AN IMPROVED METHOD OF GIVING ROTATION AND CENTRATION TO PROJECTILES, AND FOR CHECKING THE ESCAPE OF POWDER GAS
Year: 1877

page_text: LETTERS PATENT to Thorsten Wilhelm Nordenfelt, of 1, Saint Swithin's Lane,
London, E.C., Civil Engineer, for the Invention of "AN IMPROVED METHOD
OF GIVING ROTATION AND CENTRATION TO PROJECTILES, AND FOR CHECKING
THE ESCAPE OF POWDER GAS."
Sealed the 29th April 1878, and dated the 3rd November 1877.
PROVISIONAL SPECIFICATION left by the said Thorsten Wilhelm Nordenfelt
at the Office of the Commissioners of Patents on the 3rd November 1877.
THORSTEN WILHELM NORDENFELT, of 1, Saint Swithin's Lane, London, E.C.,
Civil Engineer. "AN IMPROVED METHOD OF GIVING ROTATION AND CENTRATION
TO PROJECTILES, AND FOR CHECKING THE ESCAPE OF POWDER GAS."
The object of my Invention is to construct a case or covering for a projectile,
which will give rotation and centration to it, and at the same time check the
escape of gas, and which is more easily manufactured and fixed than the means
before used for these purposes in the following manner-Instead of fixing gas
checks, either in the shape of metal rings round the outside of the projectile or in
the shape of a cup fixed only to or near the base of the projectile, I propose to
make by pressure or from sheets of copper, or of a combination of copper or spelter
with other metals, such as brass or pewter, a case or cylinder into which the pro-
jectile is inserted or dropped, and which is so long that it envelopes the whole or
greater part of the cylindrical part of the projectile, or so that it can be choked or
compressed round a portion of the cone of the projectile near its point.
This case is made thinner towards the fore part of the projectile, so as to take
the exact bore of the gun barrel, and thereby give to the projectile perfect cen-
tration and steadiness without allowing any appreciable windage.
The rotation is effected either by having the rear part of the case made some-
what thicker than the fore part, so that the thicker portion of it takes the rifling

page_text: of the gun barrel, or the rear part of the case can be extended beyond the base of
the projectile so that the explosion of the powder forces it to take the rifling;
or the bottom of the case can be so constructed that it is more convex (counting
from the powder charge) than the base of the projectile itself, so that when the charge
explodes such convex bottom is pressed or flattened against the base of the pro-
jectile, and forces its own peripherie or outer edge and the sides of the case
outwards in a radial direction from the centre line of the bullet, and thus makes
it fill the grooves of the rifling; or the case can be made with a combination of two
or all three of these modes of taking the rifling. In either way the metal of the
case which fills the grooves of the rifling will prevent the escape of powder gas.
If required a portion of the surface of the projectile can be made jagged or cut,
so as to prevent the projectile from sliding inside its case.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thorsten Wilhelm Nordenfelt in the Great Seal Patent Office on the
3rd May 1878.
THORSTEN WILHELM NORDENFELT, of 1, Saint Swithin's Lane, London, E.C.,
Civil Engineer. "AN IMPROVED METHOD OF GIVING ROTATION AND CENTRATION
TO PROJECTILES, AND FOR CHECKING THE ESCAPE OF POWDER GAS."
The object of my Invention is to provide a case or covering for a projectile which
will give rotation and centration to it, and at the same time check the escape of
gas, instead of fixing a gas check either in the shape of a metal ring round the
outside of the projectile or in the shape of a cup attached only to or near the base
of the projectile.
The cases or coverings which I employ are more easily constructed and applied
than the gas checks heretofore used.
In order that my said Invention may be most fully understood and readily
carried into effect, I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is an elevation, and Figure 2 is a section of a projectile having com-
bined with it, in accordance with my Invention, a case or covering which serves
to give rotation, to centre the projectile in the barrel, and to prevent the escape of
gas past it.
a, a, is the body of the projectile; it may be made of cast iron or other material
suited to the duty the projectile is intended to perform; b is the case or covering.
I prefer to make the case of brass or of copper, and to shape it by drawing upon
a mandril in the same way that some cases for small-arm cartridges are now
produced. The case is made of a size just to receive the projectile, and after the
projectile has been inserted it is passed through a die, which brings it accurately to
the proper diameter, at the same time that it closes it securely against the sides of
the projectile.

page_text: The projectile, shown in Figures 1 and 2, has a ring around its case at the base
end, which is left thicker than the remainder of the case for the purpose of taking
the rifling of the barrel. This arrangement is suitable where the barrel of a
breech-loading arm is chambered or enlarged at the breech end to receive the
cartridge.
Figure 3 is an elevation, and Figure 4 is a section of a projectile provided with a
case or covering of a slightly different form, the case here being extended beyond
the base of the projectile, forming a cup, the sides of which are forced outwards by
the explosion, and made to fill the grooves of the rifling. In these Figures also the
case is shown to be choked into a groove around the body of the projectile for
further security against the projectile being separated on firing from its case or
covering.
Figure 5 is an elevation, and Figure 6 is a section, showing another form of case
or covering, in which the base is made with a convexity standing away from the
base of the projectile, and which; when exposed to the pressure of the gases resulting
from the combustion of the powder or explosive, becomes more or less flattened,
driving the sides of the case into the rifle grooves, so as at once to ensure the
rotation of the projectile as it passes out of the barrel, and to prevent the escape of
the gas past the projectile.
Having thus described the nature of my said Invention, and the manner of
performing the same, I would have it understood that I claim, the combination
with a projectile of a metal case or covering, serving to give rotation, to centre
the projectile, and to prevent the escape of gas past it, substantially as described.
In witness whereof, I, the said Thorsten Wilhelm Nordenfelt, have hereunto
set my hand and seal, this Thirtieth day of April, in the year of our Lord
One thousand eight hundred and seventy-eight.
THORSTEN WILHELM NORDENFELT. ` (L.S.)