifteen minutes in the service rifle. Cordite
raised the temperature of the rifle 270 deg. F., and cordite M.D. 160 deg. F.
only.

With regard to the effect of heat upon cordite, there is some difference
of opinion. Dr W. Anderson, F.R.S., says that there is no doubt that the
effect of heat upon cordite is greater than upon black powder. At a
temperature of 110 deg. F. the cordite used in the 4.7-inch gun is
considerably affected as regards pressure.

Colonel Barker, R.A., in reply to a question raised by Colonel Trench,
R.A. (at the Royal Artillery Institution), concerning the shooting
qualities of cordite heated to a temperature of 110 deg. F., said: "Heating
cordite and firing it hot undoubtedly does disturb its shooting qualities,
but as far as we can see, not much more than gunpowder. I fear that we
must always expect abnormal results with heated propellants, either
gunpowder or cordite; and when fired hot, the increase in pressure and
velocities will depend upon the heat above the normal or average
temperature at which firing takes place." Colonel Barker also, in
referring to experiments that had been made in foreign climates, said:
"Climatic trials have been carried out all over the world, and they have
so far proved eminently satisfactory. The Arctic cold of the winter in
Canada, with the temperature below zero, and the tropical sun of India,
have as yet failed to shake the stability of the composition, or
abnormally injure its shooting qualities." Dr Anderson is of opinion that
cordite should not be stored in naval magazines near to the boilers.
Professor Vivian B. Lewes, in his recent Cantor Lectures before the
Society of Arts, suggests that the magazines of warships should be water-
jacketed, and maintained at a temperature that does not rise above 100 deg. F.

~Axite.~--This powder is manufactured by Messrs Kynock Limited, at their
works at Witton, Birmingham. The main constituents of cordite are retained
although the proportions are altered; ingredients are added which impart
properties not possessed by cordite, and the methods of its manufacture
have been modified. The form has also been altered. Axite is made in the
form of a ribbon, the cross section being similar in shape to a double-
headed rail. It is claimed for this powder, that it does not corrode the
barrel in the way cordite does, that with equal pressure it gives greatly
increased velocity, and therefore flatter trajectory. That the effect of
temperature on the pressure and velocity with axite is only half that with
cordite. That the maximum flame temperature of axite is considerably less
than that of cordite, and the erosive effect is therefore considerably
less. That the deposit left in the barrel after firing axite cartridges
reduces the friction between the bullet and the barrel. It is therefore
practicable to use axite cartridges giving higher velocities than can be
employed with cordite, as with such velocities the latter would nickel the
barrel by excessive friction. It is also claimed that the accuracy is
greatly increased. The following results have been obtained with this
same time, and under the same conditions:--

~Axite~ Cartridges with 200-grain bullets.
Velocity 2,726 F.S.
Pressure 20.95 tons.

~Axite~ Cartridges with 215-grain bullets.
Velocity 2,498 F.S.
Pressure 19.24 tons.

~Axite~ Service Cartridges.
Velocity 2,179 F.S.
Pressure 15.76 tons.

~Cordite~ Service Cartridges.
Velocity 2,010 F.S.
Pressure 15.67 tons.

Five rounds from the Service axite and Service cordite were placed in an
oven and heated to a temperature of 110 deg. F. for one hour, and were then
fired for pressure. The following results were obtained:--

~Axite.~ ~Cordite.~
Before heating 15.76 tons per sq. in. 15.67 tons per sq. in.
After " 16.73 " " 17.21 " "
_____ _____

Increase .97 = 6.1% 1.54 = 9.8%

Average Velocities--
Before heating 2,150 F.S. 2,030 F.S.
After " 2,180 " 2,090 "
_____ _____

Increase 30 F.S. = 1-1/2% 60.0 F.S. = 3%

In order to show the accuracy given by axite, seven rounds were fired from
a machine rest at a target fixed at 100 yards from a rifle. Six of the
seven shots could be covered by a penny piece, the other being just
outside. In order to ascertain the relative heat imparted to a rifle by
the explosion of axite and cordite, ten rounds each of axite and cordite
cartridges were fired from a .303 rifle, at intervals of ten seconds, the
temperature of the rifle barrel being taken before and after each series:--

THE RISE IN TEMPERATURE OF THE RIFLE BARREL

With axite was 71 deg. F.
With cordite was 89 deg. F.
Difference in favour of axite 18 deg. F. = 20.2%

The lubricating action of axite is shown by the fact that a series of
cordite cartridges fired from a .303 rifle in the ordinary way, followed
by a second series, the barrel being lubricated between each shot by
firing an axite cartridge alternately with the cordite cartridge. The mean
velocity of the first series of cordite cartridges was 1,974 ft. per
second; the mean velocity of the second series was 2,071 ft. per second;
the increased velocity due to the lubricating effect of axite therefore
was 97 ft. per second. This powder, it is evident, has very many very
excellent qualities, and considerable advantages over cordite. It is
understood that axite is at present under the consideration of the British
Government for use as the Service powder.

~Ballistite.~--Nobel's powder, known as ballistite, originally consisted
of a camphorated blasting gelatine, and was made of 10 parts of camphor in
100 parts of nitro-glycerine, to which 200 parts of benzol were then
added, and 50 parts of nitro-cotton (soluble) were then steeped in this
mixture, which was then heated to evaporate off the benzol, and the
resulting compound afterwards passed between steam-heated rollers, and
formed into sheets, which were then finally cut up into small squares or
other shapes as convenient. The camphor contained in this substance was,
however, found to be a disadvantage, and its use discontinued. The
composition is now 50 per cent. of soluble nitro-cotton and 50 per cent.
of nitro-glycerine. As nitro-glycerine will not dissolve its own weight of
nitro-cotton (even the soluble variety), benzol is used as a solvent, but
is afterwards removed from the finished product, just as the acetone is
removed from cordite. About 1 per cent. of diphenylamine is added for the
purpose of increasing its stability.

The colour of ballistite is a darkish brown. It burns in layers when
ignited, and emits sparks. The size of the cubes into which it is cut is a
0.2-inch cube. Its density is 1.6. It is also, by means of a special
machine, prepared in the form of sheets, after being mixed in a wooden
trough fitted with double zinc plates, and subjected to the heating
process by means of hot-water pipes. It is passed between hot rollers, and
rolled into sheets, which are afterwards put through a cutting machine and
granulated. Sir A. Nobel's experiments[A] with this powder gave the
following results:--The charge used was 5 lbs. 8 oz., the size of the
cubes being 0.2 inch. The mean crusher-gauge pressure was 14.3 tons per
square inch (maximum, 2,210; minimum, 2,142), and average pressure 2,180
atmospheres. The muzzle velocity was 2,140 foot seconds, and the muzzle
energy 1,429 foot tons. A gramme of ballistite generates 615 c.c. of
permanent gases, and gives rise to 1,365 grm. units of heat. Ballistite is
manufactured at Ardeer in Scotland, at Chilworth in Surrey, and also in
Italy, under the name of Filite, which is in the form of cords instead of
cubes. The ballistite made in Germany contained more nitro-cellulose, and
the finished powder was coated with graphite. Its use has been
discontinued as the Service powder in Germany, but it is still the Service
powder in Italy.

[Footnote A: _Proc. Roy. Soc._, vol. lii., p. 315.]

~U.S. Naval Smokeless Powder.~--This powder is manufactured at the U.S.
Naval Torpedo Station for use in guns of all calibres in the U.S. Navy. It
is a nitro-cellulose powder, a mixture of insoluble and soluble nitro-
cellulose together with the nitrates of barium and potassium, and a small
percentage of calcium carbonate. The proportions in the case of the powder
for the 6-inch rapid-fire gun are as follows:--Mixed nitro-cellulose
(soluble and insoluble) 80 parts, barium nitrate 15 parts, potassium
nitrate 4 parts, and calcium carbonate 1 part. The percentage of nitrogen
contained in the insoluble nitro-cellulose must be 13.30+-0.15, and in the
soluble 11.60+-0.15, and the mean nitration strength of the mixture must be
12.75 per cent. of nitrogen. The solvent used in making the powder is a
mixture of ether (sp. gr. 0.720) 2 parts, and alcohol (95 per cent. by
volume) 1 part. The process of manufacture is briefly as follows:[A]--The
soluble and insoluble nitro-cellulose are dried separately at a
temperature from 38 deg. to 41 deg. C., until they do not contain more than 0.1
per cent. of moisture. The calcium carbonate is also finely pulverised and
dried, and is added to the mixed nitro-celluloses after they have been
sifted through a 16-mesh sieve. The nitrates are next weighed out and
dissolved in hot water, and to this solution is added the mixture of
nitro-celluloses and calcium carbonate with constant stirring until the
entire mass becomes a homogeneous paste. This pasty mass is next spread
upon trays and re-dried at a temperature between 38 deg. and 48 deg. C., and when
thoroughly dry it is transferred to the kneading machine. The ether-
alcohol mixture is now added, and the process of kneading begun. It has
been found by experiment that the amount of solvent required to secure
thorough incorporation is about 500 c.c. to each 500 grms. of dried paste.
To prevent loss of solvent due to evaporation, the kneading machine is
made vapour light. The mixing or kneading is continued until the resulting
greyish-yellow paste is absolutely homogeneous so far as can be detected
by the eye, which requires from three to four hours. The paste is next
treated in a preliminary press (known as the block press and is actuated
by hydraulic power), where it is pressed into a cylindrical mass of
uniform density and of such dimensions as to fit it for the final or
powder press. The cylindrical masses from the block press are transferred
to the final press, whence they are forced out of a die under a pressure
of about 500 lbs. per square inch. As it emerges from the final press the
powder is in the form of a ribbon or sheet, the width and thickness of
which is determined by the dimensions of the powder chamber of the gun in
which the powder is to be used. On the inner surface of the die are ribs
extending in the direction of the powder as it emerges from the press, the
object of these ribs being to score the sheets or ribbons in the direction
of their length, so that the powder will yield uniformly to the pressure
of the gases generated in the gun during the combustion of the charge. The
ribbon or sheet is next cut into pieces of a width and length
corresponding to the chamber of the gun for which it is intended, the
general rule being that the thickness of the grain (when perfectly dry)
shall be fifteen one-thousandths (.015) of the calibre of the gun, and the
length equal to the length to fit the powder chamber. Thus, in case of the
6-inch rapid-fire gun the thickness of the grain (or sheet) is 0.09 of an
inch and the length 32 inches. The sheets are next thoroughly dried, first
between sheets of porous blotting-paper under moderate pressure and at a
temperature between 15 deg. C. and 21.5 deg. C. for three days, and then exposed
to free circulation of the air at about 21.5 deg. C. for seven days, and
finally subjected for a week or longer to a temperature not exceeding 38 deg.
C. until they cease to lose weight.

[Footnote A: Lieut. W. Walke, "Lectures on Explosives," p. 330.]

The sheets, when thoroughly dried, are of a uniform yellowish-grey colour,
and of the characteristic colloidal consistency; they possess a perfectly
smooth surface, and are free from internal blisters or cracks. The
temperature of ignition of the finished powder should not be below 172 deg.
C., and when subjected to the heat or stability test, it is required to
resist exposure to a temperature of 71 deg. C. for thirty minutes without
causing discoloration of the test paper.

~W.A. Powder.~--This powder is made by the American Smokeless Powder
Company, and it was proposed for use in the United States Army and Navy.
It is made in several grades according to the ballistic conditions
required. It consists of insoluble gun-cotton and nitro-glycerine,
together with metallic nitrates and an organic substance used as a
deterrent or regulator. The details of its manufacture are very similar to
those of cordite, with the exception that the nitro-glycerine is dissolved
in a portion of the acetone, before it is added to the gun-cotton. The
powder is pressed into solid threads, or tubular cords or cylinders,
according to the calibre of the gun in which the powder is to be used. As
the threads emerge from the press they are received upon a canvas belt,
which passes over steam-heated pipes, and deposited in wire baskets. The
larger cords or cylinders are cut into the proper lengths and exposed upon
trays in the drying-house. The powder for small arms is granulated by
cutting the threads into short cylinders, which are subsequently tumbled,
dusted, and, if not perfectly dry, again placed upon trays in the drying-
house. Before being sent away from the factory, from five to ten lots of
500 lbs. each are mixed in a blending machine, in order to obtain greater
uniformity. The colour of the W.A. powder is very light grey, the grains
are very uniform in size, dry and hard. The powder for larger guns is of a
yellowish colour, almost translucent, and almost as hard as vulcanite. The
powder is said to be unaffected by atmospheric or climatic conditions, to
be stable, and to have given excellent ballistic results; it is not
sensitive to the impact of bullets, and when ignited burns quietly, unless
strongly confined.

Turning now to the smokeless powders, in which the chief ingredient is
nitro-cellulose in some form (either gun-cotton or nitro-lignine, &c.),
one of the first of these was Prentice's gun-cotton, which consisted of
nitrated paper 15 parts, mixed with 85 parts of unconverted cellulose. It
was rolled into a cylinder. Another was Punshon's gun-cotton powder, which
consisted of gun-cotton soaked in a solution of sugar, and then mixed with
a nitrate, such as sodium or potassium nitrate. Barium nitrate was
afterwards used, and the material was granulated, and consisted of
nitrated gun-cotton.

The explosive known as tonite, made at Faversham, was at first intended
for use as a gunpowder, but is now only used for blasting.

~The Schultze Powder.~--One of the earliest of the successful powders
introduced into this country was Schultze's powder, the invention of
Colonel Schultze, of the Prussian Artillery, and is now manufactured by
the Schultze Gunpowder Company Limited, of London. The composition of this
powder, as given in the "Dictionary of Explosives" by the late Colonel
Cundall, is as follows:--

Soluble nitro-lignine 14.83 per cent.
Insoluble " 23.36 "
Lignine (unconverted) 13.14 "
Nitrates of K and Ba 32.35 "
Paraffin 3.65 "
Matters soluble in alcohol 0.11 "
Moisture 2.56 "

This powder was the first to solve the difficulty of making a smokeless,
or nearly smokeless powder which could be used with safety and success in
small arms. Previously, gun-cotton had been tried in various forms, and in
nearly every instance disaster to the weapon had followed, owing to the
difficulty of taming the combustion to a safe degree. But about 1866
Colonel Schultze produced, as the result of experiments, a nitrated wood
fibre which gave great promise of being more pliable and more easily
regulated in its burning than gun-cotton, and this was at once introduced
into England, and the Schultze Gunpowder Company Limited was formed to
commence its manufacture, which it did in the year 1868. During the years
from its first appearance, Schultze gunpowder has passed through various
modifications. It was first made in a small cubical grain formed by
cutting the actual fibre of timber transversely, and then breaking this
veneer into cubes. Later on improvements were introduced, and the wood
fibre so produced was crushed to a fine degree, and then reformed into
small irregular grains. Again, an advance was made in the form of the wood
fibre used, the fibre being broken down by the action of chemicals under
high temperature, and so producing an extremely pure form of woody fibre.
The next improvement was to render the grains of the powder practically
waterproof and less affected by the atmospheric influences of moisture and
dryness, and the last improvement to the process was that of hardening the
grains by means of a solvent of nitro-lignine, so as to do away with the
dust that was often formed from the rubbing of the grains during transit.

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23