U.S. patent number 3,776,096 [Application Number 05/191,297] was granted by the patent office on 1973-12-04 for gas operated firearm.
Invention is credited to John S. Donovan.
United States Patent |
3,776,096 |
Donovan |
December 4, 1973 |
GAS OPERATED FIREARM
Abstract
A belt fed, gas fired machine gun has its gas port located just
forward of the firing chamber so that the weight of its associated
cylinder and piston is concentrated towards the rear of the gun.
Power for operating the bolt, firing pin hammer and ammunition feed
is stored in springs opposing movement of the piston in response to
the gas firing pressure. The bolt has longitudinal movement only
and is locked in chambered position by a cam actuated rotary latch
which also performs the triggering function when the gun is
operated in the full automatic setting. Interlinked ammunition is
fed transversely through the gun by reciprocal tray pieces which
are actuated by leaf springs whose return movement is imparted by
return of the bolt to its chambered position. Vertically slidable
sear plates latchably control the firing pin hammer, which is
mounted telescopically within the bolt. The gun is assemblable for
either right or left hand operation.
Inventors: |
Donovan; John S. (Detroit,
MI) |
Family
ID: |
22704917 |
Appl.
No.: |
05/191,297 |
Filed: |
October 21, 1971 |
Current U.S.
Class: |
89/174; 42/75.02;
89/188; 89/35.01; 89/149; 89/192; 89/142 |
Current CPC
Class: |
F41A
19/33 (20130101); F41A 3/26 (20130101); F41A
5/18 (20130101); F41A 35/06 (20130101) |
Current International
Class: |
F41A
19/00 (20060101); F41A 5/00 (20060101); F41A
35/00 (20060101); F41A 19/33 (20060101); F41A
5/18 (20060101); F41A 35/06 (20060101); F41A
3/26 (20060101); F41A 3/00 (20060101); F41d
005/08 () |
Field of
Search: |
;42/69A
;89/174,188,191,192 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bentley; Stephen C.
Claims
I claim:
1. In a gun having a firing chamber, a retractable bolt for closing
said chamber, spring means including a first spring for retracting
the bolt and a second spring for returning the bolt to its chamber
closing position, buffer means movable against both said springs by
the pressure of the gases of explosion, releasable latch mans for
delaying retraction of the bolt pending dissipation of said gas
pressure, and means operative to release said latch means in
response to dissipation of said gas pressure, said last named means
including cam means and a third spring interposed between said cam
means and said buffer means.
2. In the gun of claim 1, said buffer means and bolt being in
telescopic relation with each other, and said first spring means
comprising a coil spring telescopically interposed between the
buffer means and bolt.
3. In the gun of claim 2, a housing slidably supporting the bolt
and buffer means, and spring chambers extending longitudinally of
said housing and enclosing said second and third springs.
4. In the gun of claim 3, said bolt carrying a firing pin and a
hammer movable into striking engagement with the firing pin,
releasable sear means for retaining the hammer during return
movement of the bolt to its chamber closed position, and hammer
spring means for propelling the hammer into striking engagement
with the firing pin upon release of said sear means, said hammer
spring means being connected to the bolt for applying bias thereto
during said return movement of the bolt.
5. In a gun having a retractable bolt, bolt guiding means, said
bolt and guiding means each having a non-circular cross-section
preventing rotation of the bolt in the guiding means, a rotary
latch embracing the bolt and journalled for rotation relative to
the bolt and guiding means, said latch having a non-circular
aperture registerable with said non-circular cross section of the
bolt to accommodate retraction of the bolt therethrough when the
latch is rotated to its bolt releasing position, spring means
interposed between said guiding means and the latch and rotatably
biasing the latch to its bolt retaining position in which said
aperture is out of registry with said bolt cross section, and cam
means operative to rotate the latch to its said bolt releasing
position against the bias of said spring means in response to
firing of the gun.
6. In the gun of claim 5, said non-circular cross section of the
bolt comprising two oppositedly disposed part-circular sections
interconnected by radially extending ribs extending longitudinally
of the bolt, each of said ribs having a transversely extending slot
intermediate the ends thereof, said slots accommodating rotation of
the latch between its bolt retaining and bolt releasing
positions.
7. In a gas fired machine gun having a barrel with a bore and a
firing chamber at the rear end of said bore, a housing supporting
the rear end of said barrel and extending rearwardly therefrom, a
retractable bolt for opening and closing said chamber, said housing
having a bore slidably supporting said bolt and a counter bore
extending rearwardly from said bolt bore, the sidewalls of said
housing having slots extending longitudinally of said counter bore,
generally U-shaped spring chambers secured to the housing opposite
said slots, a generally tubular shaped buffer member slidably
fitting said counter bore and having arms projecting
perpendicularly thereof at its front end, said arms extending
through slots into said spring chambers, a shoulder butt closing
the rear end of said counter bore and spring chambers a cylinder
extending forwardly of one of said chambers, a piston slidably
fitting said cylinder, the rear end of said piston being in
abutment with the buffer member in said one spring chamber, said
barrel having a gas port extending laterally outward from its bore
adjacent the firing chamber, said cylinder having a passage
connecting its forward end with said port, a coil compression
spring in each of said spring chambers, said springs being in
abutment at their forward ends with said buffer member arms, said
spring in said one spring chamber being in abutment at its rear end
with said shoulder butt, a spring retainer slidably mounted in the
other of said spring chambers and abutting the rear end of the
other of said springs, a rotary latch for releasably retaining the
bolt in its chamber closed position, a cam member connected to said
spring retainer, said latch having an actuating finger drivable by
said cam member to release the bolt, said bolt having a nut
slidably fitting the internal walls of the buffer member, external
ribs on the bolt spaced forwardly thereof from said nut, said
buffer member having an internal flange at its front end, said
flange being abuttable with the rear ends of said ribs, and a coil
compression spring surrounding the bolt within the buffer member
and having its opposite ends abutting said flange and nut,
respectively.
8. In a gun having a bore, a firing chamber at the rear end of said
bore, a bolt actuatable to open and close said chamber, and means
for actuating said bolt including a gas port connected to the bore,
a cylinder extending longitudinally of the gun and connected at its
forward end to said port, and a piston operatively connected to the
bolt and movable rearwardly in said cylinder in response to gas
pressure developed at said port upon firing of the gun, spring
means yieldably opposing said rearward movement of the piston, said
spring means including a first spring biasing the bolt to its
chamber open position, a releasable latch engagable with the bolt
to prevent its movement in response to the biasing force of said
first spring pending release of the latch, and cam means actuatable
to release said latch, said spring means including a second spring
for actuating the cam means upon dissipation of said gas pressure,
said second spring having one end movable with the piston and its
other end connected to said cam means.
9. In the gun of claim 8, a buffer member movable with the piston
and having a lost motion connection with the bolt accommodating
rearward movement of the buffer member pending release of the bolt
by said latch, said first spring being operable upon release of the
bolt by the latch means to take up the lost motion of said
connection by actuating the bolt to its chamber open position, said
spring means including a third spring yieldably opposing said
rearward movement of the buffer member and operable to return the
bolt with the buffer member to the chamber closed position of the
bolt.
10. In the gun of claim 9, a housing extending rearwardly of said
chamber and cylinder, a spring finger secured at one end for pivot
movement relative to the housing and having a shoulder intermediate
its ends, said buffer member having a manual operating lever
engagable by said shoulder, and a buffer cocking spring pivotally
biasing the finger against the lever to effect its latching
engagement by said shoulder.
11. In a gun having a barrel with a bore and a firing chamber at
the rear end of said bore, a bolt for closing said chamber, said
bolt being retractable axially of said bore to open said chamber, a
releasable latch for retaining said bolt in its chamber closed
position, a buffer member movable rearwardly relative to the bolt
while the bolt is retained in its chamber closed position by the
latch, spring means yieldably opposing rearward movement of the
buffer member including a first spring reacting against the bolt
and operative to retract the bolt when the latch is released, and
means for moving the buffer member rearwardly against said spring
means in response to the gas pressure developed in the chamber
during firing of the gun, said last named maens including a gas
port in said bore, a cylinder extending longitudinally of the gun
and having its forward end connected to said port, a piston
connected to the buffer member and extending into the rear end of
said cylinder, and a cam member movable to release said latch, said
spring means including a second spring reacting against the cam
member and operative to move the cam member to release the latch in
response to dissipation of said gas pressure.
12. In the gun of claim 11, said buffer member having a lost motion
connection with the bolt accommodating rearward movement of the
buffer member while the bolt is retained in its chamber closed
position, said last motion being taken up during retraction of the
bolt by said first spring when the latch is released, said spring
means including a third spring, fixed reaction means for said third
spring, said third spring being operative to return the bolt with
the buffer member to the chamber closed position of the bolt and
the cam member and piston to their initial positions, and a latch
spring operative to return the latch to its bolt retaining position
when the bolt returns to its chamber closed position.
13. In the gun of claim 12, a firing pin telescopically slidable in
the forward end of the bolt, a hammer telescopically slidable in
the rear end of the bolt, a spring interposed between the hammer
and the rear end of the bolt for biasing the hammer into striking
engagement with the firing pin, said hammer having a rearwardly
extending stem, and sear means for releasably interengaging said
stem during retraction of the bolt.
14. In the gun of claim 12, said sear means including a sear plate
movable in a plane perpendicular to said stem, said sear plate
having an aperture spaced from one end thereof, said stem being
receivable within said aperture and having a forwardly presenting
face engagable with the sear plate at one edge of said aperture, a
sear spring biasing said sear plate perpendicularly of the stem in
the direction to engage said edge with the stem face, means for
disengaging said sear plate edge from said stem face including a
longitudinally shiftable rod extending longitudinally of the gun,
the rear end of said rod being in abutment with said sear plate
end, one of said sear plate end and said rod end having a ramp
surface facing the other.
15. In the gun of claim 14, means for shifting said rod rearwardly
to disengage said sear plate edge from said hammer stem face,
including a trigger depressable toward the forward end of said rod,
said trigger having a rearwardly presenting end face, a shoulder
spaced forwardly of said end face and a bore extending therethrough
adjacent said end face, an actuator having a first leg extending
through said bore and a second leg disposed laterally of said first
leg, said second leg being in abutment with the forward end of said
rod, said actuator being shiftable axially of said trigger bore
between a first position and a second position, said actuator in
said first position having its said second leg abuttable by said
trigger end face whereby said trigger rod is shifted rearwardly by
depression of the trigger, said actuator in said second position
having its said second leg abuttable by said trigger shoulder when
said trigger is depressed, said latch having a finger operable
during movement of the latch to its bolt retaining position to
shift said second leg rearwardly from said trigger shoulder whereby
said rod is shifted rearwardly in response to said latch spring
returning said latch to its bolt retaining position.
16. In the gun of claim 15, means for selectively shifting said
actuator to said first and second positions, including a rotatable
tumbler, a leaf spring having one end disposed opposite the
extended end of said actuator first leg and its other end fixed to
rotate with said tumbler, whereby in response to rotation of said
tumbler in one direction said leaf spring biases the actuator
towards its said second position, and a coil spring interposed in
thrust between said trigger and the extended end of said actuator
first leg, whereby in response to rotation of the tumbler in the
opposite direction said coil spring biases the actuator toward its
said first position.
17. In the gun of claim 15, said trigger having a second shoulder,
said tumbler having an end movable into abuttable relation with
said second shoulder by continued rotation of the tumbler in said
opposite direction after said actuator has shifted to its said
first position, whereby depression of the trigger is blocked by
said tumbler.
18. In a gun having a barrel with a bore and a firing chamber at
the rear end of said bore, a bolt for closing said chamber, said
bolt being retractable axially of said bore to open said chamber, a
releasable latch for retaining said bolt in its chamber closed
position, a buffer member movable rearwardly relative to the bolt
while the bolt is retained in its chamber closed position by the
latch, spring means yieldably opposing rearward movement of the
buffer member including a first spring reacting against the bolt
and operative to retract the bolt when the latch is released, and
means for moving the buffer member rearwardly against said spring
means in response to the gas pressure developed in the chamber
during firing of the gun, said last named means including a gas
port in said bore, a cylinder extending longitudinally of the gun
and having its forward end connected to said port, a piston
connected to the buffer member and extending into the rear end of
said cylinder, said bolt having an externally cylindrical portion
and diametrically opposite ribs extending forwardly of said
portion, said latch having a part-cylindrical bore journalling the
latch on said bolt portion when the bolt is in its chamber closed
position and having diametrically opposite keyways accommodating
passage of the bolt ribs therethrough when the latch is rotated to
its bolt released position, a housing slidably supporting the bolt
and thrustably supporting the latch against rearward movement, a
latch spring rotatably biasing the latch to its bolt retaining
position in which said keyways are out of alignment with the bolt
ribs, said latch having a finger spaced from and extending
transversely of the bolt, and a cam member mounted for rearward
movement to shift said finger transversely of the bolt and thereby
rotate the latch to its bolt released position, said spring means
including a second spring reacting against the cam member and
operative to impart said rearward movement to the cam member when
the thrust force imposed on the latch by the gas pressure against
the bolt during firing of the gun is relieved.
19. In a gun having a barrel, a firing chamber at the rear end of
the barrel, a retractable bolt for closing the chamber, bolt
retracting means operative in response to gas pressure developed in
the barrel during firing of the gun, said retracting means
including a cylinder extending rearwardly of and connected to a
port in the barrel, a piston in the cylinder and spring means
opposing rearward movement of the piston, said spring means being
disposed rearwardly of the piston and operatively connected to the
bolt, releasable latch means for retaining the bolt in its chamber
closed position, cam means actuatable by said spring means upon
dissipation of said gas pressure to release said latch means for
retraction of the bolt by said spring means, buffer means movable
rearwardly with the piston and connecting the piston to said spring
means, said spring means including one spring having fixed reaction
means, said buffer means having lost motion connections with the
cam means and the bolt, said lost motions being taken up by the
actuation of the cam means to release the bolt and the retraction
of the bolt, respectively, said one spring being operable
thereafter to return the buffer means, piston, cam means and bolt
to their initial positions.
20. In the gun of claim 19, a firing pin, a hammer for striking the
firing pin, resilient means interposed between the bolt and hammer
for biasing the hammer into striking engagement with the firing
pin, and releasable sear means retaining the hammer against
movement by said resilient means during return of the bolt to its
chamber closed position, said firing pin and hammer being slidably
carried in opposite ends of the bolt.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to fire arms of the gas fired semi-automatic
and automatic type, and particularly to improved actuating means
therefor. Prior manually held guns of this type have tended to be
of a design in which the gas actuating pressure is taken from a
port in the barrel located a considerable distance forwardly of the
firing chamber, in many cases just rearwardly of the muzzle. As a
consequence, weight of the gas power cylinder lies well forward of
the trigger and the stock or other supporting portion of the gun,
resulting in loss of needed weight concentration to obtain optimum
balance for mitigating firing inertia force. Exemplary of such
prior art arrangements are those disclosed in U.S. Pat. No. 784,966
Smith, 1,010,899 Halle, 1,019,620 Farquhar et al., 1,786,207
Hudson, 2,101,862 MacGregor, 2,386,205 Garand, 2,975,679 Fletcher,
2,981,158 Fletcher and 3,318,192 Miller. The gun of my invention
avoids this problem by having the gas port located just forwardly
of the firing chamber so that the gas cylinder and its piston may
be made relatively short and the weight thereof concentrated closer
to where the gun is supported.
Also, while it is old in the prior art, as for example in the
aforementioned Halle, Farquhar et al. and MacGregor patents, to
employ the gas pressure to build up a spring force to actuate the
bolt, I believe I am the first to utilize a plurality of springs
which initially operate in parallel to absorb the gas pressure
force and thence serve sequentially to actuate the bolt latch,
power the retraction of the bolt, recocking of the hammer and
trigger controlled sear mechanism, the re-chambering of the bolt,
as well as the feeding of ammunition and ejection of spent
cartridges.
Also the bolt is of unique design in that it co-axially mounts the
firing pin and hammer, the hammer having a rearward stem portion
extending beyond the rear end of the bolt for engagement with a
vertically slidable sear which is releasable by a selectively
manually or automatically actuatable rod.
Another unique feature of my gun lies in the bolt latch which
operates rotatably about the longitudinal axis of the bolt and is
cammed to the unlatched position by a member driven by the gas
piston. I also provide a novel ammunition feeding arrangement
wherein a belt of interlinked cartridges is passed horizontally
through the gun by reciprocating members which grip successive belt
links, the reciprocation being imparted by side mounted spring
fingers whose return movement is actuated by the return movement of
the bolt.
The means by which these and other advantages and improvements are
attained will be understood from the following description of a
preferred embodiment selected to best illustrate the invention,
having reference to the drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2 and 3 are left side, right side and top elevational
views, respectively, of a machine gun embodying the invention.
FIG. 4 is a longitudinal vertical section taken substantially along
the line 4--4 of FIG. 3, certain parts being shown in elevation and
only the rear portion of the barrel being illustrated;
FIG. 5 is a longitudinal horizontal section taken substantially
along the line 5--5 of FIG. 1, certain parts being shown in
elevation;
FIGS. 6 and 7 are transverse cross sections taken substantially
along the lines 6--6 and 7--7, respectively, of FIG. 5.
FIG. 8 is a partial horizontal section taken substantially along
the lines of 8--8 of FIG. 4.
FIG. 9 is a perspective view of the ammunition feed upper and lower
spring fingers, shown removed from the assembly.
FIG. 10 is a perspective view of the gas power cylinder and its
integral mounting ring, shown removed from the assembly.
FIG. 11 is a transverse cross section taken substantially along the
line 11--11 of FIG. 4.
FIG. 12 is an end elevational view of the snap ring, shown removed
from the assembly.
FIG. 13 is a side elevational view of the buffer member, shown
removed from the assembly.
FIG. 14 is a horizontal longitudinal section of the buffer member,
taken substantially along the line 14--14 of FIG. 13.
FIG. 15 is a front end elevational view of the buffer member, taken
in the direction of the arrows 15--15 of FIG. 13.
FIG. 16 is a side elevational view of the housing, shown removed
from the assembly.
FIG. 17 is a front elevational view of the housing, taken in the
direction of the arrows 17--17 in FIG. 16.
FIGS. 18, 19 and 20 are transverse sections of the housing, taken
substantially along the lines 18--18, 19--19 and 20--20,
respectively, of FIG. 16.
FIGS. 21, 22 and 23 are perspective views of one of the feed trays,
the buffer locking spring, and the bolt latch, respectively, shown
removed from the assembly.
FIG. 24 is a partial side elevational view of certain interrelated
parts of the triggering mechanism, as viewed from the left side of
the gun, the parts being in their "safety" condition.
FIGS. 25 and 26 are perspective views of the trigger and trigger
rod actuator, respectively, shown removed from the gun.
FIG. 27 is a partial side elevational view similar to FIG. 24, but
showing the parts of the triggering mechanism at the stage of
operation intermediate the depression of the trigger and the
releasing of the bolt latch, the gun being operated in the "full
automatic mode."
FIGS. 28 and 29 are partial elevational views, looking rearwardly
and downwardly of the gun, respectively, showing the parts of the
triggering mechanism under the same condition as in FIG. 27.
FIG. 30 is a view similar to FIG. 29, but showing the relative
position of the parts therein after the bolt latch has moved to its
bolt released position.
FIG. 31 is a view similar to FIG. 24, but showing the parts of the
triggering mechanism with the gun arranged for operation in the
"semi-automatic mode".
FIGS. 32 and 33 are perspective views of the front and rear sear
plates, respectively, shown removed from the gun.
FIGS. 34a, 34b, 34c, and 34d are diagrammatic views showing the
action of the trigger rod and upper and lower sear springs in
controlling the latching and unlatching of the hammer by the front
and rear sear plates during operation of the gun in the
"semi-automatic mode."
FIG. 35 is a partial elevational view of the trigger guard and hand
grip, showing the finger lever in solid lines in its position for
operating the gun in the "full auto-matic mode," and in dashed and
dash-dot lines in its "semi-automatic mode" and "safety" positions,
respectively.
FIG. 36 is a diagrammatic plan view of a portion of the ammunition
belt, with the relative positions of the feed trays indicated in
broken outline.
FIG. 37 is a diagrammatic end elevational view of a portion of the
ammunition belt, taken in the direction of the arrows 37--37 of
FIG. 36, with the relative positions of the feed trays indicated in
broken outline.
DESCRIPTION OF THE PREFERRED EMBODIMENT
General Arrangement
The embodiment of the invention illustrated in the drawings is a
machine gun adapted to be hand held and to fire shells of
approximately 30 caliber, the shells having their cartridges
extending through aligned loops of adjacent cartridge links which
are thus interconnected by the cartridges to form an ammunition
belt which passes through the gun during operation. It should be
appreciated, however, that many of the novel constructional
features of the gun could be applied to the firing of either larger
or smaller bore shells, as well as to so-called automatic guns
having magazine type ammunition feeding arrangements. Also, while
the gun is disclosed as selectively operable either in a "full
automatic mode" (continuous firing while the trigger is maintained
depressed) or in a "semi-automatic mode" (firing one shell with
each successive depression of the trigger), many of its features
could be applied with equal advantage to manually operated bolt
guns of the single shot type.
FIG. 1 shows the external appearance of the gun as viewed from the
left side, with the barrel 1 extending forwardly from the stock
portion, indicated generally by the numeral 2, which terminates
rearwardly in a shoulder butt 3 and intermediate its ends has a
depending trigger guard and hand grip 4.
It should be mentioned at this point that certain hereinafter
described parts associated with the stock portion 2 are reversible
in respect to their orientation in the assembly, enabling the gun
to be alternatively assembled for most convenient operation by
either a "right handed" user or a "left handed" user. Only the
former, or R.H. form of assembly, however, is illustrated in the
drawings. FIG. 1 shows the entrance ends of the upper and lower
feed trays 5 and 6, between which the ammunition belt (not shown)
passes in its horizontal movement transversely through the gun. The
external appearance of the gun as viewed from the opposite, or
right side, is shown in FIG. 2, the exit ends of the ammunition
belt feed trays 5 and 6 being visible therein, as well as the
laterally projecting handle 7 for manually operating the bolt. FIG.
3 shows the external appearance of the gun as viewed from above,
with the barrel 1 extending to the left as in FIG. 1.
Housing and Firing Chamber
Referring now to FIGS. 4 and 5, the main supporting frame for the
stock portion 2 is provided in the form of a housing 8. This
housing extends rearwardly the full length thereof to the butt 3,
and its front end has a forwardly open counter bore 9 into which
the rear portion of the barrel has a close slip fit. The barrel is
retained against the shoulder 10 at the rear end of this counter
bore by a normally expansible snap ring 11 having dual
interengagement with an external groove on the barrel and an
internal groove in the counter bore 9. The bore 12 in the barrel
terminates at its rearward end in a firing chamber 13, in which a
"live" ammunition shell 14 is shown ready for firing.
Power Cylinder and Buffer Member
A short distance forwardly of the firing chamber, the barrel is
provided with an upwardly extending port 15 which connects its bore
12 with a connecting passage 16 leading into the forward end of the
bore 17 of a gas power cylinder 18. This power cylinder extends
rearwardly along the top of the housing 8, being seated thereon in
the upper of two longitudinal grooves provided in the top and
bottom of the housing which are best shown in FIGS. 17, 18 and 19.
Slidably supported in a rear counter bore 19 of the housing for
reciprocation rearwardly of the power cylinder is a generally
tubular shaped buffer member 20. Integral with the forward end of
this buffer member are upwardly and downwardly extending arms 21
and 21' and the laterally extending manual operating handle 7,
which project through respective longitudinal slots provided
therefor in the top, bottom and side walls of the housing rear
counter bore 19. A rod like piston 22 is provided in the bore 17 of
the power cylinder 18 for effecting rearward movement of the buffer
member in response to the gas explosion pressure developed in the
firing chamber 13 when the shell 14 is fired. The rear end of this
piston pilots in a through hole provided in the upper arm 20 of the
buffer member, and the rear end of the power cylinder is counter
bored to receive a flange or collar portion 23 on the piston which
serves both to limit return (i.e., forward) travel of the piston
and to provide a thrust connection between the piston and the
buffer member upper arm 21.
Spring Chambers
The upper and lower arms 21 and 21' of the buffer member are
enclosed in respective upper and lower spring chambers 24, 25 which
extend rearwardly along the top and bottom of the housing 8 to the
butt 3. Within the upper spring chamber 24 and interposed in thrust
between the upper arm 21 and the butt is a coil compression spring
26. Slidably shiftable within the lower spring chamber 25 is a
spring retainer 27 having a rear end wall, and interposed in thrust
between this wall and the lower arm 21' of the buffer member is a
coil compression spring 28. Extending freely through this spring
and slidably piloted in through holes in the buffer member lower
arm 21' and the reatainer end wall is a trigger rod 29. This
trigger rod extends forwardly a short distance beyond the forward
end of the lower spring chamber 25 and terminates within the
trigger guard and hand grip 4. The rear end of the trigger rod, as
best shown in FIG. 8, has a bifurcated or yoke like portion 30 with
laterally spaced arms 31 and 32 extending into the butt 4 and
terminating in downwardly and rearwardly inclined ramp surfaces 33
and 34, respectively.
Bolt
Slidably guided for reciprocation in a bore 35 of the housing,
between the counter bores 9 and 19, is a bolt 36. In its forward or
closed position, as shown in FIGS. 4 and 5, the bolt 36 serves the
conventional functions of chambering the shell 14 and providing the
retention means for the gas pressure force which is released when
the explosive charge in the cartridge 37 of the shell is detonated.
Axial rotation of the bolt in the housing is prevented by upper and
lower ribs 38 and 39 on the bolt which have close sliding
engagement with longitudinally extending upper and lower grooves 40
and 41 in the housing bore 35. The bolt ribs 38 and 39 extend a
short distance forwardly of the main body of the bolt and are
turned inward toward each other to form lugs 42 and 43 for an
interengagement with the usual extraction groove 44 on the rear end
of each shell cartridge. A short distance forwardly of their
rearward end the respective bolt ribs 38 and 39 are interrupted by
grooves or notches 45 and 46, and journalled on the bolt within
these notches is a rotary latch 47. The bolt bore 35 and the rib
receiving upper and lower grooves 40 and 41 are also interrupted
intermediate their ends by a horizontal passageway or slot 48
extending transversely through the housing 8. Adjacent its rearward
end this slot provides clearance for the outer periphery of the
latch 47, and the portion of the slot extending forwardly of the
latch accommodates reciprocation of the upper and lower feed trays
5 and 6. It will be understood that the latch is supported against
axial displacement in the rearward direction by the upper and lower
rear end walls of the slot 48 in the housing, and that the upper
and lower front end walls of this slot and the front face of the
latch cooperate in locating the feed trays longitudinally of the
housing. At its forward end, this slot 48 connects with other
transverse slots, to be later described.
Firing Pin
The bolt 36 has a small axial bore 54 extending through its forward
end for projection of a firing pin 55 to detonate the charge in the
cartridge 37. Extending coaxially and rearwardly of this small bore
is a counter bore 56 in the bolt in which the main body portion of
the firing pin is slidably supported, and in the forward end of
this counter bore is a coil spring 57 for biasing the firing pin
into its normally retracted position, shown. A longitudinal groove
58 in the main body portion of the firing pin cooperates with a pin
59 projecting therein from one side of the bolt to limit the
rearward movement of the firing pin under the biasing force of the
spring 57.
Hammer
Extending coaxially and rearwardly to the rearmost end of the bolt
from the counter bore 56 is a larger counter bore 60 into which the
rear end of the firing pin 55 protrudes, and in which a hammer 61
is slidably supported. The hammer has a rearwardly extending stem
62 which is slidably guided in a central aperture 63 provided in a
nut 64 shown threadably secured to the rear end of the bolt. A coil
compression spring 65 encircles the stem 62 and is interposed in
thrust between the nut 64 and the hammer, so as to bias the hammer
into striking engagement with the rear end of the firing pin. The
stem 62 has an enlarged rear end portion 66 with a rearwardly
facing frusto-conically shaped end face 67, the outer extremities
of which terminate in a forwardly facing shoulder or latching face
68.
Sears
Sear means, in the form of front and rear vertically shiftable sear
plates 69, 70 and upper and lower biasing spring 71, 72, is
provided for latchably interengaging the end portion 66 of the
hammer. When thus latched, the hammer is held in its "cocked"
position shown in FIGS. 4 and 5. The sear springs 71, 72 as
indicated in FIG. 4, may be in the form of single leaf cantilever
springs with their forward ends held fixed to the butt by rivets
73, 74. Both sear plates are biased downwardly by the rearwardly
extending free end of the upper sear spring 71, but the lower sear
spring 72 applies its upward biasing force only against the rear
sear plate 70. Also, both sear plates have central openings therein
to accommodate passage therethrough of the hammer end portion 66,
the upper edge of such opening in the front sear plate and the
lower edge of such opening in the rear sear plate being preferably
chamfered, as indicated at 75 and 76 in FIG. 4, to conform with the
angle of the frusto-conical face 67. The lower end face of the
front sear plate is likewise chamfered, as indicated at 77 in FIG.
4, to conform with the angle of the ramp faces 33 and 34 on the
rearward extremities of the trigger rod 29.
Bolt Retracting Spring
Encircling the portion of the bolt 36 extending into the buffer
member 20 is a coil compression spring 80 which is interposed in
thrust between the nut 64 and an inturned flange 81 on the forward
end of the buffer member. Pending release of the bolt by the rotary
latch 47, this spring 80 thus applies increasing bias tending to
retract the bolt rearwardly from its chamber closed position shown
in FIGS. 4 and 5, as the buffer member is driven rearwardly, from
its position shown, by the piston 22.
Bolt Latch
The latch 47, as best shown in FIG. 23, has a main body portion
with a part circular bore 82 extending axially therethrough, and an
angularly depending leg portion from which a finger 83 extends in
spaced and partially encircling relation about the lower periphery
of the main body portion. The bore 82, which serves to rotatably
pilot the latch on the bolt, is interrupted by diametrically
opposite key ways 84, 85 for accommodating passage of the bolt ribs
therethrough when the latch is rotated into registry therewith. On
the outer periphery of the main body portion of the latch is a
groove 86, one end of which connects with a drilled hole 87
extending through the angularly depending leg portion of the
latch.
Latch Spring
As best seen in FIG. 7, this latch groove 86 and drilled hole 87
serve to recess a generally U-shaped wire spring 88, the upper leg
of which reacts against the upper wall 89 of the housing slot 48
and causes the lower leg to rotatably bias the latch in a clockwise
direction about the bolt 36. Such rotation is limited by the lower
tangentially extending portion 90 of the latch periphery striking
the bottom wall 91 of the housing slot 48, the latch then being in
its "bolt closed" position in which its key ways 84, 85 are out of
alignment with the bolt rib 38, 39 and the latch finger 83 is
approximately centered circumferentially about the underside of the
housing. The latch biasing spring 88, while normally retaining the
latch in such "bolt closed" position shown, will yieldably
accommodate counterclockwise rotation of the latch to its "bolt
released" position in which the key ways 84, 85 are aligned with
the bolt ribs 38, 39. Such counter rotative movement is resisted by
the upper leg of the latch spring becoming further wrapped about
the grooved periphery of the latch body, and is arrested at the
"bolt released" position by the upper tangentially extending
portion 92 of the latch periphery striking the upper wall 89 of the
housing slot 48.
Latch Actuating Cam
A cam member 93 is provided for actuating the latch to its bolt
released position. As best seen in FIG. 8, this comprises a
generally triangular shaped cam nose portion 94 extending
transversely and located mid length of a rod 95. At the opposite
ends of this rod are short arms 96, 96', each with a hook forming
notch 97 facing each other, and equally spaced somewhat fore and
aft of the nose portion 94 are provided a second set of short arms
98, 98'. All four of the arms 96, 96', 98, 98' and the nose portion
94 extend in the same transverse direction, and each thereof, as
well as the rod 95, is arcuate shaped in transverse section to
conform to the curvature of the underside of the housing 8 (FIGS. 6
and 7). The nose portion 94 has oppositely facing lobes 99, 99', of
which only the rearwardly facing lobe 99 is functional in the gun
as assembled for right handed operation. The rearmost arm 96
projects through an elongated slot 100 provided therefor in the
right sidewall of the lower spring chamber 25. Opposite sidewalls
of the spring retainer 26 are provided with apertures 101, 101'
adjacent their forward end, and the notched end of cam member arm
96 extends into the right sidewall aperture 101 of this spring
retainer. The longitudinally extending upper wall 102 of the finger
guard and hand grip 4 supports the forward portion of the cam
member 93, and is arcuate shaped in transverse section (FIG. 6) to
conform to the curvature thereof. In the gun as assembled for right
handed operation, the cam member arm 98 projects through a
longitudinal slot 103, provided in the forward portion of the lower
spring chamber right sidewall, and extends into abuttable
engagement with the front face of the buffer member lower arm 21'.
The cam member 93, including its rod 95, arms 96, 96', 98, 98' and
a portion of the cam nose portion 94, are also visible in FIG.
4.
Feed Spring Fingers
When the bolt 36 is retracted, the upper and lower feed trays 5 and
6 are shifted in a rightward direction, to the broken line position
104 shown in FIG. 5, by upper and lower spring fingers 105, 106.
These fingers, as best shown in FIG. 9, are in the form of spring
metal strips having a slight bow or edgewise curvature between
their front and rear ends. Each has a hole 109 extending
transversely therethrough near its rear end for reception of a
pivot pin 49 which, as shown in FIG. 5, serves both to secure the
finger against longitudinal displacement and to journal it for
vertical pivoting movement. At its front end, each finger has an
arm 110 extending forwardly beyond its main body portion and
defining one side of a forwardly open recess 111 therein. The
oppositely facing edges of their main body portions are also cut
away to form a rearwardly presenting shoulder 112 on each finger,
at a distance somewhat forwardly of midlength thereof. These feed
spring fingers are disposed laterally opposite the flat side face
113 of the housing 8, being retained there-against at their rear
ends by the sidewall 114 of the butt 3 and the rear end of a
longitudinally extending flexible strip 115 which serves as a cover
for the outboard sides of the fingers. Intermediate their ends, as
best shown in FIG. 11, the fingers 105, 106 and their cover strip
115 underlie oppositely disposed arms 116 and 117 projecting from a
lateral extending boss 118 on the bolt and hammer spring retaining
nut 64. Thus, during retraction of the bolt, the arms 116, 117
allow the fingers to swing laterally outward about their rearward
ends; and, during return movement of the bolt, the fingers and
their cover strip are cammed back toward the housing by the arms
116, 117.
Buffer Locking Spring
The laterally projecting bolt nut boss 118 and the manual operating
handle 7 both extend through a horizontal slot in the side of the
housing rear counter bore 19, and each also extends between the
feed spring fingers. Biasing pivotal movement of the fingers into
slidably embracing engagement with the manual operating handle is a
buffer locking spring 119, best shown in FIGS. 7 and 22. This
spring has a vertically extending flat section 120 adapted to abut
against the laterally outward face of the feed spring cover strip.
Its upper and lower ends are reversely bent to form oppositely
facing U-shaped sections 121 and 122, for loosely embracing the
respective upper and lower edges of the cover strip and the feed
spring fingers, and adjacent laterally outward facing U-shaped
sections having their vertically innermost walls 123, 124 extended
for insertion into the respective forwardly open recesses 111 in
the feed spring finger trays. FIG. 7 shows the interrelationship of
the various portions of this buffer locking spring 119 with the
feed spring cover 115 and feed spring fingers 104, 105. As shown
therein, the fingers 104, 105 are in their vertically spread apart
position, forcing the walls 123, 124 of the locking spring into
substantially horizontal planes, since the position of the manual
operating handle 7 is forward of the finger shoulders 112 (FIG. 9).
When the buffer member is moved rearwardly, these fingers remain
thus spread apart until the manual operating handle clears the
shoulders 112, at which point the locking spring 119 draws the
fingers vertically toward each other to position the shoulders 112
in blocking relation with the manual operating handle so as to
arrest return movement of the buffer member.
Manual Operating Handle
This manual operating handle, as best seen in FIGS. 14 and 15, has
a curved forwardly presenting face 125 which is interrupted at its
inboard end by a slot 126 extending vertically thereacross, and by
angled vertically spaced cam faces 127 adjacent its outboard end.
The slot 126 serves to prevent laterally outward swinging movement
of the feed spring fingers during retraction of the bolt until the
bolt ribs 38, 39 strike the buffer member flange 81, moving the
buffer member a further distance rearwardly. Such further rearward
movement of the buffer member disengages the feed spring fingers
from the slot 126 and allows them to swing laterally outward with
retraction of the bolt. Such initial outward swinging movement of
the fingers operates only to shift the blocking interengagement of
the finger shoulders 112 from the slot 126 on the manual operating
handle to the adjacent portion of its forwardly presenting face
125, however, and return movement of the buffer is delayed while
such outward swinging movement of the fingers continues until their
shoulders 112 reach the cam faces 127 on the manual operating
handle. At that point, the buffer member begins rapidly moving
forward under the biasing force of its spring 26, the faces 127
acting to cam the fingers to their vertically spread apart
positions shown in FIG. 7, against the biasing force imposed by the
locking spring 119.
Feed Trays
The upper and lower feed trays 5 and 6 are identical, the upper
being inverted relative to the lower. Each, as best shown in FIG.
21, has a flat rectangular main body portion 128 with front and
rear side flanges partially cut away to provide bolt rib clearance
recesses with oppositely facing shoulders 129, 130. These shoulders
serve as stops engagable by the bolt ribs to limit the stroke of
the trays in their reciprocatory movement transversely of the gun.
The side flanges are also cut back at their receiving ends to
provide inclined ramps 131, which in the case of the lower tray
serve to elevate the ammunition belt (FIG. 37) during operation of
the gun by camming the successive cartridges upwardly to the proper
height for passage between the trays. Lanced out from the main body
portion 128 of each tray is a flexible pawl 132 which drivably
interengages successive links of the ammunition belt during the
ejection and feed stroke, and ratchets over the links during the
return stroke. At its end nearest the stop shoulder 129 the main
body portion 128 of each tray is reversely bent to form a U-shaped
recess 133 extending longitudinally thereacross, for reception of
the forwardly extending arm 110 of its associated feed spring
finger. These recesses 133 have sufficient vertical depth to
accommodate the previously described vertical pivoting movement of
the fingers which accompanies the rearward and return movements of
the buffer member. As shown in FIG. 6, the upper tray 5 is slidably
interposed between the upper rib 38 on the bolt and the upper wall
89 of the housing slot 48, and the lower tray is slidably
interposed between the lower bolt rib 39 and the bottom wall 91 of
this housing slot. During the ejection and feed stroke, which
accompanies the opening or rearward movement of the bolt, both
trays swing laterally outward with the forward ends of the feed
spring fingers, the broken line 134 in FIG. 5 representing the
laterally outward position of the tray at the end of such
stroke.
Power Cylinder Mounting
The gas power cylinder 18, as best shown in FIG. 10, has an
integral mounting ring 140 connected thereto near its forward end
by a depending boss 141. The bore 142 of this ring has a close slip
set on the annular peripheral surface 133 of the barrel 1 and, as
shown in FIGS. 4 and 5, is clamped against a shoulder 144 at the
rear end of this annular surface by a retainer nut 145 threadedly
engaging the barrel. The preassembly of the power cylinder and
barrel is effected before the barrel is inserted into the housing
counter bore 9. Referring to FIGS. 16 and 17, it will be seen that
the housing 8 has a front counter bore 146 for accommodating the
outer periphery of the power cylinder mounting ring 140, and that
the front end of the housing has longitudinally extending cut outs
147, 148 in its upper and lower walls. Each of these cut outs
extends rearwardly through the snap ring groove 149. In the gun as
assembled for right handed operation, the boss 141 extends through
the upper cut out 147.
Barrel Retaining Ring
The snap ring 11, as shwon in FIG. 12, has the inner periphery of
its annular body portion relieved by a series of notches 151 so
that in the event a malfunction in the operation of the gun creates
an undue endwise force against the barrel the remaining inner
peripheral portions 152 of the ring will shear off, allowing the
barrel to shift forward. During installation the ring is slipped
over the barrel 1 and contracted into the barrel groove 149 by
pressing the ring tabs 154 toward each other. When the barrel is
placed in the housing, the tabs are then allowed to swing into
abutment with the sides of the upper cut out 147 in the
housing.
Trigger Guard and Hand Grip Mounting
The trigger guard and hand grip 4 is formed integrally with the
longitudinally extending wall 102 on which the latch actuating cam
member 93 is slidably supported, and is secured by providing the
upper edges of its opposite sidewalls 155, 156 (FIG. 4) with
inturned flanges 157, 158 (FIGS. 6 and 7). These flanges project
into L-shaped grooves 159, 160 (FIGS. 16, 17 and 18) in the bottom
of the housing. Assembly of the trigger guard and hand grip to the
housing is effected by endwise insertion of the flanges into these
housing grooves. A like set of grooves 159' and 160' are provided
in the upper outer wall surface of the housing, but are not used in
the gun as assembled for right handed operation.
Triggering Mechanism
Mounted for longitudinal movement in the trigger guard and hand
grip is a trigger 161, shown in its released or forwardmost
position in FIG. 4. The opposite sidewalls of the trigger guard and
hand grip support a cross shaft 162 with which a generally
trapezoidal shaped tumbler 163 is rotatable in the path of the
trigger, so that when this tumbler is rotated from its position in
FIG. 4 to the so-called "safety" position shown in FIG. 24 the
forward end 164 of the tumbler moves into blocking relation with a
shoulder 165 on the trigger, preventing depression, i.e., rearward
movement, of the trigger. As best shown in FIG. 25, the main body
portion of the trigger is generally in the form of an L-shaped
plate, the rear leg of which is formed with two laterally
projecting bosses having vertical bores 166 and 166' extending
therethrough, and the upper edge of the main body portion between
the bosses is cut away to provide a rearwardly facing shoulder 167
a short distance forwardly of the bores 166, 166'. The left side
bore 166' is not used in the gun as assembled for right handed
operation, but the left bore 166 is used to journal the longer leg
168 (FIG. 26) of a generally J-shaped trigger rod actuator 169.
As shown in FIG. 4, a light coil spring 170 encircles this leg and
serves to bias the actuator downwardly of the trigger, the spring
170 having its upper end abutting the boss on that side of the
trigger and its lower end abutting a retainer clip on the lower end
of the leg 168. Coaxial with the shaft 162 are square section hubs
171, 171', which are formed integral with the tumbler 163 and
extend laterally from opposite sides thereof (FIG. 28), and wrapped
around the left side hub 171 so as to rotate with the tumbler is
one end of a leaf spring 172 whose opposite or free end underlies
the lower end of the actuator leg 168. This leaf spring 172 is
stronger than the light coil spring 170; and, with the trigger and
tumbler in their positions shown in FIG. 4, the actuator is held
upwardly, in abutment with the underside of the bolt latch finger
83, by the leaf spring 172. In this partially elevated position of
the actuator, its shorter leg 173 (FIG. 26) has its lower end
terminating slightly below the upper edge of the rear face 174
(FIG. 25) of the trigger. The trigger rod 29, as shown in FIG. 4,
has its forward end abutting the rear face of the actuator, so that
upon depressing the trigger both the actuator and the trigger rod
move rearwardly with the trigger. Such rearward movement of the
trigger rod causes the ramp surfaces 33, 34 (FIG. 8) at its rear
end to cam the front sear plate 69 upwardly, releasing the hammer
61 to strike the firing pin 55, firing the gun. At the same time,
the rearward movement of the actuator from under the latch finger
83 allows the leaf spring 172 to further elevate the actuator to
the position shown in FIGS. 27, 28 and 29, wherein the shorter leg
173 thereof lies adjacent the rear face of the latch finger. The
actuator then remains in that position, while the trigger is held
depressed, until the latch actuating cam member 93 (FIG. 8) rotates
the latch 47 to its bolt released position. In such bolt released
position of the latch, its latch finger 83 is withdrawn from its
position in front of the actuator, and the front sear plate 69,
under the force of the upper sear spring 71, returns to its lower
position, its ramp face 77 camming the trigger rod forwardly to its
initial position. In so doing, the forward end of the trigger rod
causes the short leg of the actuator to swing forwardly against the
shoulder 167 on the trigger. This latter position of the actuator,
as illustrated in FIG. 30, is in the path taken by the latch finger
83 during its return movement; hence during such return movement
the actuator is swept back to its position shown in FIGS. 27, 28
and 29, and the trigger rod is again shifted rearwardly to effect
refiring of the gun. This triggering action just described takes
place with the gun in its so-called "full automatic mode" of
operation, and continues until the trigger is released, or the
ammunition belt (FIGS. 36 and 37) has passed entirely through the
gun. The tumbler 163 is also rotatably adjustable to an
intermediate position for operation of the gun in the so-called
"semi-automatic mode" in which successive firings each require a
redepression of the trigger. Such position of the tumbler is shown
in FIG. 31, wherein the free end of the leaf spring 172 is
sufficiently lowered to enable the light coil spring 170 to retract
the actuator so that its short leg extends down between the rear
end bosses of the trigger. In such lowered position, the rear face
of the trigger blocks the actuator from rotation in the bore 166,
with the result that the actuator effects rearward movement of the
trigger rod when the trigger is depressed.
Sear Mechanism
The front and rear sear plates 69 and 70 are best shown in FIGS. 32
and 33, and their action in limiting each depression of the trigger
to effect a single firing of the gun in such "semi-automatic mode"
of operation is illustrated diagrammatically in FIGS. 34a through
34d. FIG. 34a represents the condition prior to depression of the
trigger and shows both sear plates held in their lowered position
by the upper spring 71, the hammer latching face 68 being engaged
by the edge 75 of the front sear plate 69, and the trigger rod 29
in its forward position. Upon depression of the trigger, the
trigger rod moves rearwardly against the lower ramp face 77 of the
front sear plate, forcing the front sear plate upwardly to its
position shown in FIG. 34b, and releasing the hammer. Such upward
movement of the front sear plate deflects the upper spring 71
upwardly, allowing the weaker lower spring 72 to elevate the rear
sear plate 70 for latchably engaging the hammer latching face 68
when the hammer 61 (FIGS. 4 and 5) is again driven rearwardly by
the retracting bolt 36 after the gun fires. FIGS. 34c shows the
hammer latching face 68 engaged by the edge 76 of the rear sear
plate, preventing refiring of the gun pending release and
redepression of the trigger. Upon release of the trigger, the upper
spring returns both sear plates to their lower position shown in
FIG. 34d, causing the hammer latching face 68 to be released by the
edge 76 of the rear sear plate and to be again retained by the edge
75 of the front sear plate, and the lower ramp face 77 of the front
sear plate to cam the trigger rod and trigger forwardly to their
original position.
Mode and Safety Lever
Manually operable means for rotatably setting the tumbler 163 in
either the "safety" position (FIG. 24), the "semi-automatic mode"
(FIG. 31) or the "full automatic mode" (FIG. 4), is provided in the
form of a finger lever on the left side of the trigger guard and
hand grip 4 and suitablly keyed to the adjacent end of the shaft
162 with which the tumbler is rotatable. This finger lever 175 is
shown in solid lines in FIG. 35 with its indicating end 176 turned
to the "full automatic mode" setting, and in dashed and dash-dot
lines with it turned to the "semi-automatic mode" and "safety"
settings, respectively.
Ammunition Feed and Ejection
Referring now again to FIGS. 16 and 18, the transverse slot 48 in
the housing opens forwardly into laterally transverse openings 176,
176' whose respective upper and lower walls 177, 178 and 177', 178'
are tangent to the bolt bore 35 and extend forwardly into the
barrel receiving counter bore 9. When the bolt retracts a spent
cartridge from the chamber 13 (FIGS. 4 and 5) after each firing of
the gun, such cartridge is drawn back into the aligned loop of the
ammunition belt link with which it was previously carried into the
housing slot 48, and is then ejected through the right hand end of
slot 48 by the feed trays 5 and 6 as they draw the next live round
into position for chambering by the bolt. The transverse opening
176 in the left side of the housing accommodates passage of the
bullet end of the round into the housing with the feed trays.
FIGS. 36 and 37 illustrate diagrammatically the movement of the
ammunition belt between the upper and lower feed trays 5 and 6
which are indicated in broken line. The belt consists of successive
links, each comprising a pair of axially spaced and aligned loops
179 and 180 which adjacent ends are connected at one side to the
opposite ends of a parallel loop 181. The axially spaced loops 179,
180 of each link loosely embrace the opposite ends of the parallel
loop 181 of the next adjacent link and are retained in axial
alignment therewith by a shell cartridge 37. Each loop 179, 180 and
181 is part circular in transverse section and the opposite sides
thereof form upwardly and downwardly extending ears 182 and 183
which accommodate reciprocation of the bolt ribs therethrough
during chambering and retraction of the cartridges. As best seen in
FIG. 37, the sides 184 and 185 of these ears on each of the axially
spaced loops 179, 180 are engagable by the pawl 132 of the feed
tray, for effecting movement of the cartridge therein into
alignment with the bolt during the feed and ejection stroke
represented by the arrow 186 in FIG. 36. As shown in FIG. 36, the
cartridges extend endwise beyond the remote ends of the loops 179,
180 and have their ends terminating fore and aft of the side
flanges of the trays; whereby during each return stroke of the
trays, represented by the arrow 187, the inclined ramps 131 on the
receiving ends of these flanges of the lower tray 6 cam under the
end of the next succeeding cartridge. This camming action elevates
such next succeeding cartridge to the proper level for passage
between the trays and, in so doing, serves to pull the trailing
portion 188 of the belt upwardly toward the gun in the direction of
the arrow 189 in FIG. 37. During the ejection and feed stroke, the
spent cartridge 190 is carried outwardly of the gun by the same
embracing link loops with which it entered as a "live" shell
14.
Housing and Spring Chamber Subassembly
As best shown in FIG. 11, the upper and lower spring chambers 24
and 25 are of oppositely presenting channel-like shape in
transverse section and their respective sidewalls terminate within
the longitudinal slots 191, 192 in the rear counter bore of the
housing. The outer sidewalls of the spring chambers and the
housing, except the flat side face 113 of the housing, are encased
in a plastic outer shell 193 which extends forwardly from the butt
3 to the external shoulder 194 (FIG. 16) on the housing. This shell
is permanently bonded to the housing and spring chambers and
effects a rigid subassembly of those parts of the gun, and the butt
3 may be secured thereto by suitable manually releasable clip means
(not shown).
Operation
Although the operation of the gun should be clear from the previous
description of the various parts and their interrelation, a brief
review of the principal action which takes place during a complete
firing cycle will now be given, in their order of sequence.
Firing When the trigger 161 is depressed, the trigger rod 29 shifts
rearwardly, elevating the front sear plate 69, and releasing the
hammer latching face 68. The hammer spring 65 thence drives the
hammer 61 forwardly against the firing pin 57, forcing it forwardly
to detonate the live cartridge 37 in the firing chamber 13. The gas
pressure from the resulting explosion is applied through the gas
port 15 into the forward end of the power cylinder 18, driving its
piston 22 and the buffer member 20 rearwardly and compressing the
bolt return spring 26 against the butt 3, the bolt retracting
spring 80 against the nut 64 on the rear end of the bolt 36, and
the cam actuating spring 28 against the rear end wall of the spring
chamber 27. The rearward force on the cam actuating member 93 due
to such compression of its spring 28 is insufficient for the cam
nose portion 94 to cam away the latch finger 83 and thereby rotate
the latch, however, because the latch is frictionally clamped
rearwardly against the housing by the bolt rib with sufficient
force of the gas explosion pressure to restrain rotation of the
latch. The three springs 26, 80 and 28 yield sufficiently to allow
the buffer member to move far enough rearwardly for the feed spring
finger shoulders 112 to latchably engage in the slot 126 on the
front of the manual operating handle 7, the buffer cocking spring
119 pivoting the upper and lower feed spring fingers 105 and 106
vertically toward each other about their rear ends to effect such
latching engagement of the manual operating handle by the shoulders
112.
Bolt Unlocking When the shell 14 leaves the forward end of the
barrel 1, the gas pressure and resultant rearward thrust on the
bolt 36 is sufficiently relieved that the force of the compressed
cam actuating spring 28 is then effective to shift the retainer 27
and cam member 93 rearwardly, causing the cam nose portion 94
engaging the latch finger 83 to rotate the latch to its bolt
released position. The bolt is then retracted by its spring 80.
With the gun operated in the "full automatic mode" (finger lever
175 on the side of the trigger guard and hand grip 4 in its solid
line position shown in FIG. 35), such rotation of the latch also
allows the leaf spring 172 to elevate the trigger rod actuator 169
which, in turn, allows the sear upper spring 71 to move both the
front and rear sear plates 69 and 70 downwardly, the front sear
plate camming the trigger rod 29 forwardly and swinging the short
leg 173 of the trigger rod actuator forwardly against the shoulder
167 on the trigger 161.
Extracting As the bolt retracts, the upper and lower lugs 42 on the
forward ends of its ribs 38, 39, which are engaged with the
extracting groove 44 on the rear end of the spent cartridge,
extract such spent cartridge from the firing chamber back into the
ammunition belt loops it previously occupied. When the rear ends of
the bolt ribs strike the buffer member flange 81 the buffer member
is further retracted sufficiently to allow the feed spring fingers
to swing laterally far enough to shift their shoulders 112 onto the
forwardly presenting face 125 of the manual operating handle 7.
When the rear end of the counter bore 60 in the bolt strikes the
hammer 61, the hammer is driven rearwardly, to be recocked by one
of the sear plates 68, 70. With the gun operated in the
"semi-automatic mode" (finger lever 175 having its indicating end
176 extending forwardly, in the dashed line position shown in FIG.
35), the hammer latching face 68 is initially engaged by the rear
sear plate 70, pending release of the trigger, and subsequently by
the front sear plate when the trigger is released. With the gun
operated in the "full automatic mode," the rear sear plate 70 is
ineffective to cock the hammer because the trigger rod 29 is
automatically released to return to its forward position when the
latch 47 releases the bolt, the latch finger 83 moving out from in
front of the actuator 169 and allowing such return movement of the
trigger rod before the hammer is driven rearwardly by the bolt.
Ejecting and Feeding As the bolt retracts, the arms 116 and 117 on
the bolt spring retainer nut 64 allow the feed spring fingers 105,
106 to swing laterally outward, forcing the feed trays 5 and 6 at
their forward ends to shift the ammunition belt loops 182, 183
containing the spent cartridge toward the right (as viewed in FIG.
5), and bringing the next round in the ammunition belt into
position axially of the firing chamber. When the shoulders 112 on
the feed spring fingers reach the cam faces 127 on the manual
operating handle 7, bolt return spring 26 is enabled to return the
buffer member 20 fully to its forward position, these cam faces 127
wedging the feed spring fingers vertically apart and restressing
the buffer locking spring 119.
Chambering and Locking The forward movement of the buffer member
causes its flange 81 to engage the rear ends of the bolt ribs and
return the bolt to its forward position, chambering the ammunition
round in the chamber 13. Such forward movement of the bolt causes
the arms 116 and 117 on the bolt spring retainer nut 64 to cam the
feed spring fingers back against the flat side 113 in the housing,
forcing the feed trays to shift to the left (as viewed in FIG. 5).
During such return stroke of the trays, the pawls 132 thereof
ratchet over the link loops 182, 183 of the cartridge 37 in the
next succeeding round in the ammunition belt, and the ramp faces
131 on the lower tray 60 cam the second succeeding round upwardly
to the proper height for subsequent advancement toward the gun
during the next ejecting and feed stroke of the trays. During the
forward movement of the buffer member its lower arm 21' engages the
arm 98 on the latch actuating member 93, returning it to its
forward position, determined by the arms 98 and 96 thereof reaching
the forward ends of the slots 103 and 100, respectively, in the
lower spring chamber 25.
Bolt Locking During such forward movement of the latch actuating
cam member its nose portion 94 disengages the finger 83 on the
latch 47, allowing its return spring 88 to rotate the latch back to
its bolt locked position when the notches 45, 46 on the bolt ribs
38, 39 again clear the latch for such rotation. When the gun is
operated in the "full automatic mode," such rotation of the latch
to its bolt locking position causes the latch finger 83 to
rotatably sweep the trigger rod actuator 169 back to its
transversely extending position, shifting the trigger rod 29 to
elevate the front sear and refire the gun.
DISASSEMBLY AND REVERSIBILITY OF PARTS
The gun as described may be disassembled and reassembled for
operation most convenient to a left handed user. Such disassembly
may be initiated by removing the snap ring 11, barrel 1 and the
trigger guard and hand grip 4 from the front portion of the
housing, and separating the butt 3 from the rear end thereof. The
various parts, including the latch actuating cam member 93, latch
47, retainer 27, trigger rod actuator 169, leaf spring 172 and coil
springs 26 and 28 may then be removed. In reassembling the gun for
a left handed user, the barrel and snap ring are installed with the
power cylinder 18 aligned with the spring chamber 25. The latch
actuating cam member 93 is installed, turned end for end, so that
its arm 96' engages in the opening 101' in the retainer 27. This
retainer and cam member, along with the spring 28, are installed in
the spring chamber 24; and the latch 47, with its previously
forwardly presenting face to the rear, is installed on the bolt.
The trigger guard and hand grip 4 is inserted in the housing
grooves 159', 160' the latch finger actuator 169 is inserted in the
bore 166' of the trigger 161 and the leaf spring 172 is installed
on the hub 171' of the tumbler 163. The buffer is installed with
the piston 22 and the trigger rod 29 piloted in the through holes
in the buffer arms 21' and 21, respectively, and the springs 26 and
28 are placed in the spring chambers 25 and 24, respectively.
As thus reassembled the ammunition belt feeds into the right side
of the gun, and the feed spring fingers 105, 106, buffer locking
spring 119 and manual operating lever 7 are located on the left
side for more convenient operation by a left handed user.
Although the invention as described and illustrated in the drawings
represents a preferred embodiment, it is appreciated that various
changes in the parts and their arrangement may be made without
departing from the spirit and scope of the invention as set forth
in the following claims.
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