U.S. patent number 3,566,744 [Application Number 04/854,005] was granted by the patent office on 1971-03-02 for automatic gun receiver combination.
Invention is credited to Eugene M. Stoner.
United States Patent |
3,566,744 |
Stoner |
March 2, 1971 |
AUTOMATIC GUN RECEIVER COMBINATION
Abstract
The automatic gun receiver combination includes a recoiling
barrel, bolt and bolt carrier, two ammunition feeding means, recoil
assembly and buffer assembly. The recoiling barrel reciprocates
axially in the receiver forwardly of the ammunition feeding means.
A bolt is reciprocated axially past the feeding means by a
recoiling bolt carrier. The bolt is also rotated into and out of a
position in which it is locked to the barrel. Two cams extend along
the length of the bolt carrier to cooperate with cam followers on
each of the two ammunition feeding means, either of which may be
selected to feed ammunition into the receiver. The recoil assembly
is coupled between the barrel and receiver both for buffering
recoil and counterrecoil of the barrel and for accelerating the
bolt carrier in recoil relative to the barrel. The buffer assembly
at the rear of the receiver both buffers the recoil force of the
bolt and bolt carrier and mounts a sear, selectively engageable
with the bolt carrier, such that when the sear and bolt carrier are
engaged, the resulting interruption of the counterrecoil of the
bolt and bolt carrier is buffered.
Inventors: |
Stoner; Eugene M. (Port
Clinton, OH) |
Family
ID: |
27050378 |
Appl.
No.: |
04/854,005 |
Filed: |
July 14, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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763449 |
Jul 22, 1968 |
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491300 |
Sep 29, 1965 |
3455204 |
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Current U.S.
Class: |
89/125; 42/25;
89/1.4; 89/132; 89/135; 89/172; 89/199 |
Current CPC
Class: |
F41G
1/46 (20130101); F41A 9/37 (20130101); F41A
19/33 (20130101); F41G 1/28 (20130101); F41A
3/78 (20130101); F41A 5/08 (20130101); F41A
19/64 (20130101); F41A 5/02 (20130101); F41A
19/59 (20130101) |
Current International
Class: |
F41A
19/00 (20060101); F41A 3/78 (20060101); F41A
9/37 (20060101); F41A 5/00 (20060101); F41A
19/59 (20060101); F41A 19/64 (20060101); F41A
5/08 (20060101); F41A 19/33 (20060101); F41G
1/00 (20060101); F41G 1/46 (20060101); F41G
1/28 (20060101); F41A 9/00 (20060101); F41A
5/02 (20060101); F41A 3/00 (20060101); F41d
005/02 (); F41d 011/12 () |
Field of
Search: |
;89/1.4,33--33.25,125,128--135,140--143,160,162,164,169,172,174,177--178
;42/2,14,16,17,18,18.3,19,25,25.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Benjamin A.
Assistant Examiner: Bentley; Stephen C.
Parent Case Text
RELATED APPLICATION
This is a continuation of application Ser. No. 763,449 filed Jul.
22, 1968, now abandoned which was a division of application Ser.
No. 491,300 filed Sept. 29, 1965, now U.S. Pat. No. 3,455,204.
Claims
I claim:
1. An automatic gun comprising, in combination:
a. a receiver having an ammunition feeding station therein;
b. a barrel mounted for reciprocal axial movement in said receiver
forward of the ammunition feeding station;
c. a bolt disposed in axial alignment with the barrel;
d. a bolt carrier adapted to reciprocate longitudinally in said
receiver past the feeding station, the bolt carrier having a
relatively short portion in line with the bolt and connected
thereto and a relatively long portion offset from the bolt, the
length of the longer portion exceeding the stroke of the bolt
carrier;
e. a cam extending along the length of the bolt carrier longer
portion;
f. ammunition-feeding means attached to the receiver, having a cam
follower which cooperates with the cam on the bolt carrier for
feeding ammunition to the feeding station;
g. recoil means disposed alongside the barrel and operably coupled
between the barrel and the receiver for buffering recoil and
counterrecoil forces, said recoil means including an accelerator
disposed forward of and in alignment with the bolt carrier longer
portion and responsive to barrel recoil for engaging the forward
end of the bolt carrier longer portion to accelerate the bolt
carrier in recoil relative to the barrel; and
h. a buffer assembly mounted at the rear of the receiver in
alignment with the bolt, and engageable with the rear of the bolt
carrier upper portion for buffering the recoil force of the bolt
and bolt carrier.
2. An automatic gun in accordance with claim 1 wherein an elongate
operating spring extends through the bolt carrier longer portion
and is operably connected between a forward part of the bolt
carrier longer portion and the rear of the receiver for urging said
bolt carrier forward to the battery position.
3. An automatic gun in accordance with claim 2 including a charging
system comprising:
a. a block mounted for axial movement within the receiver, said
block being disposed forward of the bolt carrier longer portion and
in line therewith;
b. means affixed to the block and extending from the block through
the bolt carrier longer portion to the rear of the receiver for
moving the block rearwardly to engage the forward end of the bolt
carrier longer portion and move the bolt carrier to the rear of the
receiver; and
c. a charger return spring extending through the bolt carrier
longer portion, and operably connected between the rear of the
receiver and the block for returning the block to its forward
position.
4. An automatic gun in accordance with claim 1 wherein said
ammunition-feeding means includes:
a. a feed pawl carrier disposed beside the bolt carrier longer
portion at the feeding station, said feed pawl carrier being
mounted for reciprocation on the receiver;
b. feed pawls protruding on the outboard side of the feed pawl
carrier for engaging rounds of ammunition to feed them to the
feeding station; and
c. means mounting the cam follower on the inboard side of the feed
pawl carrier to reciprocate the feed pawl carrier responsive to
longitudinal reciprocation of the bolt carrier.
5. An automatic gun comprising, in combination:
a. a receiver having an ammunition-feeding station therein;
b. a barrel mounted for reciprocal axial movement in said receiver
forward of the ammunition feeding station;
c. a bolt disposed in axial alignment with the barrel;
d. a bolt carrier adapted to reciprocate longitudinally in said
receiver past the feeding station, the bolt carrier having a
relatively short portion in line with the bolt and connected
thereto and a relatively long portion offset from the bolt and
barrel, the length of the longer portion exceeding the stroke of
the bolt carrier;
e. a pair of cams on opposite sides of the bolt carrier, each
extending along the length of the bolt carrier longer portion;
f. ammunition-feeding means attached to the receiver and comprising
a pair of ammunition guide trays disposed on opposite sides of the
bolt carrier longer portion, an ammunition feed pawl means
associated with each of the ammunition guide trays, each feed pawl
means being engageable with rounds of ammunition in the associated
guide trays to feed ammunition therethrough to the
ammunition-feeding station, a pair of cam follower means each
connected to one of the feed pawl means and cooperable with a
respective one of the cams on the bolt carrier to operate the
ammunition feed pawl means, and means for selectively feeding
ammunition from either of the ammunition guide trays;
g. recoil means disposed alongside the barrel and operably coupled
between the barrel and the receiver for buffering recoil and
counterrecoil forces, said recoil means including an accelerator
disposed forward of and in alignment with the bolt carrier longer
portion and responsive to barrel recoil for engaging the forward
end of the bolt carrier longer portion to accelerate the bolt
carrier in recoil relative to the barrel; and
h. a buffer assembly mounted at the rear of the receiver in
alignment with the bolt, and engageable with the rear of the bolt
carrier shorter portion for buffering the recoil force of the bolt
and bolt carrier.
6. An automatic gun comprising, in combination:
a. a receiver having an ammunition-feeding station therein;
b. a barrel mounted for reciprocal axial movement in said receiver
forward of the ammunition feeding station;
c. a bolt carrier adapted to reciprocate longitudinally in said
receiver past the feeding station, the bolt carrier having a
relatively short sleeve portion adapted to engage the barrel at the
forward end of the bolt carrier stroke, and a relatively long body
portion offset from the sleeve portion, said body portion having a
sear notch near its rear end and a cam extending along its
length;
d. a bolt carried by said sleeve portion;
e. ammunition-feeding means attached to the receiver, having a cam
follower which cooperates with the cam on the bolt carrier to feed
ammunition to the feeding station;
f. recoil means disposed alongside the barrel and operably coupled
between the barrel and the receiver for buffering recoil and
counterrecoil forces of the barrel, said recoil means including
accelerator means disposed forward of and in alignment with the
bolt carrier body portion responsive to barrel recoil for engaging
the forward end of the bolt carrier body portion to accelerate the
bolt carrier in recoil relative to the barrel;
g. a buffer assembly mounted at the rear of the receiver and
engageable with the rear of the bolt carrier sleeve portion for
buffering the recoil force of the bolt and bolt carrier; and
h. a sear assembly at the rear of the receiver, selectively
engageable with said sear notch on the bolt carrier body to
interrupt the forward stroke of the bolt carrier.
7. An automatic gun in accordance with claim 6 wherein:
a. said sear assembly is operably connected to the rear mounted
recoil buffer assembly; and
b. said buffer assembly includes spring means aligned with the
bolt, said spring means being compressible rearwardly for buffering
the recoil force of the bolt and bolt carrier, and compressible
forwardly for buffering sear forces resulting from interrupting the
counterrecoil of the bolt and bolt carrier.
8. An automatic gun in accordance with claim 6 wherein:
a. the barrel has locking lugs at its rear end;
b. the bolt is mounted for axial and rotative movement in the bolt
carrier sleeve portion, and includes locking lugs which pass
between the lugs on the barrel when the bolt is in an aligned
position and cooperate with the barrel lugs for locking the bolt in
battery when the bolt is axially rotated to a locking position;
and
c. a cam slot in the bolt carrier sleeve portion and a cam follower
on the bolt cooperate to rotate the bolt to the aligned position
responsive to rearward movement of the bolt carrier relative to the
bolt, and to the locking position responsive to relative forward
movement of the bolt carrier, said cam slot having a forward and a
rearward portion each parallel to the bolt axis, the forward and
rearward portions being joined by a central portion oblique to the
bolt axis so that the bolt moves axially a limited distance
relative to the bolt carrier when the bolt cam follower is in the
forward and rearward cam slot portions, and rotates relative to the
sleeve portion when the cam follower passes through the central
portion of the cam slot.
9. An automatic gun in accordance with claim 8 wherein:
a. a crevice pin is mounted for radial movement in the bolt carrier
sleeve portion and engageable in a notch in the bolt to fix the
bolt in the forward position relative to the bolt carrier;
b. an elongate cam within the receiver extends alongside the
reciprocal path of the bolt carrier sleeve portion; and
c. a cam follower on the crevice pin cooperates with the elongate
cam to hold the crevice pin engaged when the bolt is out of
battery.
10. An automatic gun in accordance with claim 6 wherein an ejection
pin extends through the bolt and bolt carrier sleeve portion and is
mounted for axial movement therein for ejecting a cartridge case
from the bolt, the rear end of said ejecting pin protruding from
the rear of the bolt carrier sleeve portion for engaging the rear
recoil buffer assembly during recoil of the bolt carrier, thereby
buffering ejection of the cartridge case.
11. An automatic gun comprising, in combination:
a. a receiver having an ammunition feeding station therein;
b. a barrel mounted for reciprocal axial movement in the receiver
forward of the ammunition feeding station;
c. a buffer assembly mounted in the receiver in alignment with the
barrel and rearward of the ammunition feeding station;
d. a bolt disposed in the receiver in axial alignment with the
barrel;
e. a bolt carrier adapted to reciprocate longitudinally in the
receiver and being connected to the bolt for reciprocating the bolt
past the ammunition feeding station, the bolt carrier having:
a relatively short portion in line with the barrel engageable with
the buffer assembly for buffering for the recoil force of the bolt
and bolt carrier;
a relatively long portion offset from the barrel and exceeding the
stroke of the bolt carrier in length, the front part of the offset
portion extending alongside the barrel when the bolt carrier is at
the forward end of its reciprocation and the rear part of the
offset portion extending alongside the buffer assembly when the
bolt carrier is at the rear end of its reciprocation; and
a cam extending along the length of the bolt carrier offset
portion;
f. ammunition-feeding means attached to the receiver having a cam
follower which cooperates with the cam on the bolt carrier for
feeding ammunition to the feeding station; and
g. recoil means disposed alongside the barrel and forward of the
bolt carrier, operably coupled between the barrel and the receiver
for buffering recoil and counterrecoil forces, said recoil means
including an accelerator aligned with the bolt carrier offset
portion and responsive to barrel recoil for engaging the forward
end of the bolt carrier offset portion to accelerate the bolt
carrier in recoil relative to the barrel.
Description
This invention relates to automatic guns, and more particular, to
rapid-firing, short recoil-operated, automatic guns.
In order to be suitable for field use, particularly as a military
weapon, a rapid-firing automatic gun not only must fire
satisfactorily, but also should be easy to repair and maintain in
the field with a minimum of tools. Toward this end, the gun should
be as simply constructed and have as few parts as is consistent
with a high standard of performance.
Further, guns designed to be mounted on military vehicles, e.g.
armored cars, should be relatively compact and light as compared
with stationary guns. The size of that portion of the gun from the
ammunition-feeding tray or magazine rearward is particularly
critical because the rear end of the gun, including usually the
ammunition-feeding tray as well, extends within the cupola of the
armored car. Since the gun is traversed to aim it, the space which
must be allowed for the gun inside the vehicle increases rapidly
with the distance from the tray rearward.
The gun which comprises this invention can be field-stripped easily
and quickly by one man without tools. Many of the parts of the gun
serve multiple functions so that the weight, size and complexity of
the gun is reduced, maintenance is facilitated, and reliability
increased. The parts are arranged to minimize particularly the size
of the gun portion which must be contained within a vehicle.
Generally, in accordance with this invention, the automatic gun is
recoil-operated. The gun barrel reciprocates axially in a receiver
forward of an ammunition-feeding station in the receiver. A bolt is
reciprocated axially past the feeding station by a bolt carrier
which has a relatively short upper portion and a lower portion
which is longer than the bolt carrier stroke. A cam follower on an
ammunition-feeding means cooperates with a cam extending along the
length of the bolt carrier lower portion to feed ammunition to the
feeding station.
A recoil assembly, which is disposed beneath the barrel and forward
of the bolt carrier, is operably coupled between the barrel and
receiver for buffering recoil and counterrecoil forces. Further,
the recoil assembly is responsive to barrel recoil for engaging the
forward end of the bolt carrier lower portion to accelerate the
bolt carrier in recoil relative to the barrel. A buffer assembly at
the rear of the receiver engages the rear of the bolt carrier upper
portion to buffer and recoil force of the bolt and bolt
carrier.
In an exemplary embodiment of this invention, a sear assembly at
the rear of the receiver, which is selectively engageable with a
sear notch on the bolt carrier body to interrupt the forward stroke
of the bolt carrier is buffered by the same buffer assembly as
buffers the recoil force of the bolt and bolt carrier.
This invention also includes several novel subcombinations which,
while particularly useful in the gun combination described above,
are also useful in other automatic rapid-firing guns. For example,
in accordance with one aspect of the invention, the recoil means
includes a fluid cylinder fixed to the receiver and located below
the barrel in alignment with the lower portion of the bolt means.
The internal walls of the cylinder define a large diameter forward
portion in which a recoil piston reciprocates, and a smaller
diameter rearward portion in which an accelerator piston
reciprocates. The recoil piston is fixed to the barrel, and the
accelerator engages the forward end of the bolt carrier lower
portion to accelerate it in recoil relative to the barrel.
The accelerator piston bottoms out after the barrel has completed
an initial part of its recoil movement, and a restricted bypass
opening permits the recoil piston to continue forward a short
distance, buffering the barrel recoil force.
This invention further includes a selective ammunition-feeding
system particularly useful with the gun described above, but also
useful with other guns. Prior art automatic guns commonly used by
the military have used a single store of ammunition for feeding the
gun. Since different types of targets require different types of
ammunition, e.g. high explosive ammunition for personnel, and
armor-piercing ammunition for armored vehicles, such prior art guns
have created problems. Often such prior art guns used a single type
of ammunition which was a comprise between the types desired, or
was designed to be effective against only a limited type of target.
Other times, plural types of ammunition were mixed on a single feed
belt so that all types of ammunition were fired at all targets. It
is evident that neither of these situations was satisfactory.
The selective feeding feature of this invention permits rapid
selection of the proper type of ammunition for each target, thus
increasing the flexibility of the gun and eliminating wasteful
firing of ineffective rounds. Generally in accordance with this
aspect of the invention, the ammunition feed means is coupled to
rounds of ammunition from a plurality of different stores, and
includes selector means for selecting any one of the ammunition
stores to supply ammunition to the receiver.
In an exemplary embodiment, the bolt means which reciprocates
longitudinally in the receiver past the feeding station has a
relatively short upper portion and a relatively long lower portion,
the length of the lower portion exceeding the stroke of the bolt
means. An elongate cam slot is formed in each of two opposite sides
of the lower portion of the bolt means. The ammunition-feeding
means has a pair of cam followers each of which cooperates with a
respective one of the cam slots to operate an ammunition feed pawl
means. Each ammunition feed pawl means is effective to feed
ammunition from a different store, and the selector means are
operative to alternatively select either of the ammunition
stores.
As the optimum ballistic characteristics for each type of
ammunition often differ, the ballistic characteristics of the
ammunition in each of the plural stores will often be different. In
yet another aspect, this invention takes these differing
characteristics into consideration by providing a gun sight means
which is automatically adjusted responsive to the store
selected.
These and other objects and features of this invention will be
apparent from the following description when read with reference to
the accompanying drawings in which:
FIG. 1 is a perspective view showing the preferred embodiment of a
gun constructed in accordance with this invention;
FIG. 2 is an enlarged sectional view taken generally along lines
2-2 of FIG. 1;
FIGS. 3a and 3b are fragmentary, enlarged side views, in section,
showing portions of the recoil assembly illustrated in FIG. 2;
FIG. 4 is a sectional view taken generally along lines 4-4 of FIG.
3a;
FIG. 5 is a perspective view showing a part of the recoil assembly
removed from the gun;
FIG. 6 is a sectional view taken generally along lines 6-6 of FIG.
2;
FIGS. 7--9 are fragmentary, enlarged side views, in section,
showing the central portion of the gun illustrated in FIG. 1 in
successive stages of the firing cycle;
FIG. 10 is an enlarged sectional view taken generally along lines
10-10 of FIG. 2;
FIG. 11 is an enlarged sectional view taken generally along lines
11-11 of FIG. 2;
FIG. 12 is an enlarged sectional view taken generally along lines
12-12 of FIG. 2;
FIGS. 13--16 are fragmentary, enlarged side views, in section,
showing the rear portion of the gun illustrated in FIG. 1 in
successive stages of the firing cycle;
FIG. 17 is an enlarged, rear elevation view of the gun illustrated
in FIG. 1 with portions cut away;
FIG. 18 is a sectional view taken generally along lines 18-18 of
FIG. 15;
FIG. 19 is a perspective view of the rear buffer and sear assembly
removed from the gun;
FIGS. 20 and 21 are fragmentary, enlarged top views, in section,
showing the central portion of the gun illustrated in FIG. 1, and
particularly illustrating the ammunition-feeding means in
successive stages of the firing cycle;
FIG. 22 is a sectional view taken generally along lines 22-22 of
FIG. 20;
FIG. 23 is a sectional view taken along the same lines as FIG. 22,
but showing the bolt and bolt carrier in the forward position;
FIG. 24 is a perspective view of a portion of an ammunition belt
removed from the gun;
FIG. 25 is a fragmentary, perspective view of the ammunition
feeding means with portions cut away;
FIG. 26 is a perspective view of a portion of the ammunition
feeding means removed from the gun;
FIG. 27 is a fragmentary perspective view, in vertical,
longitudinal section, showing the central portion of the gun in the
counterrecoil part of the cycle;
FIG. 28 is a fragmentary top view, in section, similar to FIGS. 21
and 22, but showing the ammunition feed selector in an intermediate
position;
FIG. 29 is a side view, in section, showing an alternative
embodiment of the recoil assembly; and,
FIG. 30 is a diagram of a circuit for selecting a fully automatic
or semiautomatic firing cycle responsive to the ammunition feed
selector.
Referring to FIGS. 1, 2 and 6, an automatic gun is shown, including
a barrel 5, a receiver 6, and ammunition-feeding means 7. The gun
is mounted, e.g. on a vehicle such as a military armored car, by an
exemplary means which includes a collar 11 having internal rails 12
which fit into conforming external grooves 13 on the side of the
receiver. A removable pin 14 extends through aligned apertures 15,
16 in the collar and receiver 6 to fix the gun longitudinally with
respect to the collar. The collar 11 is supported on a horizontal
pivot pin 18 in a yoke 17. A vertical pin 19 extends from the base
of the yoke for mounting the same on a vehicle (not shown) for
pivotal movement about a vertical axis. Thus, the gun is positively
fixed against sliding movement relative to the vehicle, but may be
pivoted to aim the gun.
The barrel is mounted for reciprocal movement along the axis 26 of
its bore in the forward portion of an elongate, generally
cylindrical, upper part 25 of the receiver. A bolt means is
provided for chambering, firing and ejecting rounds of ammunition
27. The bolt means includes a bolt 28, which is aligned with the
barrel axis, and a bolt carrier 29 which is attached to the bolt
and reciprocates longitudinally in the receiver past an
ammunition-feeding station 30 located rearward of the barrel. The
bolt carrier 29 has a relatively short upper sleeve portion 31
which carries the bolt, and a relative long, lower body portion 32
which is housed in a lower, generally rectangular, part 33 of the
receiver.
A recoil assembly 36 located beneath the barrel is operably coupled
between the barrel and the forward end of the receiver lower part
33 for buffering recoil and counterrecoil forces. The recoil
assembly is aligned with the body 32 of the bolt carrier and
engages its forward end to accelerate the bolt carrier 29 in recoil
relative to the barrel.
The recoil force of the bolt 28 and carrier 29 is buffered by a
buffer assembly 38 at the rear of the receiver which engages the
rear of the bolt carrier sleeve 31 near the end of the recoil
stroke. A sear 41 pivotally connected to the buffer assembly 38
engages in a sear notch 42 on the bolt carrier body 32 to interrupt
counterrecoil movement of the bolt and bolt carrier and retain them
in the rearward cocked position. Depression of a trigger mechanism
40 raises the sear 41 out of engagement with the notch 42 to fire
the gun.
A muzzle break 43 is connected on the forward end of the barrel to
permit gas to escape rearwardly through openings in the break.
Referring now to FIGS. 6 and 9, as well as to FIG. 2, a breech
barrel extension 48 is threaded onto the rear of the main barrel
portion. The external surface of the barrel extension forms a
bearing surface which slideably engages an internal bearing surface
49 in the upper forward portion 25 of the receiver. A collar 50
affixed around the barrel also has an external bearing surface 51
which slideably engages a corresponding internal bearing surface 52
in the forward end of the upper forward receiver portion 25 to
support the barrel. A shoulder 53 at the forward end of the barrel
collar 50 abuts a shoulder 54 intermediate the ends of the barrel,
and a nut 55 threaded onto the barrel forward of the collar holds
the collar in place longitudinally. Tabs 56 on a lock washer 57
between the nut 55 and the collar 50 are bent in opposite
directions into detents on the collar and nut to retain the nut 55
against accidental loosening. The collar is fixed against rotation
relative to the barrel by an internal longitudinal key 60 on the
collar which is inserted in a corresponding keyway 61 formed in the
barrel. A lug 62 which depends downwardly from the collar, extends
through a forwardly open guide slot 63 in the receiver, and engages
the sides of the guide slot to fix the collar 50 and barrel against
rotation relative to the receiver, while permitting axial
reciprocation.
Referring particularly to FIGS. 2, 3a and 3b, the recoil assembly
36 includes a recoil cylinder 70 the forward end of which extends
through an ear 71 depending from the receiver 6 and the rear end 72
of which is threaded into the front of the receiver lower part 33,
so that the cylinder extends parallel to and below the barrel axis
26 in alignment with the bolt carrier body 32. The recoil cylinder
70 houses a recoil piston 73 which has a piston head 75 and piston
rod 74 extending forward from the head and on through an aperture
76 in the depending portion of the barrel collar lug 62. A sleeve
nut 77, threaded onto the piston rod 74 has an external flange 78
which abuts the barrel collar lug 62 to retain it on the piston
rod. Accidental loosening of the sleeve nut 77 is prevented by a
spring biased plunger 79 which engages in any of a plurality of
detents 80 formed around the flange 78 of the nut. An adjusting nut
83 on the piston rod rearward of the collar lug 62 accurately
locates the longitudinal position of the barrel relative to the
receiver and recoil mechanism. An arcuate piece of resilient
material 85 is wedged into a tapered arcuate slot 86 in the
adjusting nut to hold it at any selected place of adjustment along
the threads 87 of the piston rod.
The sleeve nut is knurled on its external surface so as to
facilitate its removal by hand. With the sleeve nut 77 removed, the
barrel may be freely slid out the forward end of the receiver.
Because the recoil piston rod 74 is fixed to the barrel 5 by the
sleeve nut 77 and adjusting nut 83, the recoil piston head 75
reciprocates rearwardly and forwardly with the barrel in recoil and
counterrecoil, respectively.
The recoil piston head reciprocates in a front bore 91 of
relatively large internal diameter in the recoil cylinder 70, and
an accelerator piston 93 reciprocates in a rear bore 92 of smaller
internal diameter in the cylinder. The accelerator piston 93
includes a piston head 95 sealed by an O-ring seal 96. The interior
of the recoil cylinder, between the recoil piston head 75 and the
accelerator piston head 95, is filled with hydraulic fluid so that
as the recoil piston moves rearwardly in recoil, the smaller
diameter accelerator piston 93 is driven rearwardly at an increased
velocity.
The accelerator piston 93 is hollow. It has a closed forward
extension 101 protruding forward from the piston head 95 and also
has an open rear extension 107 which protrudes rearwardly from the
piston head 95. In recoil, the rear extension 107 of the
accelerator piston engages the aligned forward end 97 of the bolt
carrier body 32 to push the bolt carrier 29 rearward from the
battery position illustrated in FIG. 2. Rearward movement of the
accelerator piston is limited by an interior shoulder 108 at the
rear end of the recoil cylinder.
A heavy recoil spring 98 interior of the recoil cylinder is
compressed between a shoulder 99 in the cylinder wall and the
recoil piston head to urge the recoil piston 73 forward. The
accelerator piston 93 is urged forward by a lighter return spring
100, which is housed in the hollow accelerator piston and the
closed forward extension 101 thereof nested within the recoil
spring 98. The accelerator spring 100 is compressed between the
closed forward end of the accelerator piston and a plug 102. The
plug 102 is slideably mounted within the rear extension 107 of the
accelerator piston and abuts a stop pin 103 which is fixed to the
recoil cylinder 70 and extends through an elongate slot 104 in the
rear extension of the accelerator piston. In its forward position,
the accelerator piston head 95 abuts an annular ring 105 interposed
between the shoulder 99 and the recoil spring 98. Since the recoil
spring is considerably stronger than the accelerator spring, this
limits forward movement of the accelerator piston.
A wedge-shaped, or tapered, throttling groove 110 (FIGS. 3a and 4)
is formed in the wall of the large diameter part of the recoil
cylinder. The throttling groove 110 permits a programmed amount of
fluid to bypass the recoil piston head after the recoil piston head
has moved a selected distance rearward in recoil. An annular spacer
111 (FIGS. 3a and 5) having forwardly extending spaced-apart
fingers 112 is interposed between the forward end of the recoil
spring and the recoil piston head to provide radial passageways
113, assuring that fluid communication between the throttling
groove 110 and the fluid in the chamber portion rearward of the
piston head 75 is not blocked off by compression of the recoil
spring 98. Sealing of the bypass 110 is a particular problem
because the high acceleration encountered in rapid firing automatic
guns causes the recoil spring to compress dynamically, with the
greatest amount of compression in the forward portion adjacent the
recoil piston head at the initial stages of recoil.
The chamber within the recoil cylinder 70 is sealed at the rear end
by the accelerator piston head seal 96. At the forward end, the
chamber is effectively terminated by a threaded plug 115 through
which the recoil piston rod 74 extends in engagement with an O-ring
seal 114. The recoil piston head 75 divides the chamber within the
recoil cylinder into a rear chamber and a forward chamber. The
recoil piston head is approximately the same diameter as is the
forward bore 91, but there is no seal between the piston head and
bore. Air may be bled from the cylinder chamber by backing off a
set screw 116 to unseat a ball valve 117 in the plug 115.
A bellows-type cover 118 extends between the plug 115 and the
adjusting nut 83 to enclose the extended sealing surface of the
recoil piston rod 74.
The recoil piston head 75 has a check valve 122 formed thereon to
facilitate the return of the barrel to battery position in time to
receive the next round. The check valve 122 opens on forward
movement of the recoil piston to permit fluid to flow rearwardly
through a plurality of small orifices 123 in the recoil piston
head. The vale valve 122 includes an annular flapper ring 124 which
is seated by a spring 125 compressed against an outwardly extending
shoulder or cap 126 fixed on a central rear extension 128 on the
recoil piston head, to seal the orifices 123 except during forward
movement of the piston head.
Belville or cup counterrecoil springs 127 stacked in
series-parallel forward of the recoil piston head cooperate with
the piston head and the plug 115 to buffer counterrecoil forces.
The recoil piston rod 74 is hollow to provide a reservoir for
replenishing hydraulic fluid in the chamber of the recoil cylinder,
and to accommodate thermal expansion of the fluid. A replenisher
piston 130 is slideable in the reservoir chamber 131 and sealed by
an O-ring 132 around the piston head 133. The replenisher piston is
biased rearwardly by a replenisher spring 134 which surrounds the
replenisher piston rod 135 and abuts a cap 136 retained in the
forward end of the recoil piston rod 74.
If the volume of hydraulic fluid in the recoil cylinder decreases,
either through temperature decrease or leakage, the differential
pressure between the reservoir 131 and the main chamber 94 opens a
spring-biased ball check valve 138 in the piston head to provide a
conduit through which fluid may flow to replenish the supply in the
recoil cylinder.
On the other hand, as the temperature of the hydraulic fluid in the
recoil cylinder increases, the hydraulic fluid seeps forward around
the recoil piston head, which is not sealed against the walls of
the chamber. It passes through a small bleed hole 139 in the wall
of the recoil piston rod and into the replenisher reservoir, thus
forcing the replenisher piston 130 forward against the replenisher
spring. The replenisher spring 134 is considerably weaker than the
accelerator spring 100, so that expansion of the hydraulic fluid
will cause the replenisher piston, rather than the accelerator
piston 93 to move.
If expansion of the fluid is great enough, the replenisher piston
moves forward of a radial outlet 140 through the side of the recoil
piston rod so that fluid seeps out between the threads of the
adjusting nut 83 and the recoil piston rod. The external surface
141 of the recoil cylinder is circumferentially ridged to provide
an increased cooling surface, and decrease the likelihood of
overexpansion.
Because the bleed hole 139 is quite small and the recoil cycle time
is extremely short, the replenisher piston does not move
substantially under the influence of the instantaneous pressure
increase in the main fluid chamber 94 caused by recoil of the
recoil piston.
The distance which the replenisher piston rod 135 extends forward
out of the recoil piston rod 74 is proportional to the quantity of
hydraulic fluid in the recoil cylinder; hence, the replenisher
piston rod serves as a dipstick to indicate the supply of fluid by
index marks (not shown) on the dipstick which are visible through
an aperture 142 in the sleeve nut 77.
Referring particularly to FIGS. 10--12 and 27, as well as FIG. 2,
as the bolt carrier 29 reciprocates, two laterally spaced legs 148
on the forward end of the bolt carrier body 32, and two laterally
spaced legs 149 on the rear of the body 32 are guided in
longitudinal trackways 150 formed in the bottom plate 151 of the
receiver 6. Raised bearing surfaces 152, 153 and 154 located on the
upper side of the body 32 at the forward end, the center 153, and
the rear end 154 thereof respectively, slidingly engage the bottom
surface of parallel elongate guide rails 155 which are mounted
interior of the sides of the receiver. The sides of a neck portion
156 of the bolt carrier, which integrally connects the upper sleeve
portion 31 to the lower body portion 32, bear against the sides of
these rails 155 to fix the top of the bolt carrier laterally with
respect to the receiver. Thus, as the bolt carrier reciprocates
longitudinally in the receiver, the guides maintain the bolt in
axial alignment with the barrel.
Referring particularly to FIGS. 7, 10 and 27, external locking lugs
or teeth 160 at the forward end of the bolt engage with internal
locking lugs or teeth 161 at the rear end of the barrel extension
to lock the bolt to the barrel when the bolt is in battery. When
the bolt is rotated from the locking position to a position in
which the teeth 160 on the bolt are aligned with the spaces between
the teeth 161 on the barrel extension, the bolt is unlocked and may
be reciprocated rearwardly away from the barrel.
Referring now particularly to FIGS. 7, 11 and 27, the bolt 28 is
inserted in the sleeve portion 31 of the bolt carrier for axial and
rotative movement, and connected to the sleeve by a cam follower
pin 162 extending through the bolt and into radial surface cam
slots 163 on opposite sides of the bolt carrier sleeve. The cam pin
is held in place by the interior walls of the receiver 6. The
forward and rearward portions of the cam slots are parallel to the
barrel axis to permit limited axial movement of the bolt in the
carrier sleeve, with the bolt in the aligned position when the cam
follower pin 162 is in the forward portion of the slots and in the
locked position when the cam follower pin is in the rear portion.
The central portion of the cam slot is oblique to the bolt axis to
rotate the bolt between the locking position and the aligned
position. Thus, as the bolt carrier body is accelerated rearwardly
relative to the barrel by the recoil mechanism 36, the cam follower
pin cooperates with the cam slot to rotate the bolt to the aligned
position, and then carry the bolt rearward with the bolt
carrier.
When the bolt leaves the barrel it is in the aligned position, and
is extended forward in the sleeve. As is shown in FIGS. 7, 13 and
18, a spring-biased crevice pin 165, mounted in the bolt carrier
neck and sleeve for radial movement with respect to the barrel
axis, is urged upward into a notch 166 in the bolt to hold the bolt
forward in the sleeve, and therefore in the aligned position. A cam
follower or ramping pin 167 extends outwardly from the crevice pin
165 and rides on elongate cam surfaces formed on the top of the
guide rails 155 to hold the crevice pin in the upward, engaged
position after the bolt is out of battery so that the bolt remains
extended despite forces on it from stopping the bolt carrier at the
rear of the receiver and from stripping rounds during the
counterrecoil stroke. The forward edge of the crevice pin 165 is
beveled so that the bolt forces the crevice pin out of engagement
when the bolt returns to battery and strikes the barrel, while the
sleeve 31 is still moving forward in counterrecoil.
An extractor claw 168 extends forward of the bolt to grip the lip
169 of a cartridge case. The claw 168 is connected to the bolt by a
pivot pin 170 and urged into the gripping position by a spring 171.
A beveled surface 172 on the leading edge of the claw causes it to
ride up over the lip of a cartridge as the bolt moves forward to
engage a cartridge. A firing pin 173 is affixed to the rear end of
the bolt carrier sleeve by a pin 178 held in place by the walls of
the receiver 6. The firing pin 173 extends slideably through a bore
174 in the bolt. A cartridge-ejecting rod or pin 175 also extends
slideably through a bore 176 in the bolt and an arcuate aperture
177 (see FIG. 12) in the rear end of the bolt carrier sleeve. The
ejecting pin 175 is caught between the bolt and carrier sleeve by
an enlarged shoulder 180 formed intermediate its ends and
accommodated by aligned recesses in the bolt and sleeve.
Referring particularly to FIGS. 15 and 19 the buffer assembly 38 at
the rear of the receiver includes a plurality of annular cup or
Belville springs 182 stacked in series and aligned with the bolt
carrier sleeve 31. The Belville springs 182 are housed in a
cylindrical sleeve 183 mounted for longitudinal sliding movement at
the rear of the receiver. The sleeve has an integral rear end plate
184 which abuts the backplate 185 of the receiver. A plunger 186 is
longitudinally slideable in the forward end of the sleeve and is
held against the Belville springs by a stop or screw 187 slideably
extending through the plunger 186 and end plate 184 and threaded
into the back plate 185 of the receiver. The screw may be tightened
or loosened, as desired, to adjust the preloading of the Belville
springs 182.
As the bolt carrier nears the end of its recoil stroke, the rear
face 190 of the bolt carrier sleeve engages the plunger 186 and
compresses the Belville springs 182 rearwardly against the end
plate 184 of the buffer sleeve to gradually stop the recoiling bolt
and bolt carrier. The Belville springs then expand and shoot the
bolt and bolt carrier forward to the battery position for firing
another round.
The sear 41 is pivotally mounted on the lower side of the buffer
sleeve intermediate the ends of the sleeve by a pin 192 extending
through apertures in a pair of lugs 193 affixed to the sleeve. A
compression spring 194 engaged between sleeve 183 and the sear
urges the sear downward into engagement with the sear notch 42
formed in the upper surface of the bolt carrier body 32 near the
rear end of the body.
The trigger 40 is mounted on the rear plate 185 of the receiver by
a pivot pin 195. The trigger has a forward portion 44 which extends
into a notch 45 formed in the rear end of the carrier body 32 (FIG.
27) so that the forward portion of the trigger underlies the sear.
The trigger may be activated manually or by a solenoid 196 to hold
the sear up out of engagement with the sear notch so that the bolt
carrier will return to the battery position. If the trigger is
released, the spring 194 urges the sear downward to engage in the
sear notch and interrupt the counterrecoil stroke of the bolt
carrier, thereby holding the bolt carrier in the rearward cocked
position. The sear force is buffered by the sleeve 183 compressing
the Belville springs 182 forward against the screw head 188 and
plunger 186 as the sleeve 183 slides forward in the receiver (FIG.
16).
Referring particularly to FIGS. 7, 9 and 13, a long operating
spring 200 extends through an opening 201 in the bolt carrier body
32 and is compressed between the backplate 185 of the receiver and
the forward part of the bolt carrier body 32 to drive the bolt
carrier forward. The operating spring 200 is guided on a rod 202
which is affixed to the back plate of the receiver by a pin 203 and
extends slideably through a bore 204 in the front end of the
carrier body 32. A keeper 233 is slideable on the rod 202 and is
retained by an enlarged head 234 on the forward end of the rod. The
forward end of the guide rod 202 extends into the open rear end 107
of the accelerator piston 93 to support the rod when the bolt
carrier is rearward from the battery position.
A charging system is provided for pulling the bolt carrier from the
battery position rearward to the cocked position. As seen in FIGS.
1, 2 and 7 through 12, the charging system includes a chain 205
which is nested between the pairs of bolt carrier legs 148, 149 and
extends along the receiver through a central way 206 formed in the
bottom plate 151 of the receiver 6. The forward end of the chain is
connected to a charging block 207 which freely engages the forward
end of the bolt carrier body 32 as the chain is pulled rearwardly.
The block 207 travels along the way 206 on a guide rod 208 which
extends through an aperture 209 in the block into an aperture 210
at the forward end of the receiver. The rear end of the charger
guide rod is affixed to the receiver by a support 211 extending up
from the bottom plate. The chain is engaged by a sprocket 215
journaled on the bottom plate at the rear of the receiver. The
sprocket may be rotated by a removable manual crank 216 (see FIGS.
1 and 17), or by a powered means (not shown). An elongate spring
220 is guided on the rod 208 and returns the block 207 to the
forward position.
Referring to FIGS. 13 and 17, the backplate 185 of the receiver is
connected to the receiver by upper and lower removable pins 217
extending through ears 218 on the receiver and brackets 214 on the
backplate. With the pins 217 removed, the backplate may be removed
from the receiver along with the trigger 40, the solenoid 196, the
buffer 38, sear 41 an and the bolt carrier operating spring 200 and
guide rod 202, all of which are attached to the backplate. The bolt
28 and bolt carrier 29 are then free to be pulled out the rear of
the receiver whereupon the various pins 162, 178 are no longer
retained by the surfaces of the receiver and the bolt is easily
removed from the carrier and disassembled.
As is shown most clearly in FIGS. 1, 11, 20--23, 25 and 27, the
ammunition-feeding means 7 includes similar right and left hand
ammunition guides or feeding trays 228, 229 disposed on opposite
sides of the receiver 6 at the feeding station 30. Each of the
feeding trays 228, 229 guides rounds 27 of ammunition from a
different store to the feeding station 30.
The two ammunition-feeding trays 228, 229 are pivotally attached to
the receiver by a pair of vertical mounting rods 219 forward of the
tray, each extending through upper and lower ears 221 on the trays
and upper and lower brackets 223 on the receiver. As seen in FIG.
11, typically each mounting rod 219 has an upper portion 222 spring
loaded in telescoping relationship with a lower sleeve portion 224.
The two feeding trays are interconnected or ganged at their rear
ends by upper and lower horizontal connecting bars 225, 226 which
slide through corresponding keyways 227 transverse to the receiver
as the trays pivot about the forward mounting rods 219. The
connecting bars 225, 226 are connected to the trays by vertical
rear mounting rods 230 which are similar to the front mounting rods
219 and which extend through aligned apertures in the bars and in
upper and lower brackets 232, 235 extending rearwardly from the
respective trays. Each of the feeding trays can be removed from the
receiver by telescoping the mounting rods 219, 230 to remove them
from the respective brackets.
In FIGS. 20--23, 25 and 27 the right-hand tray 228 is shown in the
operative or feeding position adjacent the receiver, and the
left-hand tray 229 is pivoted away from the receiver to the
disengaged position. A selector is provided for pivoting one or the
other of the ganged ammunition-feeding trays to the operating
position to select feed from either of the ammunition stores. The
selector includes a selector handle 236 pivotally connected by a
telescoping mounting rod 237 to brackets 238, 239 fixed on the
receiver rearward of the right-hand tray. The selector handle 236
is operably connected to the right rear tray-mounting rod 230 by
upper and lower angle selector levers 240, 241 which pivot with the
selector handle 236 about the selector-mounting rod 237. One end of
each lever 240, 241 is affixed to the selector handle 236, and the
other end has a forward opening slot 242 which receives the end of
the right rear ammunition tray-mounting rod 230. As the selector
handle is pivoted rearwardly about the selector mounting rod 237,
the angle levers 240, 241 cause the ammunition feeding tray
connector bars 225, 226 to move to the right, thus pivoting the
right-hand ammunition-feeding tray laterally out of the operable
position and the left-hand ammunition-feeding tray laterally into
the operable position, as is shown in phantom in FIG. 20.
A trigger-type latch 245 (see also FIG. 17) housed in the selector
handle and pivotally mounted thereon at 246, has an arm 247 with an
indexing tab 248 on its upper side to engage in any of three
indexing notches 249, 250, 251 in the upper bracket 238. Thus, the
ammunition-feeding trays are pivoted so that the right-hand tray is
in operable position when the forward notch 249 is engaged, the
left-hand tray is in operable position when the rearward notch 251
is engaged, and both trays are out of operable position when the
intermediate notch 250 is engaged (see FIG. 28). The latch 245 is
urged into the engaging position by a spring 252 interior of the
selector handle and is released by squeezing a depending arm
253.
As the type of ammunition in one tray may have different ballistic
characteristics than the ammunition in the other tray, means are
provided for adjusting a gun gunsight responsive to the selection
of a feed tray. The sight includes a forward bead 255 and a rear
peep sight blade 256. Referring particularly to FIGS. 14 and 25,
rear sight blade 256 is mounted for vertical sliding movement in a
channel shaped bracket 254 fixed atop the receiver with the forward
side of the bracket being open. A cam follower 257 on the sight
blade engages in a cam slot 258 formed in a horizontal channel
bracket 259 fixed on the connector bar 225 and abutting the front
face of the vertical bracket 254, so as to raise the rear sight
when the left tray is operative and lower the rear sight when the
right tray is operative in accordance with the predetermined
different ballistic characteristics of the two types of
ammunition.
Referring to FIGS. 22--24 the rounds of ammunition 27 are
interconnected by an exemplary disintegrating link 262, the details
of which do not form a part of this invention except as the links
cooperate with the gun and feeding means of this invention. The
belts of ammunition of each store are fed up through the ammunition
trays alongside the receiver and then laterally inward through side
discharge openings 263 in each tray and through opposite side
openings 265 in the upper portion of the receiver which define the
feeding station 30 of the receiver. From the ammunition-feeding
station, the rounds of ammunition are stripped and chambered by the
reciprocating bolt as will be described hereinafter. The links 262
continue upward through top openings 266 in the top of each
ammunition-feeding tray where they separate from the belt and fall
from the gun.
The ammunition-feeding means 7 includes similar cam rollers 270
which cooperate with similar elongate inclined cam slots 271 formed
on opposite sides of the bolt carrier body 32 to operate the
feeding mechanism. The bolt carrier body 32 and cam slots 271 are
longer than the stroke of the bolt carrier so the cam followers 270
remain in the slots 271 throughout the stroke. The feeding
mechanisms on opposite sides of the receiver are similar; hence,
similar reference numerals will be used for the corresponding parts
of both.
Referring to FIG. 25, as well as to FIGS. 22 and 23, each cam
follower 270 is approximately centered at the feeding station 30
(see FIG. 2) and is rotatably mounted on a pawl carrier 272 by a
horizontal axle 273 near the longitudinal center of the carrier.
Each of the pawl carriers 272 is interposed between the bolt
carrier body 32 and one of the ammunition-feeding trays. The pawl
carrier 272 reciprocates vertically toward and away from the
feeding station in a rectangular opening 274 formed in the side of
the receiver. Elongate tongues 275 on the forward and rear edge of
the pawl carrier engage in corresponding vertical grooves 276 in
the side of the receiver to guide the pawl carrier in its vertical
reciprocation. A pair of similar feed pawls 277 are each pivotally
mounted on the pawl carrier, one forward of the cam follower 270
and one rearward. The pawls 277 are spring biased outward to
protrude through vertical slots 278 in the inboard sides 279 of the
corresponding ammunition feeding trays and engage the rounds of
ammunition contained in the tray. The pawls are free to pivot
upwardly but downward pivoting of the pawls is limited by the lower
end of each pawl abutting the inner wall 280 of the pawl
carrier.
As the bolt carrier moves forward, the feed pawls 277 reciprocate
downward from the position shown in FIG. 22 to that shown in FIG.
23, being cammed inwardly by a round of ammunition 27c as they pass
it. When the bolt carrier is in its forward position, the feed
pawls are beneath the round of ammunition 27c to be engaged because
the pawl springs 282 have biased the pawls outward. The pawls raise
the round 27c in the ammunition tray as the bolt carrier returns
rearward.
A pair of identical inwardly extending, spring-loaded retaining
pawls 283, only one of which is shown in FIG. 25, are pivoted up
out of the way by the round of ammunition 27c as it rises. Then the
retaining pawls return beneath the raised round 27c to retain it in
place while the feed pawls reciprocate downward to engage the next
round 27d. The retaining pawls are each pivotally mounted on a
support 284 which is on the outboard side of the feeding tray, and
are biased inward by springs 285 to engage the rounds. Downward
pivoting of the retaining pawls is limited by abutment of their
lower ends 286 (see FIG. 26) against the support 284.
An upwardly and inwardly extending plate spring 288 guides the
upper round 27a laterally to the feeding station 30, from where it
is stripped, chambered and fired. One end of the guide spring 288
is affixed to a rod 290 extending between a pair of spaced guide
arms 291 (see also FIG. 26). The other end is attached to the upper
end of the ammunition tray; and the center of the plate is bent
around a rod 292 which is fixed to the support 284 and on which the
guide arms 291 are pivotally mounted.
The side opening 263 in each tray has a rear portion 302 which is
narrower than the diameter of the rear part of the round 27 and a
forward portion 300 which is wider than the widest part of the
round 27. The opening 263 is contiguous with an opening 301 in the
forward wall of the tray. The raised round 27 is held in the tray
since it cannot pass completely through the narrow rear portion 302
of the opening. However, the round 27 does protrude far enough
through the side opening 263 of the tray, under the urging of
spring plate 288, that if the tray is in the operating position,
the bolt 28 engages the rear of the round as the bolt comes
forward. The bolt 28 strips the round 27 out of the links 262 and
rams the round forward and inward through the forward portion 300
of the side opening 263 and the opening 301 into the chamber of the
barrel.
The empty links 262 are guided up out of the openings 266 in the
top of the ammunition trays by forwardly and rearwardly extending
tabs 293 on the links (see FIG. 24) which engage in vertical guide
grooves 294 in the upper end of the spaced guide arms 291.
A positioning stop 295 engages the round 27a at the feeding station
30 to positively limit upward movement of the round and fix it at
the feeding station. This stop is pivotally mounted about a
horizontal transverse axis on the upper plate 296 of the ammunition
tray so that as the round moves forward to the chamber, the stop is
cammed forward out of the way by the cartridge case. A spring 297
returns the stop to its operative position. The forward end of the
round is guided into the chamber by a ramp guide 299 on the forward
end of the ammunition tray and tapered surfaces 298 on the locking
teeth 161 adjacent opposite sides of the barrel extension (see FIG.
21).
When an ammunition tray is pivoted to the inoperative position, as
for example the left-hand tray in FIGS. 22 and 23 and both trays in
FIG. 28, the feed pawls will continue to reciprocate vertically as
the bolt carrier reciprocates, but the rounds of ammunition in the
tray are far enough outboard of the feed pawls that the pawls do
not engage the rounds, and no ammunition is fed from that tray
tray. The top round is held in the tray since it cannot pass
through the rear portion 302 of the side openings 263 far enough to
be engaged by the bolt. Since the retaining pawls are part of the
tray they remain effective to support the rounds in the tray so it
is ready to feed ammunition when pivoted to the operative
position.
The outboard side plate 303 of each ammunition tray is designed to
be opened for access to the interior of the tray. The sideplate is
pivotally attached to the forward vertical mounting rod 219 by a
bracket 304 affixed to the forward end of the sideplate and having
ears 305 through which the mounting rod is inserted. The rear edge
306 of the sideplate extends rearward of the ammunition-feeding
tray so that it may be gripped to pivot the sideplate to the open
position.
With the sideplate open, the ammunition in the tray may be removed
by pulling upwardly on a U-shaped release handle 307. The release
handle 307 is an extension of a U-shaped connector 309, the ends of
which are attached around the guide plate support rod 290. As the
release handle 307 is pulled, the guide arms 291 pivot outwardly to
pull the guide plate spring 288 away from the rounds of ammunition
as shown in phantom in FIG. 22. The release handle is also
connected to the retaining pawls 283 by wires 308 attached to the
connector 309. The wires 308 pull the retaining pawls outwardly
from under the rounds of ammunition when the release handle 307 is
pulled. The rounds can then be pulled downward out of the tray to
unload the gun.
The operation of the gun can best be understood by following
through a complete firing cycle beginning with the gun in the
firing position shown in FIG. 2. When the round is fired, the
barrel 5 recoils rearwardly in the receiver 6. The recoil piston 73
which is affixed to the barrel moves rearwardly in the stationary
recoil cylinder 70 as the barrel recoils, thereby driving the
accelerator piston 93 rearwardly. Since the cross-sectional area of
the recoil piston head 75 is larger than that of the accelerator
piston head 95, e.g. by a ratio of 3 to 2, the accelerator piston
moves rearward faster than the barrel and recoil piston.
The rear end of the accelerator piston rear extension 107 engages
the forward end of the bolt carrier body 32 to drive the bolt
carrier rearward at an accelerated rate relative to the barrel.
When the barrel has completed an initial part of its recoil, e.g.
one-half inch, the accelerator piston 93 has moved rearward a
sufficient distance, e.g. three-quarters of an inch, to bottom out
in the recoil cylinder 70, as shown in FIG. 7. By that time the
accelerator piston has imparted sufficient momentum to the bolt
carrier 29 to send the bolt carrier and bolt 28 rapidly to the rear
of the receiver. Also by then, the forward face of the recoil
piston head 75 has passed the forward edge of the wedge-shaped
throttling groove 110 in the cylinder wall, so that the groove
becomes effective to pass fluid around the recoil piston head. The
throttling groove decreases in cross-sectional area in the rearward
direction, so that the quantity of fluid which passes through it
decreases at a programmed rate as the recoil piston moves rearward,
thereby cooperating with the recoil spring 98 to buffer the recoil
force of the barrel and bring the barrel and recoil piston to a
stop with the recoil piston slightly spaced from the accelerator
piston forward extension 101, and the barrel extension 48 slightly
spaced from a shoulder 310 on the receiver, as shown in FIG. 8.
As is shown in FIG. 7, during the first part of the recoil cycle,
the bolt 28 is locked to the barrel by the locking teeth 160, 161
while the bolt carrier moves rearward at a faster rate than the
bolt and barrel and the bolt cam follower pin 162 moves through the
rearward axial portion of the bolt carrier sleeve cam slots 163. By
the time the bolt carrier has traveled rearwardly with respect to
the barrel and bolt sufficiently so that the cam follower 162 of
the bolt enters the central portion of the cam slots 163 to rotate
the bolt to the unlocked or aligned position, the residual pressure
in the barrel chamber has been somewhat dissipated, thereby
reducing the friction between the teeth 160, 161 of the bolt and
barrel. After the bolt is in the aligned or unlocked position a
further short dwell period occurs while the cam pin 162 moves
through the forward portion of the sleeve cam slots 163. As the cam
pin engages the forward end of the cam slots, the bolt moves
rearward with respect to the barrel and the extracting claw 168
which is engaged with the lip of the expended cartridge, extracts
the cartridge from the chamber and carries it rearward with the
bolt. Extraction of the cartridge from the chamber occurs between
the positions illustrated in FIGS. 7 and 8 so that the barrel is
still recoiling, even though it is in its deceleration phase. Thus,
the relative velocity between the bolt and the barrel as the
cartridge is removed, is less than if the barrel were stopped, so
that removal of the cartridge is eased.
When the bolt 28 begins to move rearward away from the barrel, the
bolt carrier sleeve 31 is rearward with respect to the bolt, and
the crevice pin 165 is urged upward by the spring 164 into the
notch 166. After the bolt leaves the barrel, the ramping pin 167
holds the crevice pin engaged in the notch to keep the bolt in the
aligned position until its locking teeth 160 are again engaged in
those 161 of the barrel.
Referring now to FIG. 9, as the bolt and bolt carrier continue
rearward with the cartridge case, the recoil spring 98 and
accelerator spring 100 urge the accelerator piston 93, recoil
piston 73 and barrel 5 forward in counterrecoil to the position
shown in FIG. 2. During the initial part of the counterrecoil cycle
of the barrel, fluid passes the recoil piston head 75 both through
the wedge-shaped throttling groove 110 and through the orifices 123
as the one way flapper valve 122 in the recoil piston head opens
(see FIG. 3a). After the recoil piston head moves forward of the
throttling groove 110, only the orifices 123 are effective to pass
fluid through the piston head 75, and therefore the recoil piston
is throttled down. The orifices 123 are sized to permit the barrel
to counterrecoil fast enough to be in battery before a new round is
stripped, but slow enough to reduce the impact at the end of the
counterrecoil stroke. As the counterrecoil cycle of the barrel is
completed, the recoil piston 75 head abuts the counterrecoil
Belville springs 127 in the recoil cylinder to buffer the
counterrecoil force of the barrel and bring it to a stop.
Meanwhile, the bolt and bolt carrier have reciprocated to the
rearward position shown in FIG. 13 where the expended cartridge is
immediately below an ejection port 311 in the upper side of the
receiver, and the ejecting pin 175 abuts the plunger 186 of the
rear buffer assembly. As the bolt carrier continues rearward from
the position of FIG. 13 to that of FIG. 14, the bolt 28 and bolt
carrier 29 move rearward with respect to the ejecting pin 175,
causing the forward end of the ejecting pin to strike the expended
cartridge throwing it loose from the pivotal claw 168 and upward
out of the ejection port 311. The Belville springs 182 buffer the
ejection force.
The rear face of the bolt carrier sleeve 31 engages the plunger 186
causing the Belville springs to compress rearwardly, thereby
buffering the recoil force of the bolt and bolt carrier. As shown
in FIG. 15, after the recoil of the bolt and carrier is stopped,
the Belville springs 182 expand and push the bolt carrier forward.
If the sear 41 is in the lowered position, as shown in FIG. 15, it
engages in the sear notch 42 of the bolt carrier to stop the
forward movement of the bolt carrier. As shown in FIG. 16, the sear
force is buffered by the Belville springs 182 of the buffer
assembly, since the bolt carrier forces the sear 41 and buffer
sleeve 183 forward to compress the Belville springs forwardly
against the screw head 188. The parts then come to rest in about
the position illustrated in FIG. 15.
As the bolt carrier reciprocates rearwardly in recoil, the
ammunition-feeding pawls reciprocate upward from the position shown
in FIG. 23 to that shown in FIG. 22, thereby raising a round of
ammunition 27a up and into the feeding station in front of the bolt
as shown in FIGS. 20 and 22.
If the sear 41 is disengaged by the trigger 40, or was not in the
lowered position at the end of the recoil stroke, the bolt carrier
is returned forward to the battery position by the Belville springs
182, and the bolt carrier operating spring 200. As the bolt and
bolt carrier move forward, the bolt 28 engages the rear of the
round of ammunition 27 at the feeding station, as shown in FIGS. 21
and 27, and rams the round forward into the chamber of the
barrel.
As the bolt and bolt carrier continue forward toward the position
of FIG. 2, the bolt teeth 160 pass through the locking teeth 161 of
the barrel extension and then engage the barrel itself to stop
forward movement of the bolt. The bolt carrier 29, however,
continues forward, camming the crevice pin 165 out of the notch
166, and rotating the bolt 28 to the locking position as the bolt
cam pin 162 passes through the central portion of the sleeve cam
slots 163. When the bolt carrier reaches the position illustrated
in FIG. 2, the forward end of the bolt carrier sleeve 31 strikes
the rear end of the barrel extension 48 to stop the bolt carrier.
The counterrecoil momentum of the bolt carrier is transmitted
through the relatively heavy barrel and the recoil piston 73, and
is buffered by the Belville springs 127 in the recoil cylinder. At
the same time, the firing pin 173 is driven by the bolt carrier
through the opening 174 in the bolt to strike the round of
ammunition and fire it, thereby causing the cycle to be
repeated.
Referring to FIG. 22, the rounds of ammunition from the right and
left feeding trays 228 228, 229 enter the feed station from
opposite quadrants with respect to the barrel axis, while the empty
cartridges are ejected upward into a third quadrant, and the bolt
carrier body 32 extends downward into a fourth quadrant. Thus,
interference between the fast moving bolt carrier 29 and the rounds
27 is avoided.
It is indicative of the velocities, and forces involved in the
operation of this gun, that a typical gun in accordance with this
invention is designed to fire 25mm, shells at approximately 700
rounds per minute, using a barrel weighing approximately 50 pounds
and a bolt carrier of approximately 12 pounds reciprocating at a
velocity of about 45 feet per second.
Referring now to FIG. 29, an alternative embodiment of the recoil
and accelerator mechanism is shown. That embodiment includes a
recoil cylinder 312 and recoil piston 313 connected to the barrel 5
and receiver 6 in substantially the same manner as the recoil
cylinder 70 and piston 73 of FIGS. 3a and 3b. The recoil cylinder
312 does not contain hydraulic fluid, however. An accelerator lever
314 is pivoted in the receiver at 315 and engages the forward end
of the bolt carrier body 32. An accelerator piston rod 316, which
extends rearward from the recoil piston head 317, is pivotally
connected to the arm at 318 by a link 319. The ratio of the
distance between the two pivotal connections 315, 318 on the arm,
and the length of the arm, is selected to obtain the desired rate
of acceleration of the bolt carrier body 32 relative to the barrel
5.
The recoil piston head 317 moves rearwardly in recoil with the
barrel and during the initial part of the recoil, is resisted only
by a relatively weak compression spring 320 rearward of the piston
head. After the recoil piston head 317 has moved rearwardly a
selected initial distance, it engages a plunger 322 which abuts a
plurality of Belville springs 323 stacked in series-parallel to
form a relatively strong spring which buffers the recoil force of
the barrel 5 and returns the barrel to the forward position while
the bolt carrier 29 continues rearward. Counterrecoil of the barrel
is buffered by the forward Belville spring 324 as in the embodiment
of FIGS. 3a and 3b. The spring and link-type buffering and
accelerator system, as illustrated in FIG. 28, is usable in small
weapons where the recoil and counterrecoil forces, and the weight
of the barrel and bolt carrier are less in the gun illustrated in
FIG. 2.
FIG. 30 illustrates a control circuit for controlling the rate of
fire of the automatic gun, for example between full automatic and
semiautomatic. Frequently full automatic firing is desirable when
using high explosive rounds of ammunition. For armor-piercing
rounds however it is usually desirable to fire semiautomatic so
that the gun can be aimed for each round.
As can be seen in FIG. 20, a normally open selector switch 330 has
an arm 331 engageable by the selector lever 241 to close the switch
when the selector lever is pivoted to the phantom line position,
thus moving the left-hand ammunition-feeding tray 229 containing
high explosive rounds into operative relationship with the bolt and
feed pawls and moving the right-hand ammunition-feeding tray 228
containing armor-piercing rounds out of operative position. This
prepares the gun for automatic fire.
As seen in FIG. 30, the manual depression of a firing button 332
located at a remote control station 334 will continue to energize
the firing solenoid 196 from a battery 336 for so long as the
firing button 332 remains depressed, provided that the selector
switch 330 is closed. This is the automatic firing condition.
If, however, the selector switch 330 is in its normally open
condition for semiautomatic firing of armor-piercing rounds from
the right-hand feeding tray, the depression of the firing button
332 at the control station energizes the firing solenoid 196 only
through the normally closed contact 339 of a control relay 341. The
control relay 341 is energized by depressing the firing button 332,
however it is relatively slow acting compared to the firing
solenoid 196, the timed relationship being such that the firing
solenoid 196 actuates the trigger 40 to fire a single round prior
to the opening of the normally closed contact 339 of the control
relay.
Thus, the selector switch 330 and associated circuitry, being
responsive to position of the selector lever 241, provides a means
for controlling the firing rate of the gun in accordance with the
ammunition store selected.
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