certain flanges or projections to fit into the grooves of the gun in
loading. These are usually deep and few in number, rounded at their
bottom edges so as to cause the flanges or studs to pass up the
inclined side when rotation is imparted. This is the system at present
adopted in England. Though this plan affords a certain means of
communicating the rifle motion, it has not always been found a safe one,
probably from the wedging of the flanges in the grooves. Besides, the
dirt from the burning of the powder collects in the grooves; and as it
is difficult to clean them by the usual means, the projectile is liable
to meet with obstruction in loading. To obviate these difficulties, the
flanges are sometimes made of softer metal than the body of the
projectile. Guns for flanged or studded projectiles usually have from 3
to 9 grooves, 0.15 to 0.25 inch deep.
2. _The Compressive System._--By this system the projectile is forced by
the action of the powder through the bore of a piece whose diameter
without the grooves is less than the diameter of the projectile. Such
are the projectiles for the breech-loading Krupp and Broadwell guns.
These usually consist of cast iron or steel, and are covered with a
coating of lead or other soft metal having horizontal ribs or
corrugations, which is secured by a chemical solder, or cast into
undercuts in the body of the shot. As the projectile is forced through
the bore, an impression of the rifling is cut out of the ribs, the lead
thus displaced finding room in the grooves between. This system has been
found to work satisfactorily in breech-loading guns. The rifling should
be shallow and consist of numerous grooves, slightly narrowing towards
the muzzle. Large guns usually have from 20 to 76, from .05 to .08 inch
deep. Experiments are now being made, with prospects of success, to
substitute bands of soft copper encircling the projectile for the lead
coating.
3. _The Expansive System._--This system has been so exclusively used in
the United States that it has frequently been called the American
system. It embraces all projectiles which are loaded without regard to
the rifling, but which are fitted with an expanding portion of some
softer metal, as pewter, copper, wrought iron, or _papier-maché_, which
is forced into the grooves by the discharge. This system requires for
its rifling fewer grooves than the compressive, but a somewhat greater
number than the flanged system. Among the projectiles of this class used
during the civil war were the Blakely, Dyer, Hotchkiss, James, Parrott,
Reed, Schenkle, and Stafford. The principal objections to an expanding
or compound projectile are its want of strength to resist a charge of
powder proportionately as large as that employed for a simple
projectile, and the danger of its breaking and wedging in the bore of
the piece. Of late years, however, marked improvements have been made,
and projectiles of this class can now be safely fired with double their
former charges. The large projectiles of this description now used in
the United States consist of the usual cast-iron body having a sabot,
or ring of brass or copper either cast or screwed to its base. This ring
is divided into an upper and lower flange or lip by an annular groove.
When the gun is fired, the gases enter this groove, forcing the lower
flange down upon the projectile and the upper or outer into the rifling
of the gun, where it is kept during its passage through the bore.
_Armstrong Projectile._--But one kind of projectile is used in the
Armstrong breech-loading guns for the field service, and this is so
constructed as to act as a shot, shell, or case-shot at pleasure. It
consists of a very thin cast-iron shell, inclosing 42 segment-shaped
pieces of cast iron built up so as to form a cylindrical cavity in the
centre, which contains the bursting charge and the concussion-fuze. The
exterior of the shell is thinly coated with lead, which is applied by
placing the shell in a mold and pouring it in a melted state. The lead
is also allowed to percolate among the segments, so as to fill up the
interstices, the central cavity being kept open by the insertion of a
steel core. In this state the projectile is so compact that it may be
fired without injury, while its resistance to a bursting charge is so
small that less than one ounce of powder is required to burst it. When
the projectile is to be tired as a shot, it requires no preparation; but
the expediency of using it otherwise than as a shell is doubted. To make
it available as a shell, the bursting tube, the concussion- and
time-fuzes, are all to be inserted; the bursting tube entering first and
the time-fuze being screwed in at the apex. If the time-fuze be
correctly adjusted, the shell will burst when it reaches within a few
yards of the object; or failing in this, it will burst by the
concussion-fuze when it strikes the object, or grazes the ground near
it. If it be required to act as a canister-shot upon an enemy close to
the gun, the regulation of the time-fuze must be turned to the zero of
the scale, and then the shell will burst on leaving the gun. The
Armstrong projectiles for the muzzle-loading guns have rows of brass or
copper studs projecting from their sides to tit into the grooves of the
gun, which are constructed on the _shunt_ principle. The projectile is
made of wrought iron, or low steel, with very thick sides. There is no
fuze, the explosion resulting from the heat generated by the impact, and
the crushing in of the thin cap which closes the mouth of the
powder-chamber. The sides and bottom of the shell being thick enough to
resist crushing by the impact, and also to resist the explosive force of
the bursting charge, its effect will, after penetration, be expended on
the backing of the armor, or the decks which the armor is intended to
screen. Such projectiles are called “blind shells.”
_Blakely Projectile._--Capt. Blakely’s projectile has an expanding cap
attached to its base by means of a single tap-bolt in the centre. It is
prevented from turning by radial grooves cast on the surface of the
bottom of the projectile, into which the cup is pressed by the charge.
The angle between the curved sides of the cup and the bottom of the
projectile is filled with a lubricating material. On the forward part of
the body are soft metal studs, more numerous than the grooves of the
bore of the piece, that some of them may always form a bearing surface
for the projectile against the lands. The driving sides of the grooves
are deeper than the others.
_Dyer Projectile._--The Dyer projectile is composed of a cast-iron body,
and a soft metal expanding cup, attached to its base. The adhesion of
the cup is effected by tinning the bottom of the projectile, and then
casting the cup on to it. The cup is composed of an alloy of lead, tin,
and copper, in certain proportions. This projectile, as improved by Mr.
Taylor at the Washington Arsenal, gives good results for even as large a
caliber as 12 inches.
_French Projectile._--The projectile used in the French field service is
made of cast iron, and has 12 zinc studs on its sides, arranged in
pairs, so as to fit the 6 grooves of the gun. For the larger cannon
projectiles, but 3 studs are used, and these are cast on the projectile,
nearly opposite to its centre of gravity; the bearing sides of the studs
are faced with white metal to diminish friction against the grooves of
the bore. The shape of the grooves is such as to centre the projectile.
The latter projectile is used with increasing, the former with grooves
of uniform twist. Russian, Austrian, and Spanish artillery projectiles
belong to the studded, or button class, but differ from each other in
the details of their construction.
_Hotchkiss Projectile._--The Hotchkiss projectile is composed of three
parts: the body, the expanding ring of lead, and the cast-iron cup. The
action of the charge is to crowd the cup against the soft metal ring,
thereby expanding it into the rifling of the gun. The time-fuze
projectile has deep longitudinal grooves cut on its sides to allow the
flame to pass over and ignite the fuze. The last rifle projectile
submitted by Mr. Hotchkiss has an expanding cup of brass attached to its
base in a peculiar manner. The cup is divided into four parts by thin
projections on the base of the projectile. This arrangement is intended
to facilitate the expansion of the cup and to allow the flame to pass
over to ignite the fuze.
_James Projectile._--The expanding part of the James projectile consists
of a hollow formed in the base of the projectile, and eight radial
openings, which extend from this hollow to the surface for the passage
of the flame of the charge, which presses against and expands into the
grooves of the bore, an envelope or patch, composed of paper, canvas,
and lead. In a later pattern of this projectile, the internal cavity and
radial openings are omitted, and the outside is furrowed with
longitudinal grooves which increase in depth towards the base of the
projectile, forming inclined planes, up which the outer covering of lead
and canvas is moved by the force of the charge and expanded into the
rifling of the piece.
The first projectile used in Parrott guns was invented by Dr. Reed of
Alabama, in 1856 or 1857, and was made at Parrott’s foundry. It
consisted of a soft wrought-iron cup, slightly swedged to fit the
grooves, upon which was cast the body of the shot.
_Palliser Projectile._--This is the most formidable armor-piercing
projectile in use. It owes its efficiency to the material used,--chilled
cast iron. In the later forms the head only is chilled, the body being
cast in sand. Both shot and shell are cast with a core. The shell is
“blind.” The curve of the ogival head is struck with a radius of one and
one-half times the diameter of the projectile.
_Parrott Projectile._--Capt. Parrott’s projectile, as now made, is
composed of a cast-iron body with a brass ring cast into a rabbet formed
around its base. The flame presses against the bottom of the ring and
underneath it so as to expand it into the grooves of the gun. To prevent
the ring from turning in the rabbet, the latter is recessed at several
points of its circumference. _Parrott’s incendiary shell_ has two
compartments formed by a partition at right angles to its length. The
lower and larger space is filled with a burning composition, the upper
one is filled with a bursting charge of powder, which is fired by a
time- or concussion-fuze. The burning composition is introduced through
a hole in the bottom of the shell, which is stopped up with a
screw-plug.
_Sawyer Projectile._--The Sawyer projectile has upon its sides six
rectangular flanges or ribs to fit into corresponding grooves of the
bore. To soften the contact with the surface of the bore, the entire
surface of the projectile is covered with a coating of lead and
brass-foil. The soft metal at the corner of the base is made thicker
than at the sides to admit of being expanded into the grooves, and
thereby closing the windage. In the latest pattern of Sawyer
projectiles, the flanges are omitted, and the projectiles are made to
take the grooves by the expansion of the soft metal at the base, which
is peculiarly shaped for this purpose.
_Schenkle Projectile._--Schenkle’s projectile is composed of a cast-iron
body, the posterior portion of which is a cone. The expanding portion is
a _papier-maché_ sabot or ring, which is expanded into the rifling of
the bore by being forced on to the cone by the action of the charge. On
issuing from the bore the wad is blown to pieces, leaving the projectile
unencumbered in its flight. A great difficulty has been found in
practice in always getting a proper quality of material for the sabot,
and in consequence, these projectiles have not been found to be
reliable.
_Scott Projectile._--The shell devised by Commander Scott of the British
navy, for firing molten iron, has three ribs cast upon it, which fit
grooves so constructed as to centre it in the bore of the gun when
fired. The interior of this shell is lined with loam to prevent the heat
of the charge from penetrating through to the bursting charge. It is
supposed to be broken and its contents diffused on striking the object.
_Whitworth Projectile._--The cross-section of the bore of the Whitworth
gun is a hexagon with the corners slightly rounded. The projectile is
first formed so that its cross-section is a circle, and its sides taper
towards both ends. The middle portion is then carefully planed off to
fit the bore of the gun. The Whitworth blind shell for firing against
armor-plates, is made of tempered steel, and each end is closed with a
screw. To prevent the heat of impact from acting too soon on the
bursting charge, it is surrounded by one or more thicknesses of flannel.
A 7-inch shell of this kind has been found to have sufficient strength
and stiffness to penetrate 5 inches of wrought iron before bursting.
_Confederate Projectiles._--The rifle projectiles used by the
Confederates in the late war belonged, with a few exceptions, to the
expanding class. Besides the above there are three kinds of projectiles
much used in the U. S. service, viz.:
_Absterdam Projectile._--The best form is cast in a single piece, and
has an expanding ring of brass which projects three-eighths of an inch
beyond the base of the projectile.
_Eureka Projectile._--Consists of a cast-iron body in one piece, with a
brass sabot; the sabot is an annular disk intended to move on the
frustum of a cone with an expanding cup in rear to take the grooves.
_Ordnance Projectile._--Consists of a cast-iron body, with a sabot
composed of an alloy of lead and tin, which is cast on the base of the
projectile, and is held in position by undercuts and dovetails, the
action of the charge being to force the sabot on the cast-iron body and
to make it take the grooves.
Projectiles of special construction were formerly much used for
particular purposes, as:
_Bar-shot_, which consisted of two hemispheres or spheres connected by a
bar of iron either rigidly or in such a manner as to traverse its
length; these were useful in cutting the masts and rigging of ships.
_Chain-shot._--This differed from bar-shot only in the mode of
connection, which was a chain instead of a bar.
_Chain-ball._--To arrest the motion of rotation of an oblong projectile
thrown under high angles, and with a moderate velocity, it has been
proposed to attach a light body to its posterior portion by means of a
cord, or chain, which will offer a resistance to the flight of the
projectile, and cause it to move with its point foremost.
_Nail-ball._--A round projectile, having a projecting pin to prevent it
from turning in the bore of the piece.
_Grooved Ball._--An oblong projectile, having spiral grooves cut along
its base, by means of which the action of the charge produces rotation
about the longer axis of the projectile. Sometimes these grooves are cut
in the forward part of the projectile for the action of the air. Neither
of these plans has succeeded in practice.
_Bullets._--A bullet is a leaden projectile discharged from a musket,
fowling-piece, pistol, or similar weapon.
_Spherical Bullets._--When smooth-bore muskets alone were used the
bullets were chiefly spherical in form and made by casting; at present,
however, spherical bullets are manufactured by a compressing machine
invented by Mr. George Napier. They are denominated by the number
contained in a pound. In consequence of the great improvements that have
been made of late in small-arms, the spherical bullet is now very little
employed for military purposes, its use being chiefly confined to
case-shot.
_Oblong Bullets._--Are denominated by their diameter and weight. About
1600, when rifles began to be used as a military weapon, spherical
bullets were fired; in the early part of the 18th century, however, it
was found that good results could be obtained by the use of oblong
projectiles of elliptical form. The great difficulty, however, of
loading the rifle, which was ordinarily accomplished by the blows of a
mallet on a stout iron ramrod, prevented it from being generally used in
regular warfare. The foregoing plan was afterwards improved by making
the projectile a little smaller than the bore, and wrapping it with a
patch of cloth greased to diminish the friction in loading. The
improvements which have been made in the last thirty years have entirely
overcome this difficulty, and rifles are now almost universally
employed, although until 1855 the mass of the American infantry was
armed with smooth-bored muskets. The first person to overcome the
difficulty of loading rifles was M. Delavigne, an officer of the French
infantry. His plan, proposed in 1827, was to make the projectile small
enough to enter the bore easily and to attach it to a sabot, which, when
in position, rested upon the shoulder of a cylindrical chamber formed at
the bottom of the bore to contain the powder. In this position the
projectile was struck two or three times with the ramrod, which expanded
the lead into the grooves of the barrel. The method of Delavigne was
afterwards improved by Thouvenin and Minié, both officers of the French
service. The projectiles suggested by them were elongated in form and
the metal of the projectile was forced into the grooves of the rifling
by means of a plug or cup driven into the base of the projectile, which
was cast hollow for that purpose. The cup used in the Minié bullet wits
made of sheet-iron. Mr. Greener of England appears to have been the
first person to utilize this expanding or dilating action. Various other
bullets have been invented, of greater or less usefulness, as the
Whitworth, Pritchett or Enfield, and those used in the French, Austrian,
and Swiss services. In the British service, the Enfield bullet is
employed; this has a perfectly smooth exterior, and a conical boxwood
plug inserted into a cavity at the base; they are made by machinery
which draws in a coil of leaden rod, unwinds it, cuts it to the required
length, stamps out the bullets with steel dies, drops them into boxes,
and conveys them away.
_United States Bullets._--The bullets used in the U. S. service are of
two kinds, one for the rifle and carbine ball-cartridge weighing 405
grains, the other for the revolver cartridge weighing 230 grains. The
metal used is an alloy of 16 parts of lead and 1 part of tin. The bullet
in shape is a cylinder surmounted by a conical frustum terminating in a
spherical segment. It has three rectangular cannelures which contain the
lubricant. This latter is protected by the case which covers more than
half the length of the bullet. A dished cavity is made in the base of
the bullet to bring it to the proper weight.
=Projectiles, Theory of.= Is the investigation of the path, or
_trajectory_ as it is called, of a body which is projected into space. A
body thus projected is acted upon by two forces, the _force of
projection_, which, if acting alone, would carry the body onwards
forever in the same direction and at the same rate; and the _force of
gravity_, which tends to draw the body downwards towards the earth. The
force of projection acts only at the commencement of the body’s motion;
the force of gravity, on the contrary, continues to act effectively
during the whole time of the body’s motion, drawing it farther and
farther from its original direction, and causing it to describe a curved
path, which, if the body moved in a vacuum, would be accurately a
parabola.
_Trajectory in Vacuo._--This general theory is not the object of the
present discussion, but simply the theory of projectiles as far as it
relates to fire-arms. The path that the centre of gravity of a
projectile would describe in _vacuo_ would be a parabola, and the
greatest range given by an angle of fire of 45°. Under the same angles
of fire the range would be proportional to the squares of the
velocities, the velocity least at the summit of the trajectory, and the
velocities at the two points in which the trajectory cuts the horizontal
plane equal. The time of flight would be given for an angle of 45° by
the formula:
_T_ = ¹⁄₄√_X_
In which _T_ represents the time of flight, and _X_ the range expressed
in feet. These results are found to answer in practice for projectiles
which experience slight resistance from the air, or for heavy
projectiles moving with low velocities, as is usually the case with
those of mortars and howitzers, for which, within certain limits, the
above results are sufficiently accurate in practice.
_Trajectory in Air._--A body moving in air experiences a resistance
which diminishes the velocity with which it is animated. Thus it has
been shown that certain cannon-balls do not range one-eighth as far in
the air, as they would if they did not meet with this resistance to
their motion, and small-arm projectiles which have but little mass are
still more affected by it. This resistance is expressed by the formula:
( _v_)
_P_ = _A_{p}R_²(1 + ---)_v_²;
( _r_)
in which _P_ represents the resistance in the terms of the unit of
weight, _v_ the velocity, and _pR_² the area of a cross-section of the
projectile, _A_ the resistance in pounds on a square foot of the
cross-section of a projectile moving with a velocity of one foot, _r_ is
a linear quantity depending on the velocity of the projectile. For all
service spherical projectiles _A_ is .000514, and for all service
velocities _r_ is 1.427 feet; the value of _A_ for the rifle-musket
bullet is .000358; hence, the resistance of the air is about one-third
less on the ogival than on the spherical form of projectile. _A_ being a
function of the density of air, its value depends on the temperature,
pressure, and hygrometric condition. It has been demonstrated that the
final velocity of a projectile falling in the air is directly
proportional to the product of its diameter and density, and inversely
proportional to the density of the air; the retarding effect of the air
is less on the larger and denser projectiles, and for the same caliber
an oblong projectile will be less retarded by the air than one of
spherical form and consequently with an equal, perhaps less, initial
velocity, its range will be greater. It has also been shown that great
advantage in point of range is obtained by using large projectiles
instead of small ones, solid projectiles instead of hollow ones, leaden
projectiles instead of iron ones, and oblong projectiles instead of
round ones. The ogival form, or the form of the present rifle-musket
bullet, experiences less resistance in passing through the air than any
other known. In consequence of the variable nature of the resistance of
the air, it has been found impossible to find an accurate expression for
the trajectory. Capt. Didion, of Metz, has, however, found an
approximate solution; he states that all cases of the movement of a
projectile may be divided into three classes: 1st. When the angle of
projection is slight or does not exceed 3°, as in the ordinary fire of
guns, howitzers, and small-arms,--for slight variations of the angle of
projection above or below the horizontal, the form of the trajectory may
be considered constant, and when the object is but slightly raised above
or depressed below the horizontal plane, it may be considered as in
this plane. 2d. When angles of projection do not exceed 10° or 15°, as
in the ricochet fire of guns, howitzers, and mortars. 3d. When the angle
of projection exceeds 15°, as is the case in mortar fire. For each of
these cases he has deduced formulæ, by means of which the range, time of
flight, etc., can be determined. As a projectile rises in the ascending
branch of its trajectory, its velocity is diminished by the retarding
effect of the air, and the force of gravity, in consequence of the
resistance of the air alone, the velocity continues to diminish to a
point a little beyond the summit of the trajectory, where it is a
minimum, and from this point it increases, as it descends, under the
influence of the force of gravity, until it becomes uniform, which event
depends on the diameter and weight of the projectile, and the density of
the air.