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PRINCIPLES OF
FIRING.
653. TARGET practice will enable Soldiers to learn the use of
their fire-arms, in the course of time; but, if they fully
understand the principles of firing, their practice will be
materially aided. The following is taken from the "Instructions
for Field Artillery," and is as applicable to small arms as to
cannon.
POINTING AND RANGES."
"To point a piece is
to place it in such a position that the shot may reach the object it
is intended to strike. To do this, the axis of the trunnions being
horizontal, the line of metal, called also the natural line of
sight, must be so.directed as to pass through the object, and then
the elevation given to the piece to throw the shot the required
distance. The direction
is given from the
trail, and the elevation from the breech; the trail being traversed
by a handspike, and the breech raised or depressed by an elevating
screw.
"The axis of
the piece coincides
with that of the cylinder of the bore.
"The line of
sight in pointing
is the line of direction from the eye to the object. It lies in a
vertical plane, passing through, or parallel to, the axis of the
piece.
"The angle
of sight is the
angle which the line of sight makes with the axis of the piece.
"The natural
tine of sight is
the straight line passing through the highest points of the base
ring, and the swell of the muzzle, muzzle sight, or muzzle band.
"The natural
angle of sight is
the angle which the natural line of sight makes with the axis of the
piece.
"The disport
of a piece is half
the difference between the diameters of the base ring and swell of
the muzzle, or the muzzle band. It is therefore the tangent of the
natural angle of sight, to a radius equal to the distance from the
highest point of the swell of the muzzle or muzzle band, to the
plane passing through the rear of the base ring .
"By range is
commonly meant the distance between the piece and the object which
the ball is intended to strike; or, the first graze of the ball upon
the horizontal plane on which the carriage stands. Point-blank
range is the
distance between the piece and the point-blank. Extreme
range is the
distance between the piece and the spot where the ball finally
rests.
"Theory of pointing—The point-blank is
the second point of intersection of the trajectory, or curve
described by the projectile in its flight with the line of sight. As
the angle of sight is increased, the projectile is thrown farther
above the line of sight, and the trajectory and point blank distance
become more extended.
"The point-blank range increases with the velocity,
the diameter,
and the density
of the ball. It is
also affected by the inclination of the line of sight; but with the
angles of elevation used in field service, this effect is too small
to be taken into account.
"A piece is said to be aimed point-blank
when the line of
metal, which is the natural line of sight, is directed upon the
object. This most be the case when the object is at point-blank
distance. When at a greater distance, the pendulum-hausse, or the
tangent scale, is raised upon the breech until the sight is at the
height which the degree of elevation for the distance may require.
An artificial line of sight and an artificial
point-blank, are
thus obtained, and the piece is aimed as before.
"The different lines, angles, &c. which an artilleryman
has to take into account in pointing, will be best understood by the
following figure:
"A B is the axis of the piece. B I F L is the trajectory, or
curve described by the projectile in its flight. C D F is the
natural line of sight. C D A is the natural angle of sight.
"The projectile, thrown in the direction of the axis A B fi
G, is acted upon by the force of gravity, and begins to fall at once
below the line at the rate of 16 1/2
feet for one
second, 64 1/3 for two, 144 3/4 for three, and so on in proportion
to the time. It cuts the line of sight at B, a short distance from
the muzzle of the piece and descending, again cuts it at the point
F. This second point of intersection is the point-blank.
"Pendulum-hausse—The instrument
at present in most general use in pointing field-guns at objects
beyond the natural point-blank, is called a pendutum-hausse,
of which the
component parts are denominated the scale,
the slider,
and the seat.
The scale
is made of
sheet-brass: at the lower end is a brass bulb filled with lead. The slider
is of thin brass,
and is retained in any desired position on the scale by means of a
brass set screw with a milled head. The scale is passed through a
silt in a piece of steel, with which it is connected by a brass
screw, forming a pivot on which the scale can vibrate laterally:
this slit is made long enough to allow the scale to take a vertical
position in any ordinary
cases of inequality
of the ground on which the wheels of the carriage may stand. The
ends of this piece of steel form two journals, by means of which the
scale is supported on the seat
attached to the
piece, and is at liberty to vibrate in the direction of the axis of
the piece. The seat is
of iron, and is fastened to the base of the breech by three screws,
in such manner that the centres of the two journal notches shall be
at a distance from the axis equal to the radius of the base ring.
"A muzzle
sight of iron is
screwed into the swell of the muzzle of guns,
or into the middle
of the muzzle ring of howitzers.
The height of this
sight is equal to the dispart
of the piece, so
that a line from the top of the muzzle sight to the pivot
of the scale is
parallel to the axis of the piece. Consequently the vertical plane
of sight passing through the centre line of the scale and the top of
the muzzle sight will be also parallel to the axis in any position
of the piece: the scale will therefore always indicate correctly the
angle which the line of sight makes with the axis. The seat
for suspending the
hausse upon the piece is adapted to each piece according to the
varying inclination of the base of the breech to the axis. The hausse,
the seat,
and the muzzle
sight, varying as
they do, in their construction and arrangement, according to the
configuration of the piece upon which they are intended to be used,
are marked for the kind of piece to which they belong. The
graduations on the scale are the tangents of each quarter of a
degree, to a radius equal to the distance between the muzzle sight
and the centre of the journal-notches, which are, in all cases, one
inch in rear of the base ring.
"The hausse, when not in use, is carried by the gunner in a
leather pouch, suspended from a shoulder-strap.
"PRACTICAL HINTS ON POINTING.
"As it is impossible to point a piece correctly without
knowing the distance
of the object,
artillerymen should be frequently practiced in estimating distances
by the eye alone, and verifying the estimate afterwards, either by
pacing the distance, or by actual measurement with a tape-line or
chain, until they acquire the habit of estimating them correctly.
"Shells are
intended to burst in
the object aimed
at: spherical case
shot are intended
to burst from fifty to seventy-five yards short of it.
"Shell or spherical case firing, for long ranges, is less
accurate than that of solid shot.
"At high elevations a solid shot will range farther than a
shell or spherical case shot of the same diameter fired with an
equal charge. But at low elevations, the shell or spherical case
will have a greater initial velocity, and a longer range. If,
however, the charges be proportioned to the weights of the
projectiles, the solid shot will in all cases have the longest
range.
"The velocity or range of a shot is not affected in any
appreciable degree by checking the recoil of the carriage, by using
a tight wad, or by different degrees of ramming.
"The principal causes which disturb the true flight of the
projectile may be simply stated as follows:
"tat. If the wheels of the carriage are not upon the same
horizontal plane, the projectile will deviate towards the lowest
side of the
carriage.
"2d. If the direction of the wind is across the line of
fire, deviations in the flight of the projectile will be occasioned
and in proportion to the strength of the wind, the angle its
direction makes with the line of fire, and the velocity of the
projectile.
"3d. If the centre of gravity of the projectile be not
coincident with the centre of figure, the projectile will deviate
towards the heaviest
side, that is, in
the same direction that the centre of gravity of the projectile,
while resting in the piece, lies with regard to the centre of
figure. Therefore, if a shot be placed in the piece so that its
centre of gravity is to the right
of the centre of
the ball, the shot will deviate towards the right;
and vice versa. If
the centre of gravity be above the centre of figure, the range will
be increased; if
below, it
will be diminished.
"Should an enemy’s cavalry be at a distance of 1000 yards
from the battery it is about to charge, it will move over the first
400 yards at a walk, approaching to a gentle trot, in about four and
a half minutes; it passes over the next 400 yards at a round trot,
in a little more than two minutes; and over the last 200 yards at a
gallop, in about half a minute, the passage over the whole distance
requiring about seven minutes. This estimate will generally be very
near the truth, as the ground is not always even, nor easy to move
over Many losses arise from the fire of the artillery and from
accidents, and the forming and filling up of intervals create
disorder; all of which contribute to retard the charge. Now, a piece
can throw, with sufficient deliberation for pointing, two solid shot
or three canisters per minute, Each piece of the battery, therefore,
might fire nine rounds of solid shot upon the cavalry whilst it is
passing over the first 400 yards; two rounds of solid shot and three
of canister whilst it is passing over the next 400 yards; and two
rounds of canister whilst it is passing over the last 200 yards—making
a total from each gun of eleven round shot and five canis ters. To
this is added the fire of the supporting infantry.
"Care should be taken not to cease firing solid shot too
soon, in order to commence with canister If the effect of the latter
be very great on hard, horizontal, or smooth ground, which is
without obstruction of any kind, it is less on irregular and soft
ground, or on that covered with brushwood; for, if the ground be not
favorable, a large portion of the canister shot is intercepted. A
solid shot is true to its direction, and, in ricochet, may hit the
second line if it misses the first.
"Solid shot should be used from 350 yards upwards: the use
of canister should begin at 350 yards, and the rapidity of the fire
increase as the range diminishes. In emergencies, double charges of
canister may be used at 150 or 160 yards, with a single cartridge.
"Spherical case ought not, as a general rule, to be used for
a less range than 500 yards; and neither spherical case nor shells
should be fired at rapidly advancing bodies, as, for instance,
cavalry charging.
"The fire of spherical case and of shells on bodies of
cavalry in line or column, and in position, is often very effective.
To the destructive effects of the projectiles are added the
confusion and disorder occasioned amongst the horses by the noise of
their explosion; but neither shells nor spherical case should be
fired so rapidly as solid shot.
"In case of necessity, solid shot may be fired from
howitzers.’
654. In the use of small anus, greater accuracy is necessary in
the estimation of distances; and no one can fire accurately without
knowing the correct distance. Soldiers should practice estimating
distances. The stadium, represented in "Target Practice,"
is an instrument intended to measure distances. Every soldier can
readily make his own stadium, that will answer the purpose, by using
a small stick of hard wood, or bone, or even his screw-driver, and
graduating it for the purpose. The following diagram will explain
the principle:
655. A is the eye, B is the hand extended to the full length of
the arm, and holding the instrument to be graduated, C is a man of
medium height.
Place the man first at fifty yards, and measure his height on the
stick B, and mark it; then place him at one hundred yards, and
another mark will be obtained: and so on for the principal
distances. Each new position will give a new mark on the scale, and
the height of the man will measure smaller every time he is removed
farther away. The arm must always be extended to the full length,
and the stick must always be used to measure the height of a man, or
some object known to be about the same height.
656. In estimating distances by the difference in appearance of
the same object at different distances, no fixed rules can be laid
down, as the eyesight differs materially in different persons. The
only way is for each individual to fix his own rules by closely
observing the appearance of the same object at known distances.
Thus, at one distance, he is able to recognize a man’s face and
all the details of his dress; a little farther, and he is only able
to recognize certain prominent features; still farther, he will be
able to distinguish a human figure, but is unable to say whether it
is male or female. Practice will soon enable one to judge very
correctly, by the various changes in the appearance of the human
form, how far it is away.
657. The color of the objects, the condition of the atmosphere,
and the formation of the ground affect the estimate of distances
very materially. Bright, positive colors seem closer, and neutral
colors more distant; green fields will, therefore, appear closer
than ploughed fields. In clear weather, with the sun behind the
viewer, objects appear nearer than in dark, cloudy weather, at
twilight, by the light of the moon, or dusty or foggy weather. Where
the ground is broken, the objects appear larger than on a level
plain, and large objects of one color seem to diminish the distance.
658. Tall objects seem closer than lower ones looking down,
objects seem shorter than when
looking up. A good eye of ordinary capacity will distinguish the
shingles on a house at two hundred and fifty to three hundred yards,
in clear weather.
At six hundred to eight hundred yards, the crossbars of the
windows are still visible.
At twelve hundred to fifteen hundred yards, single beams,
individual trees, guide-posts, &c. are still seen.
At two thousand five hundred to three thousand yards, large trees
are still visible.
At four thousand to five thousand yards, the chimneys are still
in sight on the housetops.
At two to three miles, ordinary dwelling-houses are recognized;
and churches and windmills are recognizable from six to nine miles.
659. At two thousand yards, a line of infantry looks like a black
line, with a bright line over it; cavalry seems a thicker line, with
the upper edge broken or notched. The movements can be recognized.
At twelve hundred to fifteen hundred yards, cavalry can be
distinguished readily from infantry; the ranks of the latter are
visible at twelve hundreds yards.
At one thousand yards, the line of the heads and the motions of
the legs of men of the infantry are visible, and the horses’ heads
of cavalry can be distinguished.
At eight hundred yards, the upper outline of the men are visible
of infantry, and, if cavalry, you can distinguish the motions of the
horses’ legs.
At six hundred yards, men and horses are distinctly visible, but
colors are not distinguishable, except white; the kind of head-dress
can be recognized.
At four hundred yards, the ornaments are visible on the
head-dress, and colors are distinguishable.
At two hundred yards, the men’s heads are distinctly visible.
At one hundred and fifty to two hundred yards, you can see the
line of the men’s eyes.
At eighty yards, the men’s eyes are distinct points.
At twenty-five to thirty yards, you can see the white of the eye.
660. Sound travels at the rate of one thousand and eighty-five
feet per second, and the difference of time between the flash and
the report of a gun will give the distance. On a still night, troops
moving at a route step can be heard from five to six hundred yards;
when keeping step, from seven hundred and fifty to eight hundred
yards. A troop of horse, at a walk, seven hundred to eight hundred
yards; at a gallop or trot, one thousand yards. In stormy weather,
the human voice cannot be heard over eighty yards.
661. In firing, men should drop the muzzle of the musket below
the object and obtain the correct sight by raising it again. Men are
very liable to overshoot firing down hill, and are much more liable
to hit firing up hill. Where the hill is steeper than forty-five
degrees, men will overshoot, even if they aim at the feet, if the
distance is one hundred yards or more.
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