Process and Apparatus for Fixing Lining Tubes in the Rifled Barrels of Fire Arms.
Year: 1894

page_text: Date of Application, 14th Dec., 1894-Accepted, 2nd Feb., 1895
COMPLETE SPECIFICATION.
Process and Apparatus for Fixing Lining Tubes in the Rifled
Barrels of Fire Arms.
I, HEINRICH EHRHARDT, of Reichs Strasse 20 Dusseldorf, Germany, Engineer,
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 :-
My invention relates to a process and apparatus for fixing lining tubes in the
rifled barrels of fire arms for the purpose of reducing the calibre thereof, whereby
the said lining tube, being in the first instance made with a bore of smaller calibre
than that of the required finished bore, is expanded by means of internal pressure
so as to cause the metal thereof to enter and fill the rifling grooves of the barrel,
while the breech end of the lining tube is also expanded so as to correspond to the
configuration of the cartridge chamber.
For this purpose the lining tube, which may either be formed by turning and
boring out a solid bar, or preferably by the process of pressing and drawing
invented by me, or by any other known process, is formed with its external
diameter corresponding to the internal diameter of the barrel to be lined, while
the rear end is made of larger diameter either by reducing the other part by
The lining
turning, or by thickening by the upsetting process, or by other means.
tube having been introduced into the rifled bore of the barrel, the breech end is
then expanded so as to fill the breech chamber, either by forcing a mandril such
as a Fig. 1 of the accompanying drawings into the tube, the fore end of which and
of the barrel are made to bear against a fixed abutment to resist the forward
pressure of the mandril, which may be driven in either by a hammer or by
hydraulic or other pressure.
Or the expanding of the breech end can be effected by roller expanding tools
such as are used for expanding tubes in the tube plates of boilers.
The expanding of the metal of the tube into the rifling grooves of the barrel
is effected either by internal liquid or gaseous pressure, or by drawing through it
one or more mandrils of suitable gradually increasing diameters.
As before stated, the bore of the lining tube is made as much smaller than the
required finished calibre as is necessary for allowing the metal of the tube when
expanded to fill out the rifling grooves of the barrel, as also, if necessary, to allow
of a certain compression of the metal.
In the accompanying drawing,
Fig. 1 shews the barrel with the lining tube s introduced and supported by the
abutment b, and with the mandril a for expanding the breech end about to be
forced in;
Fig. 2 shews the barrel and tube with the breech end expanded ;
Fig. 3 shews the barrel and tube supported by the abutment c, with a mandril d
about to be drawn through in the direction of the arrow for expanding the tube
into the rifling grooves.
There may be, according to requirements, two or more successive mandrils
of gradually increasing diameters in which case these may be combined on one
and the same draw bar as shewn at Fig. 4. In this case also, another form of
support is shewn for the barrel, this being screwed by means of its threaded
breech end into a socket with a head e which butts against the fixed abutment
plate f. The abutment plate might also be provided with a screw thread into

page_text: which the breech end of the barrel is screwed directly without the intervention of
the socket. The drawing through of the mandrils can be effected on ordinary
draw benches such as screw draw benches, chain draw benches, rack bar benches,
or hydraulic drawing machinery.
The drawing process can also be reversed, the drawing mandril or mandrils
being fixed, and the barrel with the lining tube drawn over it or them.
Fig. 5 shews the barrel and lining tube after the drawing operation.
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. The process of lining rifled barrels of fire arms with tubes for reducing the
calibre thereof, whereby the excess of the metal of the lining tube is forced into
the rifling grooves of the barrel by internal pressure exerted either by fluid under
pressure or by a mandril or several mandrils with gradually increasing diameters,
substantially as described.
2. For carrying out the process referred to in the preceding claim, the use of a
draw bar with which are combined two or more mandrils of gradually increasing
diameters, substantially as described.
Dated this 14th day of December 1894.
ABEL & IMRAY,
Agents for the Applicant.