Improvements in Ordnance and other Rifled Fire-arms.
Year: 1896

page_text: Date of Application, 7th Sept., 1896-Accepted, 19th Dec., 1896
COMPLETE SPECIFICATION.
Improvements in Ordnance and other Rifled Fire-arms.
I, MIGUEL GARCIA DE LOMAS, Captain of Artillery in the Royal Spanish
Marine, residing at Placencia de las Armas, in the Province of Guipuzcoa, in the
Kingdom of Spain, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The object of this invention is to provide for preventing erosion in cannon or
ordnance and other rifled fire-arms whilst augmenting their ballistic effect, and the
said invention is based on the method of making the bore of such fire-arms conical
or taper, both in respect of the diameter at the lands and grooves of the rifling and
in respect of the corresponding progressive diminution of the width of the lands
and grooves.
In the accompanying drawing,
Fig. 1 is a plan, and Fig. 2 a longitudinal section of a 10-centimetre gun of
conical bore.
Figs. 3 and 4 are two sections, drawn to an enlarged scale, of the gun on two
planes, perpendicular to the axis and passing through the extremities of the bore.
The differences of width of the land and of the grooves can be seen therein.
The conical form or contour of the improved cannon, that is to say, the conical
outline of the bore, consists in that the bore of the cannon commences at the
breech A with a diameter several tenths of a millimetre greater than the desired
calibre of the gun, and terminates with the exact calibre at the muzzle B of the
gun. The rifling is produced in the ordinary way, introducing only such variations
as are necessary to give the bottom of the grooves or channels an inclination equal,
at least, to that of the bore, and so that their width at the beginning is greater
than at the end, that is to say, at the muzzle of the weapon.
The principal object of this invention, as well as its theoretical aspect as
compared with guns with cylindrical bore, is as follows:
Heretofore, in all rifled fire-arms, the cylindrical form or contour has been
retained for the part of the bore traversed by the projectile, which latter is
provided with a ring of copper or other more ductile metal, of a greater diameter.
This arrangement has for its object that, when one engages with the other, the
resistance to the motion of the projectile shall increase as the projectile advances,
thus promoting the complete ignition of the charge, avoiding escape of the gases to
the space in front of the projectile and imparting to the projectile a sufficient
velocity of rotation to enable it to maintain its proper stability during its flight or
trajectory and so obtain greater accuracy in firing; but, with this cylindrical
contour it is only possible to realise the two first objects when the movement of the
projectile begins, and when the rifling takes or engages with the driving-band,
because, as the whole of the bore is cylindrical, its form is the same at the
beginning as at the end of the travel, and this is the form which the driving-band
consequently assumes and which it retains until the exit of the projectile from the
muzzle, therefore, forcing of the driving-band into the grooves of the gun does not
take place after the first moment, thus giving rise to small leakages of gas
between the bottom of the grooves and the driving-band, which leakages, after a
certain number of shots have been fired, produce erosion in the gun, even to the
extent of rendering it useless for service.

page_text: Conical bores avoid this inconvenience, for when the motion of the projectile has
commenced, its driving-band is in the part where the diameter is the greater, and
where the grooves are wider, thus offering a slight resistance to its advance, but as
the motion of the projectile continues, the driving-band is compressed in the
direction of its circumference, the action of which tends to close or reduce the
spaces therein for receiving the lands of the rifling, and to enlarge the projections
which slide in the grooves of the bore, which spaces and projections are enlarged
or lengthened by the pressure which the gases exert on the base of the projectile,
by having to overcome at each instant the resistances which the driving-band
offers to its successive deformation, and it is in this way that it is possible to obtain
the constant and gradual increase of resistance of the projectile in its passage
through the bore. These successive deformations which the driving-band
experiences, place it at each instant in conditions identical with those which obtain
in guns with cylindrical bores when a similar projectile is begining to move therein,
that is to say, in the true conditions for obturation, consequently avoiding escapes
of gas which even if still existing by reason of the allowance for wear would be
much less, and thus the life of the weapon is lengthened.
Further, by reason of the resistance which the projectile offers continually during
its advance, it results that the charge ignites in much greater quantity than in guns
of cylindrical bore, and the initial velocity of the projectile is consequently
increased.
The rotation of the projectile is obtained by either form of contour, but, since
the velocity of rotation is a function of that of translation, and since the latter can
be made greater with the conical outline than with the cylindrical, it is obvious
that the velocity of rotation will also be greater with the first named form or
outline than with the second.
What has just been said on the subject of initial speed and rotation, also applies
'as regards accuracy of firing, so far as that depends on the rotation of the
projectile.
From what has just been said, it is considered that the following advantages are
obtained by using the conical outline or contour :-
1. Perfect obturation.
2. Increase of the initial velocity.
3. Increase of the velocity of rotation.
4. Greater accuracy in firing.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A cannon or piece of ordnance or other rifled fire-arm having the bore thereof
conical or taper from the chamber to the muzzle, substantially as, and for the
purposes herein before described.
2. A cannon or piece of ordnance of other rifled fire-arm having the bore thereof
conical or tener from the chamber to the muzzle both in respect of the diameter at
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A cannon or piece of ordnance or other rifled fire-arm having the bore thereof
conical or taper from the chamber to the muzzle, substantially as, and for the
purposes herein before described.
2. A cannon or piece of ordnance of other rifled fire-arm having the bore thereof
conical or tener from the chamber to the muzzle both in respect of the diameter at
the lands and grooves and in respect of the corresponding progressive diminution
in the width of the lands and grooves, substantially as hereinbefore described and
for the purpose specified.
Dated this 7th day of Sontember 1896
ABEL & IMRAY,
Agents for the Applicant.