IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN KINDS OF GUN AND PISTOL BARRELS, AND IN MACHINERY OR APPARATUS EMPLOYED THE SAID MANUFACTURE.
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by John Plumb Clabrough at the Office
of the Commissioners of Patents on the 23rd March 1876.
JOHN PLUMB CLABROUGH, of Birmingham, in the County of Warwick, Gun
Manufacturer. "IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN KINDS OF
GUN AND PISTOL BARRELS, AND IN MACHINERY OR APPARATUS EMPLOYED
THE SAID MANUFACTURE.'
"
IN
My Invention has reference to gun and pistol barrels of the kind commonly
called choke bore barrels, that is, barrels in which the internal diameter of the
barrel is slightly contracted at and near the muzzle.
My said Invention consists of the process herein-after described whereby the
required contraction of the muzzle end of the barrel is produced, and the machinery
or apparatus employed in conducting the said process.
I will describe the process of manufacturing choke bore gun and pistol barrels
according to my Invention in conjunction with the machinery or apparatus I
employ. I first make the barrel in the ordinary way, the bore of the barrel being
cylindrical from end to end. I take a rod of somewhat greater length, and of
smaller diameter than the barrel. This rod has a head or shoulder at one end
of larger diameter than the barrel. The other end of the said rod is made into a
screw. I pass the said rod into the barrel to be operated upon, the screwed end
being introduced at the breech end of the barrel, and when the rod is pushed home
the head bears against the open breech end of the barrel, and the screwed end of
the rod protrudes from the muzzle end. I take a strong nut, somewhat like an
ordinary screw nut, and having in its axis a hole slightly conical, one end of
the hole being sufficiently large to pass on to the extreme end of the barrel, the other
end of the hole being smaller, having the diameter to which it is necessary to to
reduce the external diameter of the barrel in order to produce the required con-
traction or choking of the bore of the barrel. I pass this nut over the screwed
end of the rod, the wider end of the hole in it being turned towards and made to
take upon the end of the barrel. I then place a screw nut furnished with arms
for turning it upon the screwed end of the rod, and by turning the said screw nut
cause it to advance upon the screwed rod and to push before it the nut having the
conical hole. As the latter is advanced upon the barrel it compresses the part over
which it passes, and reduces the diameter of the interior of the barrel. Although
I have described the use of one nut with a conical hole for compressing the muzzle
end of the barrel, yet I prefer to use several of the said nuts beginning with the
one having the largest conical hole, and continuing the process of the successive use

page_text: of others having progressively smaller conical holes. By thus producing the
required contraction gradually there is little risk of injuring the barrel, and any
required degree of choking may be readily produced. The contraction may be
carried to any distance by interposing between the acting nut described and the
screw nut on the end of the rod one or more loose nuts capable of sliding freely
on the barrel. By the use of these loose nuts the acting nut may be forced to any
required distance on the barrel. In order to remove the acting nut from the barrel
the muzzle end of the barrel is dropped into a slot in a strong rectangular metal
frame against the inner side of which the nut on the barrel abuts. A screw passes
through the opposite side of the frame, and a stopper being put on the muzzle of
the barrel for the screw to act against, the turning of the said screw forces the
barrel from out the nut. The figure of the compressed part of the bore may be
perfected, and its size determined with the extremest nicety, by means of a cutter
constructed as follows:-The said cutter consists of a rod, near one end of which is
a longitudinal slot in which is a cutting tool fixed by its rear end to one end of
the slot. The other or fore end is raised to any required degree from the slot by
means of a screw in the axis of the rod. The advancing end of this screw, passing
under the fore moveable end of the cutting tool, raises it more or less from the
slot. The rod has a support or covering of wood on the part opposite to that in
which the slot is made. By the rotating action of this cutter, adjusted by means
of the axial screw, the contracted part of the bore can be cut to the required
extent. This cutter may be employed to operate upon choke bore barrels made in
other ways.
My Invention is applicable to rifled as well as to plain gun and pistol barrels.