IMPROVEMENTS IN FIRE-ARMS
Year: 1876

page_text: LETTERS PATENT to John Wallace Duncan, of Southampton Chambers,
Chancery Lane, London, for the Invention of "IMPROVEMENTS IN FIRE-ARMS."
PROVISIONAL SPECIFICATION left by the said John Wallace Duncan at the
Office of the Commissioners of Patents on the 22nd June 1876.
JOHN WALLACE DUNCAN, of Southampton Chambers, Chancery Lane, London.
"IMPROVEMENTS IN FIRE-ARMS."
The first part of my Invention relates principally to sporting guns, and has for
its object to ensure closeness of shooting, and to increase the range and penetrating
power of the shot and yet retain the advantage of improved efficiency for shooting
with ball.
I obtain these results by fluting or grooving the barrel, whether of a muzzle or
breech-loading gun, in either of the following ways:
According to one way the barrel is bored cylindrical or nearly so throughout,
and is then fluted or grooved with straight longitudinal grooves, which are deepest
at the breech end, and become gradually shallower towards the muzzle, where the
bottom of each groove merges or becomes level with the intervening lands or cylin-
drical bore. Instead of the grooves finally merging with the surface of the bore at
the muzzle they may do so at a short distance from the muzzle.
A. modification of this system consists in making straight longitudinal grooves in
cylindrically bored barrels of equal depth throughout a portion of their length from
the breech towards the muzzle. Near the muzzle end the grooves become gradually
shallower until they finally merge imperceptibly with the plain part of the cylin-
drical bore. I leave three, four, or more narrow lands alongside the grooved portion
of the barrel.
Another way consists in making the grooves in barrels of cylindrical bore of a
wavy, zig-zag, or sinuous form, the curves being widest towards the breech end and
gradually or successively decreasing in pitch towards the muzzle, the wavy or
sinuous form being also gradually narrowed until each groove becomes quite
straight.
The depth of the wavy grooves is equal throughout their length, except towards
the muzzle end, where they become gradually shallower until they finally merge or
become level with the surface of the bore at about one, two, or more inches from the
[Price Gd.]

page_text: muzzle. I find it preferable to leave four or more narrow lands when the barrels
are grooved in this form.
A modification of this last-described method of grooving consists in making the
grooves deepest near the breech, and thence diminishing gradually in depth towards
the muzzle, until they finally merge with the surface of the bore at the muzzle, or
within a few inches of the muzzle.
The second part of my Invention relates to fire-arms generally, and it consists in
an arrangement whereby the hammer may, if desired, be caused to rebound to half-
cock by the elasticity of the main spring when the cock is snapped, but which may
be so adjusted that no rebound will take place if not desired. According to this
part of my Invention a head or T piece attached to an adjustable slide is introduced
in the lock, so that the said head or T piece may be so adjusted as to come between
an elongation of the top end of the main spring, and the limb of the tumbler near
where the swivel is jointed. In this position the tumbler will when the cock is
snapped come in contact with said head or T piece, and the hammer will be caused
to rebound. The T head may be withdrawn out of the way, if the rebounding
action is not required. The slide to which the T head is attached is provided with
a projecting stud or thumb piece passing through a slot in the lock plate to enable
the head to be adjusted as desired.
My Invention further consists in a folding device applied to the end of the lever
by which the breech holdfast is 'opened or closed. This device is more particularly
designed to be applied to breech-loading guns which have an under lever lying
along the trigger guard, but it may be applied to a top lever also. This lever is
usually formed with a projecting lump at its extremity by which to grip the lever
when opening or closing the breech, and when a gun having an under lever is
carried upon the arm the lump presses thereon and renders the gun unpleasant to
carry in this manner. My device consists of two folding leaves hinged to the lever
so as to open up like a butterfly's wings to form a grip or purchase by which to move
the lever in opening or closing the breech, the two leaves when not in use folding
down flat upon the lover so as not to hurt the arm when the gun is carried
as above-mentioned.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Wallace Duncan in the Great Seal Patent Office on the 22nd
December 1876.
JOHN WALLACE DUNCAN, of Southampton Chambers, Chancery Lane, London.
"IMPROVEMENTS IN FIRE-ARMS."
The first part of my Invention relates principally to sporting guns, and has for
its object to ensure closeness of shooting, and to increase the range and penetrating
power of the shot, and yet retain the advantage of improved efficiency for shooting
with ball.
I obtain these results by fluting or grooving the barrel, whether of a muzzle or
breech-loading gun, in either of the following ways:-
According to one way the barrel is bored cylindrical or nearly so throughout,
and is then fluted or grooved with straight longitudinal grooves which are deepest
at the breech end, and become gradually shallower towards the muzzle, where
the bottom of each groove merges or becomes level with the intervening lands
or cylindrical bore. There may be any number from three to twenty grooves and
lands in a 12-gauge bore barrel, and the depth of groove may be made at breech
end from, say, 005 of an inch to 020 of an inch, but I prefer a mean between
those. Instead of the grooves finally merging with the surface of the bore at the
muzzle they may do so at a short distance from the muzzle.
A modification of this Invention consists in making straight longitudinal grooves
in cylindrically bored barrels of equal depth throughout a portion of their length

page_text: from the breech towards the muzzle. Near the muzzle end the grooves become
gradually shallower until they finally merge imperceptibly with the plain part of
the cylindrical bore. The width of the lands need not be greater than 050 of
an inch if six or eight in number.
Another variation may be effected by grooving a 13-bore gauge barrel to the
depth of 018 of an inch about one inch and a quarter from the muzzle (com-
mencing with 0 at muzzle) and proceeding for one inch and a half more when the
depth of groove at or about this distance decreases to about 008 of an inch, which
then continues at that depth to the breech end or cartridge chamber, but considerable
variations from these proportions may be made.
Another form of grooving may be effected, say, in 14-gauge bore barrels of 690
of an inch diameter. The grooving may commence level with the cylindrical bore
at the muzzle and gradually curve into the maximum depth of 020 of an inch in
the course of an inch and a half from the muzzle, but from thence commence to
slope out of depth and become level with cylindrical bore in the course of two
inches more or three and a half inches from the muzzle. The gun barrel so treated
would be a smooth cylindrical bore, with the exception of the fluted portion ex-
tending over three and a half inches near the muzzle. Barrels may be grooved or
fluted in this manner with either longer or shorter extending cuts from the muzzle
in curved forms of depth having either shallower or a little greater depth of grooves
than mentioned above. The form of the contour of the grooving with regard to
depth may be partly a "Schiele's" antifriction curve that contracts the depth of the
grooves at the muzzle or other suitable angle.
Thick strong barrels of 16-gauge bored parallel diameter, 660 of an inch, may
be fluted or grooved from the end of the cartridge chamber to the depth of 035
of an inch with straight parallel grooves until within a few inches (more or less)
from muzzle, where grooving begins to become shallower and terminates at the
muzzle with a depth of about 017 of an inch, or thereabout, leaving the lands at
the muzzle in relief projecting about 018 of an inch above the extremity of the
grooves at the muzzle. I give these proportions as an example, but they may be
deviated from to a considerable extent and yet retain the character of my Invention.
The grooved portions of the barrels constitute the equivalent of smooth bore choke
guns, and the converging lands form a parallel cylindrical bore tending as stringers
to strengthen the barrels and partly preventing centrifugal action in the shot.
Compressed bullets with larger sized wads, when fitted nicely in size to the bore of
the parallel lands, shoot remarkably well with a very flat trajectory.
.
Another way consists in making the grooves in barrels of a cylindrical bore of a
wavy or lateral sinuous form, the curves being widest towards the breech end and
gradually or successively decreasing in pitch towards the muzzle, the wavy or
sinuous form being also gradually narrowed until each groove becomes quite straight
within about four inches of the muzzle. For breech-loading barrels of 11-gauge
bore, or 751 of an inch diameter and 30 inches long, there may be eight sinuous
wavy curves extending along the bore for 23 inches from the end of the cartridge
chamber. The pitch of the first wavy curve, which will sweep nearly half round
the bore and return, may be six inches, the pitch of the second sinuous or wavy
curve may be five inches, of the third a little more than four inches, of the fourth
over three inches, and the pitch of the fifth sinuous curve near two and a half inches,
and so on, so that by a decreasing pitch about eight sinuous curves, within a length
of 23 inches, will bring the wavy form to a straight line.
For the size of barrels mentioned above a mode of setting out the sinuous form
of grooving may be as illustrated in the diagram, Figure 1, which represents the
sinuous groove delineated on a plane surface. The lines a, a, show the diameter of
the bore of the gun, No. 11 gauge. The thick broken line b represents the sinuous
groove delineated on a plane, and the method of setting it out may be as follows:-
Draw the straight centre line c, and at the end next the cartridge chamber of the
barrel at a distance of 9/16ths of an inch (which is equal to one fourth the circumference
of the bore, at either side of the line c) set off the points d, and from a point e, 23 inches

page_text: distant from the cartridge chamber, draw the thin dotted lines f, f, to the points d.
The barrel being 30 inches long the point e will be four inches from the muzzle,
three inches being allowed for the cartridge chamber. Mark the pitch lengths of
the sinuous curves, as shown, and draw the sinuous curve to cross over the centre
line and touch the line f at one side, return and touch the line f at the other side,
and so on, until eight sinuous curves extending the whole length between the
lines from the cartridge chamber to the point e where they become gradually
contracted to a straight form, as shown.
The depth of the wavy grooves is equal throughout their length, except towards
the muzzle, where they become gradually shallower, until they finally merge or
become level with the surface of the cylindrical bore at about one or more inches from
the muzzle. The sinuous form may consist of nine lands 050 of an inch broad, and
the grooves be cut to a depth of 020 of an inch or more, commencing from cartridge
chamber end and continuing until within about an inch and a half from the muzzle,
where the depth becomes shallower until the grooves merge level with the cylin-
drical bore at or near the muzzle. I do not confine myself to the depth of grooving
stated above, as fluting may be made from 003 of an inch up to any depth that a
strong barrel will stand to effect advantages in shooting, neither do I confine
myself to the number or width of lands or grooves that I can make in a barrel; I
may also deviate considerably from the pitch of the sinuous curves mentioned, also
in the number of the curves, and also deviate from the width of sinuosities, and
may vary its extent of length, and to any suitable portion of the bore of barrels,
and yet retain the character of my Invention.
Another modification of the wavy lateral curved grooving may have the grooves
deepest at breech end, and become gradually shallower at or within a short distance
from the muzzle. In some barrels the depth may be made greater in one, two, or
more inches approaching the muzzle, and slope out shallow again level with the
cylindrical bore at the muzzle.
In the operation of fluting or cutting the grooves in the bore of gun barrels,
according to my Invention, with the existing rifling machines, it will be found best
to commence the cut at the muzzle end of the barrels, as the cutters are more safely
regulated to produce the requisite graduations in depth of the grooves by entering
into the cutting action from a level surface than in sloping out of a furrow at an
acute angle. In order to accomplish the sinuous form of grooving guide bars of
that shape will require to be fitted to the rifling machine.
In some instances when making up new barrels as fluted choke of 14-gauge
bore, for example, after being bored cylindrical they are heated red at the muzzle
when a steel drift made to fit the bore a few inches in length as a guide, but with
gradual increase of diameter at one end to 035 of an inch, or thereabout, above the
size of bore, is driven into the hot muzzle of the barrel to expand it to the required
forin.
The barrel is afterwards grooved with straight grooves of equal depth
throughout that just escape touching the widest expanded part of the barrel at the
muzzle. After being grooved a steel mandril to fit the bore is inserted at the
muzzle, when a split pair of circular dies that fitted the outside of barrel nozzle
before expansion are made to embrace the barrel at the beginning of the expanded
part, and by suitable mechanism drawn over it to contract the muzzle to its
original diameter of bore, when it will be found that the grooves slope out to the
shape of drift used.
The second part of my Invention relates to fire-arms generally, and it consists in
an arrangement whereby the hammer may, if desired, be caused to rebound to half-
cock by the elasticity of the mainspring when the lock is snapped, but which may
be so adjusted that no rebound will take place if not desired. According to this
part of my Invention a head or T piece attached to an adjustable slide is introduced
in the lock, so that the said head or T piece may be so adjusted as to come between
an elongation of the top end of the mainspring and the crane of the tumbler near
where the swivel is jointed. In this position the tumbler will when the lock is
snapped come in contact with said head or T piece, and the hammer will be caused

page_text: to rebound. The T head may be withdrawn out of the way if the rebounding
action is not required. The slide to which the T head is attached is provided with
a projecting stud or thumb piece passing through a slot in the lock plate to enable
the head to be adjusted as desired. The end of the T head slide is made thin
and tempered as a spring, and it has a small half round boss on it that springs into
either of two recesses in the lock plate on each side of its traverse to retain the T
head in proper position for half-cocking, or in the other position out of action.
This part of my Invention is illustrated in Figures 2 and 3, which show the T
head slide applied to two kinds of locks, and Figure 4, which represents the same
slide separately applied to the lock plate. g is the slide, and its head, which
comes between the elongation of the mainspring and the crane of the tumbler, as
shown, so that the latter will strike the T head and be caused to rebound to half-
cock by the elasticity of the elongated part of the mainspring with which the Thead
is in contact. When the T head slide is withdrawn out of the way the tumbler
will not strike the mainspring, and no rebounding action will take place, the T head
thus merely acting as a medium through which the tumbler may strike the elonga-
tion of the mainspring, and be caused to rebound when desired. i is the projecting
stud or thumb-piece fitted in a slot in the lock plate, from the surface of which it
projects; k is the small half round boss on the slide dropping into recesses in the
lock plate, as above described. The T head slide on each bar lock of a breech-
loading gun may be made the medium of putting into action an arrangement for
automatically cocking each hammer by the action of an open guard lever or pressing
forward lever, or a top lever in the act of opening the gun, and when full cocking
was not desired the half cocking action would come into operation, or further, if
desired, the hammers could fall as in a common lock.
My Invention further consists in a folding device applied to the end of the
lever by which the breech holdfast is opened or closed. This device is more
particularly designed to be applied to breech-loading guns which have an under
lever lying along the trigger guard, but it may be applied to a top lever also.
This lever is usually formed with a projecting lump at its extremity, by which
to grip the lever when opening or closing the breech, and when a gun having an
under lever is carried upon the arm, the lump presses thereon and renders the
gun unpleasant to carry in this manner.
My device consists of two folding leaves hinged to the lever so as to open up
like a butterfly's wings to form a grip or purchase by which to move the lever
in opening or closing the breech, the two leaves when not in use folding down
flat upon the lever so as not to hurt the arm when the gun is carried as above
mentioned.
Figures 5 and 6 represent cross sections of the end of the hand lever by which
the breech holdfast is opened or closed, provided with the folding device above
imentioned for obtaining a grip of the lever. Figure 5 shows the device folded
down flat and Figure 6 as opened out like butterflys' wings for use in moving the
lever. is the lever and m, m, are two leaves hinged together and to the lever
upon a common axis which is in the longitudinal direction of the lever. The.
leaves may be of any convenient length to afford a firm grip for the fingers.
Having described the nature of my said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is—
1st. Fluting or grooving gun barrels, bored cylindrical or nearly so, with straight
longitudinal grooves decreasing in depth towards the muzzle, as and for the
purpose specified.
2nd. Grooving gun barrels, bored cylindrical or nearly so, with wavy or sinuous
grooves decreasing in pitch and becoming gradually straight, also becoming
gradually shallower towards the muzzle, as and for the purpose herein set forth.
3rd. The employment of an adjustable slide fitted in the lock so that its end
may be interposed between the mainspring and tumbler for obtaining a rebounding
action at will, substantially as shown and described.

page_text: 4th. In breech-loading fire-arms the application to the end of the lever of the
butterfly folding device, consisting of two leaves hinged to the lever, as and for the
purpose specified.
In witness whereof, I, the said John Wallace Duncan, have hereunto set my
hand and seal, this Twenty-second day of December, in the year of our
Lord One thousand eight hundred and seventy-six.
JOHN WALLACE DUNCAN.
(LS)
Witness,
E HARVEY.