CERTAIN IMPROVEMENTS IN BREECH- LOADING FIRE-ARMS.
Year: 1871

page_text: LETTERS PATENT to Silvanus Frederick Van Choate, of Boston, in
"
the County of Suffolk, and State of Massachusetts, United States of
America, for the Invention of CERTAIN IMPROVEMENTS IN BREECH-
LOADING FIRE-ARMS.
"
the County of Suffolk, and State of Massachusetts, United States of
America, for the Invention of "CERTAIN IMPROVEMENTS IN BREECH-
LOADING FIRE-ARMS.
"
Sealed the 11th August 1871, and dated the 16th February 1871.
PROVISIONAL SPECIFICATION left by the said Silvanus Frederick Van
Choate at the Office of the Commissioners of Patents, with his
Petition, on the 16th February 1871.
I, SILVANUS FREDERICK VAN CHOATE, of Boston, in the County of
Suffolk, and State of Massachusetts, United States of America, do hereby
declare the nature of the said Invention for CERTAIN IMPROVEMENTS IN
BREECH-LOADING FIRE-ARMS," to be as follows:-
65
These improvements have for their basis a class of breech-loading
fire-arms of which the Prussian needle gun and the French chassepôt
are notable instances, and in which the breech-loading mechanism
consists of a cylindrical bolt sliding longitudinally within a channel
formed in the frame or stock in rear of the barrel and in axial alignment

page_text: "
with its bore, such bolt carrying not only the firing pin for exploding the
fulminate of the cartridge, but containing the greater part or the whole
of the lock mechanism with the exception of the trigger, but while arms
of this character require paper or cloth cartridges I have adapted my
present one to the use of metallic cased cartridges or "fixed ammuni-
tion so called, the use of this ammunition in an arm of this nature
enabling me not only to produce the arm at much less cost but to
entirely avoid the clogging and derangement of the breech-loading
mechanism by reason of the escape of gas and dirt from the rear
end of the barrel to which the arms heretofore produced have been
subjected.
The improvements herein embodied relate, first, to the peculiar forma-
tion of the forward end of the breech bolt, whereby the spent cartridge
case is extracted without the mechanical appliances now considered
indispensable, the first portion of this Invention consisting in creating a
concavous enclosure in the forward end of the breech which receives the
rear end of the cartridge shell, whose form is adapted to this cavity, and
in producing in one side of said cavity a slight depression, into which
the cartridge shell is forced by the explosion of the cartridge. This
depression serves to take a hold upon the shell sufficient to withdraw it
from the chamber of the barrel upon the retraction of the breech bolt.
A small block or tripper is pivotted to the bolt and below its enclosure in
such manner that upon impinging against the trigger of the arm to
which it is brought by the retraction of the said bolt the
from the roadway of the latter and falls to the ground. Another very
important office performed by the said depression is the griping of the
shell with sufficient tenacity to enable the latter to be partially rotated
by the action of the breech bolt in unloading, to loosen its hold upon the
interior of the barrel, and permit it to be easily removed,
shell is ejected
Secondly. These improvements relate to the peculiar form and dis-
position of a tripper or ejector which is pivotted to the forward end of
the breech bolt and to the action of the trigger upon it when brought
in contact with the same, whereby the spent cartridge shell is thrown
from the arm. The tripper plays within a slot formed in the forward
end of the breech bolt, and communicating with its concavity. This
slot and tripper are arranged by preference diametrically opposite the
small depression before mentioned, and the tripper is pivotted to the
bolt in such manner as to oscillate upon the pivot. The form of this

page_text: tripper is such that it presents a flush surface with the enclosure or
concavity when the breech is locked in firing position, and the rear end
of a cartridge case rests in such enclosure. The advance of the breech
bolt serves to deflect the tripper into its normal position. As the breech
is retracted after firing the arm the shell by means of the depression or
score is withdrawn from the barrel with the breech bolt until the latter
reaches its loading position, at which point the tripper is brought in
contact with the upper end of the trigger, and the shell is thrown with
a quick movement from the cavity.
Thirdly. These improvements relate to an arrangement of the breech
bolt, lock mechanism, and trigger of the arm, whereby the latter in
addition to its ordinary functions of preventing the unlocking of the
breech bolt until the exploding pin is brought to a full cock serves in
connection with a channel formed in the under side of the bolt as a
guide to ensure the correct position of the latter while in movement,
either rearward for the purpose of reloading or forward to close the
cartridge chamber of the barrel. The firing pin is so formed and com-
bined with the breech bolt that upon bringing it to a full cock its
restraint upon the trigger is removed, and the bolt suffered to be
partially revolved and unlocked. It is a characteristic and important
feature of my present arm that its entire lock and exploding mechanism
is isolated completely from the cartridge and the trigger until the bolt
is driven forward and locked in firing position, the trigger merely
serving to release the firing pin when the latter is advanced to meet it,
and not as in the needle and chassepôt arms to cock the same.
Fourthly. These improvements relate to the combination and arrange-
ment of the firing pin and the breech bolt and a spring catch for cocking
or releasing the said pin, the spring being operated by a trigger when
the breech bolt is locked in firing position, the said spring catch or
"sear," as it may be termed, serving to maintain the firing pin at a full
cock while the breech bolt is retracted, or at full or "half cock " while
it is advanced and the arm is loaded.
$$
sear
Fifthly. These improvements relate to a novel mode of connecting
the spring catch or " of the lock to the breech bolt, and in com-
bining with the two a tubular nut which screws upon the end of the
breech bolt, and through which the firing pin plays, the latter being
furnished with a hammer or cock, and the whole being so arranged that

page_text: upon unscrewing the nut the sear is detached and the firing pin removed
without further trouble.
The firing pin is formed with two collars or studs disposed about
midway between its two extremities, a spiral or other spring being
coiled about the pin and between the rearward collar or abutment and
the nut which encloses the rear end of the breech bolt, and serves by
its extension to drive the firing pin and exploder forward to such an
extent that the latter shall strike and explode the fulminate of the
cartridge.
The said spring catch is formed upon its inner face with an inclined
or sloping projection, the disposition of which with respect to the collars
or studs being such that when the firing pin is advanced to its
greatest extent the rearward collar shall be slightly in advance of such
projection, while the forward collar is at such time straddling the upper
end of the trigger, the said collar being formed with a passage or slot
to enable this to be done.
The trigger thus enclosed by and locked to the pin, which in turn
cannot revolve within the breech bolt, prevents any rotation or unlocking
of the latter until the said firing pin is fully cocked, which retracts the
stud from about the trigger and leaves both free to revolve.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Silvanus Frederick Van Choate in the Great Seal
Patent Office on the 16th August 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, SILVANUS
FREDERICK VAN CHOATE, of Boston, in the County of Suffolk, and State
of Massachusetts, United States of America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of February, in the year
of our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Silvanus Frederick Van Choate, Her
special licence that I, the said Silvanus Frederick Van Choate, my
executors, administrators, and assigns, or such others as I, the said
Silvanus Frederick Van Choate, my executors, administators, and assigns,

page_text: should at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "CERTAIN IMPROVEMENTS IN BREECH-LOADING FIRE-
ARMS," upon the condition (amongst others) that I, the said Silvanus
Frederick Van Choate, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Silvanus Frederick Van Choate, do
hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement taken in connection with the
Drawing which illustrates it, and in which Figures 1, 2, and 3 are
vertical and longitudinal sections; Figures 4, 5, and 6 are vertical and
transverse sections; and Figure 7, a horizontal section of a portion of a
fire-arm containing my improvements; Figure 8 is a perspective view
of the firing pin; Figure 9, a perspective view of the sear; and Figures
10, 11, and 12, modifications of the arm to be herein-after explained;
Figure 13 is a transverse section of the arm on a reduced scale.
These improvements have for their basis a class of breech-loading
fire-arms of which the Prussian needle gun and the French chassepot
are notable instances, in which the breech-loading mechanism consists of
a cylindrical bolt sliding longitudinally within a channel formed in the
frame or stock in rear of the barrel and in axial alignment with its
borc, such bolt carrying not only the firing pin for exploding the
fulminate of the cartridge but containing the greater part or the whole
of the lock mechanism with the exception of the trigger; but while
arms of this character require a paper or cloth cartridge I have adapted
my present arm to the use of a metallic cased cartridge or
"fixed
ammunition," so called, the use of this ammunition in an arm of this
nature enabling me not only to produce such arm at much less cost,
but to entirely avoid the clogging and derangement of the breech-
loading mechanism by reason of the escape of gas and dirt from the rear

page_text: end of the barrel, to which the arms heretofore produced have been
subjected.
1. The nature of the improvements herein embodied consists, first,
in the peculiar formation of the forward end of the breech bolt, whereby
the spent cartridge case is extracted without the mechanical appliances
now considered indispensable, the first portion of this Invention consisting
in creating a concavous enclosure in the forward end of the breech bolt
which receives the rear end of the cartridge shell, whose form is adapted
to this cavity; and in producing in one side of said cavity a slight
depression, into which the cartridge shell is forced by the explosion of the
cartridge, the depression serving to take a hold upon the shell sufficient
to withdraw it from the chamber of the barrel upon retraction of the
breech bolt as herein-after stated, a small block or tripper being pivoted
to the bolt and below its enclosure in such manner that upon impinging
against the trigger of the arm to which it is brought by the retraction
of said bolt the shell is ejected from the roadway of the latter and falls
to the ground. Another very important office performed by the depression
being that it grips the shell with sufficient tenacity to enable the latter
to be partially rotated by the action of the breech bolt in unloading,
and loosen its hold upon the interior of the barrel.
2. And secondly, these improvements consist in the peculiar form and
disposition of a tripper or ejector which is pivoted to the forward end
of the breech bolt and the action of the trigger upon it when brought
in contact with the same, whereby the spent cartridge shell is thrown
from the arm, the whole being as herein-after stated.
3. And thirdly, these improvements relate to a certain arrangement
of the breech bolt, lock mechanism, and trigger of the arm, whereby the
latter serves in addition to the ordinary functions required of it to
prevent unlocking of the breech bolt until the exploding pin is brought
to a "full cock," but also serves in connection with a channel formed
in the under side of the bolt as a guide to ensure the correct position
of the latter while in movement, either rearward for the purpose of
reloading, or of forward to close the cartridge chamber of the barrel, the
firing pin being so formed and combined with the breech bolt that upon
bringing it to full cock its restraint upon the trigger is removed and
the bolt suffered to be partially revolved and unlocked, it being a
characteristic and important feature of my present arm that its entire
lock and exploding mechanism is isolated completely from the cartridge

page_text: and the trigger until the bolt is driven forward and locked in firing
position, the trigger merely serving to release the firing pin when the
latter is advanced to meet it, and not as in the needle and chassepot arms
to cock the same.
4. And fourthly, these improvements consist in the combination and
arrangement of the firing pin and the breech bolt, and in addition
thereto of a spring catch for cocking or releasing said pin, the spring
being operated by a trigger when the breech bolt is locked in firing
position, the said spring catch or sear as it is termed serving to
maintain the firing pin at full-cock while the breech bolt is retracted,
or at full or "half-cock" while it is advanced and the arm is loaded.
"
5. And fifthly, these improvements consist in a novel mode of con-
necting the spring catch or "sear" of the lock to the breech bolt, and
in combining with the two a tubular nut which screws upon the end
of the breech bolt, and through which the firing pin plays, the latter
being furnished with a hammer or "cock," and the whole being so
arranged that upon unscrewing the nut the "sear" is detached and the
firing pin removed without further trouble.
The Drawing accompanying and making part of this Specification
represents at A a portion of a fire-arm of full size, of which B is the
barrel; C, the frame or "receiver" in which the breech bolt slides; D,
the stock; E, the trigger; F, the trigger strap; G, the trigger guard;
and H, the stock screw, such parts being arranged essentially after the
manner of fire-arms of the class to which allusion has herein-before been
made, the bore of the barrel being indicated by the letter a and its
cartridge receiving chamber at b.
In carrying out the improvements which embody my present Inven-
tion I produce a cylindrical bolt I of about 8 inches in length and of
a diameter somewhat exceeding that of the cartridge chamber 6 of the
barrel, such bolt traversing a segmental channel or roadway c created
in the receiver or frame C before mentioned, a lateral opening & being
made in such channel in order to permit of ready insertion of the
cartridge into the barrel, or the expulsion of the spent shell of such
cartridge. The rear boundary. of this opening or depression d serves as
an abutment or recoil seat to maintain the breech bolt in secure position
when locked thereto, this locking of the bolt being effected by a rib e
produced upon it as shown, and provided with a handle ƒ departing
from it at right angles to its axis, substantially after the manner of

page_text: the Prussian needle gun before referred to, the disposition of the rib and
handle being such that when the latter is brought into a vertical position
as shown in Figure 1 of the Drawing, the rib is in alignment with the
opening d of the roadway c, and is released from contact with the recoil
seat, thus permitting of unlocking and rearward movement of the
bolt and its adjuncts. The rib e is of such size as to fill the lateral
opening d, and present a uniform and pleasing union and finish of the
surrounding parts. The forward end of the breech bolt which extends a
short distance into the cartridge chamber is concavous, as shown at i, the
form of the concavity being semi-spherical or approximately so, in order to
enclose the end of the cartridge shell, whose rear end is of a similar shape
and size, this form being adopted in order that I may be enabled readily
to expel such shell, whose ejection is effected as herein-after stated.
1. In order to seize the spent cartridge shell, and by this act carry
out the first clause of these improvements, I create in the wall of the
concavity i near its outer edge, and upon that side thereof immediately
adjacent to or in alignment with the ribe and its handle a small depression
or score k, as shown in Figure 1 of the Drawing, this score being of
such a shape and depth as to retain a hold upon the cartridge shell
when by the explosion of the charge of the latter a small portion of
the metal composing it has been driven into such score. This mode of
retracting the shell is productive of a very important advantage, as it
leaves no opening for the escape of gas and dirt from the rear end of
the barrel.
2. in the Drawing denotes a small lever or tripper playing within a
slot m formed in the forward end of the breech bolt and communicating
with its enclosure i, this slot and tripper being arranged diametrically
opposite the score k before mentioned, and the latter pivoted to the
bolt in such manner as to oscillate upon this pivot. The form of
this tripper, which is shown in Figure 3, is such that it presents a
flush surface with the inclosure i, when the breech is advanced and
locked in firing position and the rear end of a cartridge case rests in
such enclosure, the advance of the breech bolt in driving a cartridge
within the barrel serving to deflect the tripper into this which may be
considered its normal position. As the breech is unlocked and retracted
after firing the arm the shell by means of the score k is withdrawn
from the barrel and carried with the breech bolt until the latter reaches
its extreme loading position, at which point the tripper is brought

page_text: in contact with the upper end of the trigger E, and forced into the
position shown in Figure 3 of the Drawing, by which means the shell is
thrown with a quick movement from out of the cavity i.
It will be observed that when the breech is locked in firing position
as shown in Figure 2, the tripper and score k are in a plane hori-
zontal to the vertical axis of the barrel and receiver, and that when
the said breech bolt is revolved in the arc of a circle to the extent of
90° in the direction of the arrow thereon, as shown in Figure 13, the
said tripper and score are brought into vertical alignment with the bore
of the barrel, the score being uppermost. This twisting motion of the
breech bolt is imparted to the spent shell seized by such bolt and effects
a very important function, since it is well known that if the spent
shell of a fire-arm is started to a small extent in any direction its hold
upon the chamber of the barrel is loosened and its extraction there-
after easily effected. The tripper and the functions performed by it
constitute the means for carrying out the second portion of theso
improvements.
3, 4, & 5. In carrying out the third, fourth, and fifth clauses of these
improvements in the order herein first classified, I bore entirely through
the breech bolt I a concentric cylindrical hole m, whereof the rear half
is largest for reception of the firing pin, which is represented in the
Drawing at n, the forward portion of this bore or that nearest the barrel
being reduced in diameter for about one inch rearward from the end
of the bolt, and containing the exploder which plays within it, this
exploder being represented at o as an attenuated rod or needle which
projects forward from the end of the firing pin, and is formed integral
with it. The firing pin n extends rearward entirely through the breech
bolt and is provided at this extremity with a knob or cock p, this cock
serving to set the firing pin at half or full cock, as the case may be.
The firing pin n is formed with two collars or ears q, r, disposed about
midway between its two extremities, and situated about three-eighths
of an inch apart, a spiral or other spring a being coiled about the pin,
and between the rearward collar or abutment and the nut / which
encloses the rear end of the breech bolt, and serving by its extension
to drive the firing pin and exploder forward to such an extent that the
latter shall strike and explode the fulminate of the cartridge. The
nut last above mentioned is shown in the Drawing as a tubular
sleeve, provided with a female screw to screw upon a male screw

page_text: cut upon the end of the breech bolt, and with a hole through its rear
end, in which the extremity of the firing pin plays as before-mentioned.
A rectangular open orifice or slot is cut in the lower part of the
breech bolt, and opening into its bore, this slot being at right angles
to the axis of the handle f and to the greatest plane of the tripper 1,
and occupying about one half the entire length of the breech bolt,
or extending from the forward collar 9 of the firing pin (when the
latter is released from the sear) to the extreme rear end of the bolt.
This slot serves to guide the movements of the firing pin and main-
tain it at all times in the same axial alignment with respect to the
bolt which encloses it, and this slot is covered or partially filled by
a spring catch a¹ of equal width which enters it, the rear end of this
catch, whose outer face is the segment of a circle, corresponding in
extent to that of the bolt being formed with two shoulders or abutments
and a sectional male screw which is enclosed within the nut t, as repre-
sented, and by it securely held in proper position, the outer face of this
catch being flush with the circumference of the breech bolt, and forming
with the latter a perfect cylinder. The spring catch a¹ is formed upon
its inner face with an inclined or sloping projection w, as shown in
Figure 2 of the Drawing, the disposition of this hook with respect to
the collars or studs q and being such that when the firing pin is
advanced to its greatest extent the stud r shall be slightly in advance
of such hook, while the forward stud q is at such time straddling the
upper end of the trigger E, the stud being formed with a passage or
slot x to enable this to be done. The trigger thus enclosed by and
locked to the firing pin which in turn cannot revolve within the breech
bolt, prevents any rotation or unlocking of the latter until the said firing
pin is fully cocked, which act retracts the stud q from about the trigger
and leaves both bolt and pin free to revolve. This full cocking of the
firing pin is effected by seizing hold of the cock with the thumb and
retracting it until the collar q has passed by and been caught by the
hook w of the spring catch or sear a¹, the springs serving to drive the
firing pin suddenly forward when it is released from the control of the
sear by the action of the trigger.
The trigger of this arm is a compound one, and its construction and
operation is as follows:-In addition to its finger portion 6', which is of
ordinary form, and besides being pivoted to the trigger strap F in the
usual manner of fire-arms, it is formed with an arm c¹ which slopes

page_text: forward at a rising acute angle with respect to the trigger plate, and to
the free extremity of this arm c¹ the lower end of an upright block d¹ is
pivoted, such block rising through an aperture e¹ made in the lower part
of the stock and receiver of the arm, and into the road bed of the breech
bolt, and it is this block which has herein-before been alluded to as the
upper part of the trigger against which the tripper / abuts when expelling
the empty shell. The extreme upper part of this block d¹ has an over-
hanging rearward lip d³, and it is this lip which effects the release of the
firing pin at the proper time.
"
"
We will suppose the firing pin to have been retracted to its utmost
extent and set at full cock, the breech bolt unlocked and retracted, the
cartridge inserted within the barrel, and the breech bolt subsequently
advanced and locked in position, it being observed that by the last act
the forward end of the sear has been brought below the lip d³. As the
breech bolt is advanced the spring catch is prevented from falling away
from and releasing the firing pin by the roadway as the catch bears directly
upon it, consequently no accidental release of the pin can take place, for
it is only when the breech bolt has reached its extreme forward position
that the catch coincides with a depression f¹ cut in the road bed of
sufficient depth to allow it to recede from the collar q; at this time
however the catch or sear is entirely protected by the receiver of the
arm and cannot be actuated until struck by the trigger, which act takes
place as follows:-As the breech bolt is turned in the arc of a circle
90 degrees to the right of the operator in the act of locking it as before
explained, the nose or point g¹ of the catch or sear a¹ is brought directly
under the lip d² of the trigger or its block d', consequently a pull upon
the finger portion of the trigger will release the firing pin from the
control of the sear and permit its spring to advance it and explode the
cartridge. The collar or projection r, as before stated, effects the half-
cock of the firing pin, and when in this position a pull upon the trigger
has no effect, as it, the trigger, is at this time situated within the slot or
shelf groove of the collar q, the said trigger being formed with lateral
The half-cock of the
ears to enter this groove and arrest its descent.
firing pin also prevents rotation of the breech block by means of the
slot in the aforesaid collar, so that such half-cock is the safest position in
which the arm can be carried, for it is only when it is at full cock that
the control of the trigger upon the firing pin is released and the breech
bolt permitted to rotate. As the spring catch cannot be lowered until
by the locking of the breech bolt it, the catch, reaches the depression f¹,

page_text: and as the firing pin cannot be released until the catch is lowered, it
follows that the impact of the spring upon the bottom of the roadway of
the breech bolt absolutely prevents release of such pin, until as before
stated the sear reaches the depression f¹, which it only does when the
breech bolt is in firing position and is locked, and not then, until by a
partial revolution of the bolt and firing pin the sear or catch has been
brought into contact with the trigger or into the path of movement of
the same.
In the above arrangement of the breech block, firing pin, spring, and
trigger with their accessories will be seen the means of carrying out the
third and fourth portions of these improvements, and in the combination
and arrangement therewith of the sectional spring catch a and tubular
nut t, the fifth and last classified portion of said improvements. An
arm as above described is extremely simple, durable, and effective.
Owing to the very few parts composing it, and the fact that these com-
ponent parts are chiefly produced by boring and turning in a lathe, my
present arm may be manufactured at very low cost; while in addition to
these merits it possesses no unsightly protuberances or bulky unwieldly
proportions to interfere with the most approved manual, but is
symmetrical in general form, and smooth and even in finish, with no
loose joints for permitting sand or dirt to find its way to its working
parts. This arm will also stand the unreasonable test now required of
cutting off a portion of the rear end of the cartridge shell, as the breech
bolt requiring no mechanical appliances to seize the shell entirely fills
the breech chamber at the end of the barrel. To withdraw the brecch
bolt entirely from the cam it is only necessary to lower the trigger
block d to its lowest point, which will permit the said breech block to
be drawn directly backward and out of its receiver.
I have contemplated a modification of the mode herein shown for
controlling the movement of the sear and trigger, or for setting the arm
at half-cock, which consists in forming a short shelf or lip upon the
upper side of the forward end of the sear, this lip extending horizontally
rearward and being so disposed as to lock into a groove or cross channel
cut across the forward face of the collar r, when the latter has been
retracted to its safety or half-cock position. This construction enables
me to dispense with the herein described shelf groove in the collar q and
the lateral ears upon the trigger block and is in other respects a more
desirable arrangement.

page_text: The Figures in the Drawing which represent this modification are
10, 11, and 12, the former (10) being a perspective view of the two
collars and their rod. The second (11) a section of the same in
combination with the sear, and the latter (12) a perspective view of the
sear.
Figure 14 of the accompanying Drawing shows a construction of a
cartridge case which I propose adopting with my present fire-arm, and
which consists of a metallic shell on whose outer end or base the usual
flange is omitted, the purpose being to enable such shell to be readily
discharged from the breech or breech bolt of the arm in manner as herein
stated.
In order to adapt this arm to the use of such cartridge cases as contain
an annular rim by which to withdraw them from the barrel I construct
the bolt I in two parts, the line of division being preferably immediately
in advance of the handle f.
If a flanged cartridge case is to be used I adopt a plain hook or its
equivalent to seize hold of such flange and by this means the shell, while
if a plain cartridge case is used I adopt an extractor similar to that
referred to above.
The joint between the two portions of the bolt when divided as
last explained consists briefly of a tenon projecting from one and entering
a recess or socket in the other, a projecting arm or lip being formed upon
the tenon to enter an annular channel cut in the socket by which the
endwise connection of the two is ensured. This construction of joint is
shown in Figures 15, 15, 15b, of the accompanying Drawing, in which
a is the movable portion of the bolt I, and 63 the hook attached to it
which extracts the shell, being the tenon and as the socket of the joint,
while the projecting lip above named is shown at e* and the channel to
secure it at f³.
A further modification of this arm which I have contemplated is to
employ in place of the tripper 7 herein shown a plain bar of metal which
lays in a groove or depression formed in the under side of the breech
bolt I, and confined therein by a screw or otherwise, the relative
length of this bar and depression being such that the former is per-
mitted a slight play in the latter longitudinally of the bolt, by which
when it abuts against the stop d¹ it is driven against the cartridge
shell and ejects the latter in manner similar to that effected by the
tripper l.

page_text: I would call especial attention to the important function performed by
the depression or recess in the forward end of the breech bolt, whether
such recess be semicircular or concave, as shown in Figure 1 of the
accompanying Drawing, or a flat recess. By means of this recess and
the device or agent employed with it to extract the cartridge shell I am
enabled to maintain this shell in axial alignment with the bore of the
barrel and of the receiver C, no matter what may be the diameter of the
breech bolt. Without this recess or its equivalent the shell is forced
toward one side of the roadway and binds and sticks therein to such an
extent as to be very objectionable, and it is from this cause that many
arms now in service which use a paper cartridge cannot be converted to
the use of metallic cased cartridges owing to the discrepancy existing
between the diameter of the bore of the arm of the breech bolt.
CLAIM.
SILVANUS FREDERICK VAN CHOATE.
SILVANUS FREDERICK VAN CHOATE.