 |
Claims  |
|
|
I claim:
1. A gas operated gun for firing a live cartridge of predetermined length
comprising a case, a propellant within said case and a bullet at one end
of the case arranged to be driven by said propellant, said gun including a
receiver having a rear wall at one end and a barrel at the other end
thereof, said receiver also having a cartridge feed station, a bolt means
movable within said receiver, a main drive spring arranged to cooperate
with the bolt means and to urge the bolt means toward the barrel, whereby
the product of sprung weight.times.spring force.times.cycling distance is
equal to (0.5I).sup.2 .times.0.5g .+-.15%, where sprung weight is the
total weight in kilograms of all components driven toward the barrel by
the main drive spring, the spring force is an average value of spring
forces that decelerate the sprung weight as said sprung weight travels
away from said barrel and which accelerates the sprung weight as it
travels forwardly toward said barrel, cycling distance is the length of
allowable travel of the bolt means in meters, I is the cartridge impulse
and g is acceleration due to gravity, the receiver and bolt means being
arranged so that the bolt means does not impact said rear wall.
2. A gas operated gun as claimed in claim 1 wherein the rearward travel of
the bolt means is resisted solely by the compression of the main drive
spring.
3. A gas operated gun as claimed in claim 2 wherein said bolt means is
movable solely within said receiver.
4. A gas operated gun as claimed in claim 3 wherein a gas means is provided
a predetermined distance along said barrel to provide rearward impetus to
the bolt means and the main drive spring is mounted on a guide means which
is located forwardly adjacent said gas means and rearwardly adjacent said
receiver wall.
5. A gas operated gun as claimed in claim 4 wherein a buttstock is provided
and the rearward location of the guide means is on the interior of the
rear receiver wall with the exterior rear receiver wall being in abutting
relationship with the buttstock.
6. A gas operated gun for firing a live cartridge of predetermined length
comprising a case, a propellant within said case and a bullet at one end
of the case arranged to be driven by said propellant, said gun including a
receiver having a rear wall at one end and a barrel at the other end
thereof, said receiver also having a cartridge feed station, a bolt means
movable within said receiver, a main drive spring arranged to cooperate
with the bolt means and to urge the bolt means toward the barrel, whereby
the product of sprung weight.times.spring force.times.cycling distance is
equal to (0.5I).sup.2 .times.0.5g .+-.15%, where sprung weight is the
total weight in kilograms of all components driven toward the barrel by
the main drive spring, the spring force is an average value of spring
forces that decelerate the sprung weight as said sprung weight travels
away from said barrel and which accelerates the sprung weight as it
travels forwardly toward said barrel, cycling distance is the length of
allowable travel of the bolt means in meters, I is the cartridge impulse
and g is acceleration due to gravity, the receiver and bolt means being
arranged so that the rearward travel of the bolt means is resisted solely
by the compression of the main drive spring so that the bolt means does
not impact said rear wall, and feed overtravel is provided at least equal
to the overall length of a live cartridge.
7. A gas operated gun as claimed in claim 6 wherein I is given by
##EQU9##
8. A gas operated gun as claimed in claim 6, wherein for a standard
5.56.times.45 mm cartridge,
I=0.597 kp-secs.
9. A gas operated gun as claimed in claim 6, wherein the product of sprung
weight.times.spring force.times.cycling distance is equal to (0.5I).sup.2
.times.0.5g.+-.5%.
10. A gas operated gun as claimed in claim 6, wherein the gun is arranged
to fire from the open bolt position in which the bolt means is held behind
the feed station by the previous cycle of the bolt means being interrupted
prior to a new cycle starting with the bolt means being driven forwardly
toward the barrel by the main drive spring.
11. A gas operated gun as claimed in claim 6, wherein the bolt means
comprises a reciprocable bolt carrier assembly and a bolt carried thereby.
12. A gas operated gun as claimed in claim 11, wherein the bolt is movable
over a predetermined distance with respect to the bolt carrier assembly.
13. A gas operated gun as claimed in claim 11, wherein at a predetermined
length along the barrel there is provided a gas port and connected with
the gas port a cylinder containing a piston, saidpiston being arranged to
contact and provide rearward impetus to the bolt carrier assembly which
assembly is extended forwardly longitudinally with the barrel to the
region of said gas port.
14. A gas operated gun as claimed in claim 13, wherein the main drive
spring is mounted on a guide means which is located forwardly adjacent
said cylinder and rearwardly adjacent the receiver rear wall.
15. A gas operated gun as claimed in claim 14, wherein a buttstock is
provided and the rearward location of the guide means is on the interior
of the rear receiver wall with the exterior rear receive wall being in
abutting relationship with the buttstock.
16. A gas operated gun as claimed in claim 6, wherein the gun is arranged
to fire from the open bolt position in which the bolt means is held behind
the feed station by the previous cycle of the bolt means being interrupted
prior to a new cycle starting with the bolt means being driven forwardly
toward the barrel by the main drive spring.
17. A gas operated gun as claimed in claim 6, wherein the bolt means
comprises a reciprocable bolt carrier assembly and a bolt carried thereby.
18. A gas operatd gun as claimed in claim 17, wherein the bolt is movable
over a predetermined distance with respect to the bolt carrier assembly.
19. A gas operated gun as claimed in claim 17, wherein at a predetermined
length along the barrel there is provided a gas port and connected with
the gas port a cylinder containing a piston, said piston being arranged to
contact and provide rearward impetus to the bolt carrier assembly which
assembly is extended forwardly longitudinally with the barrel to the
region of said gas port.
20. A gas operated gun as claimed in claim 19, wherein the main drive
spring is mounted on a guide means which is located forwardly adjacent
said cylinder and rearwardly adjacent the receiver rear wall.
21. A gas operated gun as claimed in claim 20, wherein a buttstock is
provided and the rearward location of the guide means is on the interior
of the rear receiver wall with the exterior rear receiver wall being in
abutting relationship with the buttstock.
22. A gas operated gun for firing a live cartridge or predetermined length
comprising a case, a propellent within said case and a bullet at one end
of the case arranged to be driven by said propellent, said gun including a
receiver having a rear wall at one end and a barrel at the other end
thereof, said receiver also having a cartridge feed station, a bolt means
movable within said receiver, said bolt means comprising a reciprocal bolt
carrier assembly and a bolt carried thereby, said bolt being movable over
a predetermined distance with respect to the bolt carrier assembly, said
barrel having positioned at a predetermined length therealong a gas port,
and connected with the gas port there being a cylinder containing a
piston, said piston being arranged to contact and provided rearward
impetus to the bolt carrier assembly which assembly is extended forwardly
longitudinally with the barrel to the region of said gas port, a main
drive spring arranged to cooperate with the bolt means and to urge the
bolt means toward the barrel, said main drive spring being mounted on a
guide means which is located forwardly adjacent said cylinder and
rearwardly adjacent the receiver rear wall, whereby the product of sprung
weight.times.spring force.times.cycling distance is equal to (0.5I).sup.2
.times.0.5g .+-.15%, where sprung weight is the total weight in kilograms
of all components driven toward the barrel by the main drive spring, the
spring force is an average value of spring forces that decelerate the
sprung weight as said sprung weight travels away from said barrel and
which accelerates the sprung weight as it travels forwardly toward said
barrel, cycling distance is the length of allowable travel of the bolt
means in meters, I is the cartridge impulse and g is acceleration due to
gravity, the receiver and bolt means being arranged so that the bolt means
does not impact said rear wall.
23. A gas operated gun as claimed in claim 22 wherein the rearward travel
of the bolt means is resisted solely by the compression of the main drive
spring.
24. A gas operated gun as claimed in claim 22 wherein feed overtravel is
provided at least equal to the overall length of a live cartridge.
25. A gas operated gun as claimed in claim 22 wherein a buttstock is
provided and the rearward location of the guide means is on the interior
of the rear receiver wall with the exterior rear receiver wall being in
abutting relationship with the buttstock. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
This invention relates particularly to gas operated automatic guns,
although it may also be used with semi-automatic guns.
Automatic guns are well known and the term is applied to a gun in which,
when a trigger is pulled, a plurality of cartridges are fired serially for
as long as the trigger is held or until the last cartridge is fired.
Semi-automatic guns are similarly well known and the term is usually
applied to a gun which, when a trigger is pulled, fires a cartridge,
subsequently ejects the cartridge, cocks the bolt and chambers a next
cartridge automatically but does not fire said next cartridge until the
trigger is released and again pulled to repeat the cycle.
Automatic and semi-automatic guns are well discussed in literature and
examples are "Small Arms of the World" by W. H. B. Smith, tenth edition
completely revised by Joseph E. Smith published by Stackpole Books,
Harrisburg, Pennsylvania, U.S.A., and "Janes Infantry Weapons" 1977,
edited by Dennis H. R. Archer, published by Janes Publishing Company, and
a known type of gas operated, automatic gun is the United States 7.62 mm
NATO M60 machine gun described at pages 695-699 in "Small Arms of the
World" and pages 332-337 of "Janes Infantry Weapons" and the 5.56 mm AR18
rifle described at page 656 in "Small Arms of the World" and pages 229-231
of "Janes Infantry Weapons".
There are three principle types of automatic guns, namely recoil operated,
blow-back operated and gas operated. The recoil operated gun is generally
not suitable for a hand held weapon because it is sensitive to mount
stiffness and elevational altitude. Blow-back guns, though still in use by
infantry, are operable only with low power, short-range cartridges and,
thus, the gas operated gun is preferred by present day infantry because of
its improved reliability since it is not so susceptible to fouling by mud
and grit, etc., and because it can use a reasonably high power cartridge.
A gas operated gun, such as the AR18, has a receiver housing, a bolt/bolt
carrier assembly which is urged toward a barrel by a drive spring and
actuated by a trigger through the intermediary of a sear. A radial
drilling through the wall of the barrel is provided at a predetermined
distance along the barrel length and externally in co-operation with the
drilling is a gas piston and cylinder assembly. In operation, the
bolt/bolt carrier assembly strips and feeds a cartridge from a magazine
into a feed area within the receiver and the bolt drives the cartridge
over a feed ramp within the normally provided barrel extension to chamber
the cartridge. The bolt is usually then rotated into a locked position so
that the cartridge is securely held within the chamber. Either a hammer is
then released to strike the firing pin or the final forward momentum of
the bolt carrier assembly rotates and locks the bolt as it drives the
firing pin into the cartridge to thereby discharge the cartridge. Gas
pressure is produced by the firing action of the cartridge, which gas
enters the radial drilling once the bullet has passed the drilling and
enters the gas cylinder whilst the bullet is still within the barrel. Of
course, once the bullet leaves the barrel the gas is dissipated. The
cylinder, arranged to be the movable part, is connected to the bolt
carrier assembly by a rod so that as the cylinder fills with gas it is
driven by the gas, the bolt carrier is driven rearwardly thereby unlocking
the bolt, extracting the spent cartridge, ejecting the same and cocking
the gun for a further series of operations. A further, similar, cycle is
then produced for as long as the trigger is squeezed and, of course, for
as long as there are cartridges to provide the gas discharge. It is to be
noted that the movable cylinder, or where appropriate piston, does not
necessarily have the same length of travel as the bolt carrier assembly.
The AR18 rifle, along with several other automatic weapons, fires from a
closed bolt position, which means that the bolt/bolt carrier assembly are
all the way forward and a round has been chambered by the preceding cycle
so that, when the trigger is pulled, only the hammer or other lightweight
firing mechanism moves; the bolt and carrier assembly do not move until
after firing takes place and there is no consequential motion or force
applied to the gun before the instant of firing. This is in distinction to
a gun which fires from the open bolt position (such as an M60 machine gun)
where the bolt/bolt carrier assembly are held back behind the feed area by
the previous cycle being interrupted and the bolt carrier being caught by
a sear before the bolt/bolt carrier assembly are driven all the way
forward by the drive spring. Thus, initially no cartridge has been
chambered and when the trigger is pulled the bolt/bolt carrier assembly is
released and driven forward by the main spring to then chamber and fire
the cartridge. When firing from the open bolt position there is a rearward
force applied to the gun before the instant of firing due to the reaction
of the drive spring in pushing the bolt carrier forward.
In the cycle of operations, the bolt carrier travels to a rearward position
so as to permit a further round to be fed and chambered. Such feed
overtravel is defined herein as the distance in meters between the front
of the bolt (in its extended position relative to the bolt carrier) and
the base of the cartridge in the feed, e.g. the magazine delivery port,
measured with the rear of the bolt carrier just touching the positive stop
which includes a buffer if present. Note the front of the bolt is usually
the stripping shoulder that contacts the base of the cartridge and drives
the cartridge forward, out of the feed, and towards the chamber as the
bolt carrier assembly moves forward. The term "stripping shoulder" applies
(instead of "front of the bolt") to weapons that do not strip with the
front of the bolt.
In known gas operated guns it is normal for the bolt carrier to impact the
rear wall of the receiver to limit the extent of rearward travel, and in
many known guns, such as the M16, described at pages 650-653 in "Small
Arms of the World" and pages 226-228 of "Janes Infantry Weapons", the
impact is through the intermediary of a buffer.
By the term "buffer", as used herein, is meant a means which is interposed
between the bolt carrier assembly and the stop to rapidly retard the bolt
carrier and which has a force at least twice greater than that of all the
other combined spring force averages.
So as to achieve reliability, any automatic or fully automatic gun must
provide the bolt/bolt carrier with sufficient energy for the bolt/bolt
carrier to overtravel the cartridge feed station and such overtravel must
be sufficiently great to allow time for the cartridge to travel to a
position whereby it may be stripped by, for example, the stripping
shoulder of the bolt from the cartridges with which it is stacked.
Although gas operated guns are less susceptible to fouling they do become
dirty and for this reason a gun designer must provide the bolt/bolt
carrier assembly with sufficient energy to overtravel the feed station
even when the gun is operating in a dirty condition. For this reason, some
gas operated guns are provided with a manually adjustable gas controlled
system so that a user may increase the gas pressure if the experience is
found that cartridges are not permitted sufficient time to move to a feed
position. In gas operated guns where no gas system control is provided the
gas system is arranged to provide the bolt/bolt carrier assembly with
sufficient energy to overtravel the feed station under the adverse
conditions.
However, as described above for the M16 assault rifle, it is normal for the
rearward extent of travel of the bolt carrier to be limited by a buffer
impacting the rear wall of the receiver, and the buffer is provided in an
attempt to absorb the shock of the bolt carrier impacting the rear
receiver wall. The bolt carrier with or without a buffer bounces off the
rear wall of the receiver and it will be realised that by increasing the
gas pressure in the gas system to increase the energy driving the
bolt/bolt carrier assembly rearwardly, so the energy with which the bolt
carrier strikes the receiver wall will increase. This has the effect that
the travel time from the minimum overtravel position, which permits a
cartridge sufficient time to move to the feed station, to the time the
bolt stripping shoulder is driven forwardly by the main spring and attempt
to strip a cartridge is reduced, because the bolt carrier assembly is
driven rearwardly faster and bounces off the rear wall and returns
forwardly faster. Thus, if the energy imparted to the bolt/bolt carrier
assembly by the gas pressure exceeds a predetermined value so, once again,
insufficient time is permitted for a cartridge to move to the feed
station.
In gas operated guns numerous attempts have been made to lessen the effect
of the bolt carrier striking the rear receiver wall, although these
attempts have been made for the sake of reducing the shock effect of the
bolt carrier assembly driving the rear wall of the receiver in a backward
direction. The term "restitution" is applied to this phenomenon and means
a proportion of energy from an impacting mass which is returned to that
mass upon striking a fixed, solid object. Thus, if a steel bolt carrier
strikes a steel rear wall of the receiver, most of the energy of the
impacting carrier assembly will be returned to the carrier in the opposite
direction by the rear receiver wall. In such an instance there is
approaching 100% restitution, and the AR18 is an example.
In the M16 rifle, an attempt has been made to reduce restitution by
providing a buffer carrier by the rear bolt carrier assembly so as to
absorb some of the energy of the impacting bolt on the rear receiver wall.
The buffer is compressible between the rear receiver wall and the rear of
the impacting bolt carrier assembly. Although the coefficient of
restitution of the M16 is considered to be low, it is still found that
significant recoil is caused by the rear receiver wall being impacted by
the bolt/bolt carrier assembly and, by direct correlation, so the
bolt/bolt carrier assembly rebounds with a significant amount of energy.
It is one object of this invention to provide a gas operated gun in which
the aforementioned adverse effects of impact relative to reliable feed of
known weapons are substantially mitigated.
According to one aspect of this invention there is provided a gas operated
gun including a receiver having a rear wall at one end and a barrel at the
other end, the said receiver also having a cartridge feed station, and
movable within the receiver a bolt means arranged to co-operate with a
main drive spring which urges the bolt means toward the barrel, the
arrangement of the receiver and bolt means being such that feed overtravel
is provided equal to or greater than the overall length of a live
cartridge.
By utilising a construction where the feed overtravel is equal to or
greater than the overall length of a live cartridge, an exceptional amount
of overtravel, compared with known gas operated guns, is provided and so
the time permitted for a cartridge to move to the feed station is greatly
increased. With the arrangement of the present invention, the rearward
extent of travel of the bolt means is normally such that it does not
impact the rear receiver wall and so the problems of rebound associated
with impact are, hence, overcome. As noted above, known gas operated guns
suffer from recoil blow and not only is there is a recoil from the gun
when the bolt carrier assembly strikes the rear receiver wall, but there
is also a recoil blow from the gun when the cartridge fires. There are,
thus, two recoil spikes which occur at opposite ends of a time cycle, i.e.
one spike is when the bolt carrier assembly is at its rearmost position
and the other spike is when the bolt carrier assembly is at its foremost
position adjacent to the barrel. The effect of recoil upon the user of the
gun is that whilst the first round may be on target, subsequent rounds
cause the barrel of the weapon to rise so that shots are fired above
target. It must be remembered that such automatic weapons usually fire of
the order of 10-rounds per second and it takes some time, of the order of
1-2 seconds, before the user of the weapon is able to compensate for the
recoil effect and bring his aim back on to target. Such weapons, due to
loss of control by the user, tend to be inaccurate.
Although the loss of control can be substantially mitigated in both the
previously mentioned blow-back and recoil guns, the solution employed in
those guns have not heretobefore been thought applicable to gas operated
guns because of the operational differences between the types of guns.
The recoil effect of a gas operated gun is normally considered less than
that of a bolt action gun which, although not automatic, contains many
similarities with a gas operated gun. In this respect, they both have a
locked and rigid structure that tries to deliver the cartridge impulse
during "bore" time. The lighter recoil has been attributed to the gas in
the cylinder not only driving the moving memeber (be it the cylinder or
piston) and thereby the free mass of the bolt carrier assembly rearwardly,
but also the gas driving the front wall of the fixed member in a forward
direction. Thus, gas operated guns tend to have a "softer" action than the
aforesaid bolt action gun. Nonetheless, the effect of recoil is still as
described above, i.e. the user loses aim after the first shot has been
fired and it is evident that the cause of the user losing aim is because
of the number of differing recoil actions that occur which are experienced
by a user as a series of separate sharp blows. Various attempts to
overcome recoil have been made and reference may be paid to "Hatcher's
Note Book" by Julian S. Hatcher, published in the United States of America
by the Telegraph Press, 3rd Edition, 2nd printing April 1976, page 262 et
seq.
Because of the action of recoil on the controllability of known gas
operated guns, efforts to improve the hit probability of such gas operated
guns include three shots bursts limiters, high rate rifles that fire three
to four shots extremely quickly so that the gun does not have time to move
of target and duplex or triplex cartidges that fire two or three bullets
with each shot. None of these devices have proved successful and have
merely shown the desperation of designers to improve the accuracy of a gas
operated automatic gun. It is a further object of this invention to
improve controllability of a gas operated gun.
According to a further aspect of this invention there is provided a gas
operated gun including a receiver having a rear wall at one end and a
barrel at the other end, said receiver also having a cartridge feed
station, and movable within the receiver a bolt means arranged to
co-operate with a main drive spring which urges the bolt means toward the
barrel whereby the product of sprung weight.times.spring
force.times.cycling distance, each as hereinafter defined, is equal to
(0.5I).sup.2 .times.0.5 g.+-.15% where I is cartridge impulse and g is
acceleration due to gravity, the receiver and bolt means being arranged so
that the bolt means does not impact a positive stop and feed overtravel is
provided equal to or greater than the overall length of a live cartidge.
Normally I is given by
##EQU1##
and as an example, for a standard 5.56.times.45 mm cartridge,
##EQU2##
By "spring force" is meant herein an average value of spring forces that
decelerate the sprung weight (as hereinafter defined) as it travels
rearward and accelerate the weight as it travels forward. The avergae is
determined by distance, not by time. If the weight cocks a hammer or other
firing mechanism as it travels rearward the force of the spring of such a
firing mechanism is part of the average. The sum total of all spring force
averages, whether they add or subtract from the main drive spring,
determines the "spring force" but does not include the force of a buffer.
The "spring force" excludes friction which cannot be accurately measured.
It is determined by standard spring mathematical formulae as defined by
the Associated Spring Corporation headquatered at the Wallace Barnes
Division, 18, Main Street, Bristol, Connecticut 06010, United States, an
internationally recognised authority. Thus, where a swinging hammer is
employed the product sprung weight.times.spring force.times.cycling
distance is given by:
1/2[(EC+EH)(WC+WH)+(EC. WC.+EH. WH.)]
where EC=energy of bolt carrier assembly
EH=energy of hammer
WC=weight of carrier in kg.
WH=weight of hammer in kg.
and
EC=average bolt carrier assembly main spring force.times.bolt carrier
assembly cycling distance in mKg.
EH=average hammer spring force.times.hammer spring deflection distance in
mKg.
It will be appreciated by those skilled in the art that where a torsion
spring is employed for the hammer a direct conversion can be made to
linear values.
By "sprung weight" is meant the total weight in kilograms of all components
driven forward by the main spring. For a gas operated gun these usually
include, but are not limited to, the bolt assembly, bolt carrier (or
operating rod assembly, known per se) and half the weight of the main
drive spring. When applicable, it would also include the cocking handle
(as in the known AK-47) and buffer if the buffer travels with the bolt
carrier as in the M-16.
The term "cycling distance", used herein, is defined as the length of
allowable travel of the bolt carrier (or operating rod assembly) measured
in meters. Distance is for half cycle and is the total length the bolt
carrier (or operating rod assembly known per se) can move from the front
of the receiver to the rear without hitting a "positive stop", by which
term is also meant to be included a buffer.
In a currently preferred embodiment the product of sprung weight
.times.spring force .times.cycling distance is equal to (0.51).sup.2
.times.0.5g.+-.5%. Preferably, the gun is arranged to fire from the open
bolt position as hereinbefore defined.
Conveniently, the bolt means comprises a bolt carried by a reciprocable
bolt carrier assembly. Usually the bolt is movable over a predetermined
distance with respect to the bolt carrier assembly.
So that the bolt/bolt carrier assembly may be driven rearwardly to compress
the main drive spring the bolt carrier assembly is extended forwardly
longitudinally with the barrel to the region of the normally provided
barrel gas port which is connected to a cylinder containing a piston
arranged to contact and provide rearward impetus to the bolt carrier
assembly.
Advantageously, the main drive spring is mounted on a guide means which is
located forwardly adjacent said cylinder and rearwardly adjacent the
receiver rear wall and, preferably, the rearward location of the guide
means is on the interior of the rear receiver wall, the exterior rear
receiver wall being in abutting relationship with a buttstock.
The terms "forward" and "rearward" and similar adverbial phrases used
herein are used in relation to the gun muzzle so that, for example, the
buttstock is positioned rearwardly of the muzzle.
The invention will now be described, by way of example, with reference to
the accompanying drawings, in which:
FIG. 1 shows a longitudinal cross-sectional view of a gas operated, fully
automatic, gun in accordance with this invention,
FIGS. 2A and 2B show the maximum and minimum feed overtravel in known gas
operated guns,
FIGS. 3A and 3B show the maximum and minimum feed overtravel in the present
gun,
FIGS. 4A and 4B show the effects of differing amounts of energy from a
cartridge on a known gas operated gun,
FIGS. 5A and 5B show, in comparison to FIGS. 4A and 4B, the effects of
differing amounts of energy from a cartridge on the present invention in
said one aspect,
FIGS. 6A-6E show schematically the operation and impulse forces on a gun in
accordance with the further aspect of the invention firing from an open
bolt position,
FIGS. 7A-7E show graphs representative of the reaction/counter-reaction
forces of the gun shown in FIGS. 6A-6E respectively.
FIGS. 8A and 8B respectively show, in schematic and graphical form, the
operation of a known gas operated gun firing from the open bolt position,
FIG. 9 shows a graph of the reaction presented to a user of the gun in
accordance with the further aspect of this invention, and
FIG. 10 shows a comparative graph to FIG. 5 demonstrating the reaction
presented to a user of a known gas operated gun.
In the Figures like reference numerals denote like parts.
The gas operated automatic gun shown in FIG. 1 has a receiver 1 to the rear
wall 100 of which is connected a buttstock 2 and at the opposite end of
the receiver 1 from the buttstock 2 there is connected a barrel 10. A
pistol grip 11 is connected by a screw and nut underneath the receiver 1
and a fore grip 12 is connected on the underside of the barrel 10. The
pistol grip 11 is connected to the receiver 1 through the intermediary of
a trigger guard 72 shrouding a trigger assembly 73 having an arcuate
finger pull trigger 730 pivotably mounted on a rod 731, the trigger 730
being biassed by a spring 732 acting in a blind hole within the trigger
with one end of the spring against the inside of the blind hole and the
other end of the spring against a trigger spring retainer 733 which is
stationary with respect to the receiver. The retainer 733 is located in a
guide slot 734 in the trigger 730. A top rear face 735 of the trigger 730
acts against the conventionally supplied sear assembly 7 having a sear 700
pivotally mounted on a transverse rod 701 which passes through into
opposing side walls of the receiver. The sear 700 is biassed into a
non-firing position by a compression spring 702 located between a recess
703 in the sear 700 and a stud 704 mounted on the base of the receiver.
A bolt carrier assembly 3 is slidably mounted upon a rail 101 in the
receiver and the bolt carrier assembly comprises a block 300 which is
suitably shaped to contact with the rail 101 and in which is secured
vertical (as shown in FIG. 1) sear locking lugs 325, one on each side of
the gun longitudinal axis (only one of which is shown in the section view
of FIG. 1). Secured, for example, by welding to the top of the block 300
is a "P" cross-sectionally shaped sheet member 301 with the upright of the
"P" being horizontally disposed so the "P", as it were, lies on its back.
Inside the wrapped over, enclosed, portion of the "P" is a spring biassed
antibounce weight (not shown) and longitudinally disposed adjacent to the
non-enclosed portion of the "P" is a main drive spring assembly 302. For
ease of explanation, it should here be stated that the main drive spring
assembly 302 has been shown as if it were on the axial centre line of the
gun but, in practice, the assembly 302 is offset to the right of the
centre line when viewed forwardly. The main drive spring assembly 302 has
a guide rod 303 of circular cross-section having end portions 304, 305
respectively, the part between the end portions 304, 305 being provided
with parallel flats 306. Mounted over the guide rod 303 is a main drive
spring 307. At the end of the P shaped member 301, remote from the block
300, is a bush 308 having a recess 309 into which the spring 307 is
located and a circular cross-sectioned recess 310 to slidingly accept the
end 304 of the guide rod 303. At the remote end of the main drive spring
307 from the bush 308 is a collar 311 which is secured to the guide rod
303 by a cross pin 312; the purpose of the collar 311 being to provide an
end retainer for the spring 307 and to support the rear end of the guide
rod 303 on a lug 102 on the receiver rear wall 100. The cross pin 312
extends through a slot in the side wall of the receiver and, hence,
prevents the rear wall 100, which is slidably mounted, dropping unless the
collar 311 is removed from the lug 102 by sliding the cross pin 312
forwardly.
Mounted on the longitudinal axis of the barrel and inside the block 300 is
a firing pin 313 which is biassed in a rearward position by a compression
spring 314 with the limits of travel of the firing pin being maintained by
a slot 315 in the firing pin co-operating with a cross pin 316, the spring
314 and pin 316 being provided essentially for removal of the firing pin.
Encompassing the front portion of the firing pin is a bolt 317 which is
slidingly rotatable on the longitudinal axis of the barrel inside the
block 300 and is, thus, movable relative to the carrier assembly. The bolt
317 is conventionally provided with a cam pin 318, which pin 318
co-operates in known manner with a cam slot (not shown) in the block 300.
Further, the bolt 317 is provided in conventional manner with an ejector
pin 319 which is offset to the left (looking forwardly) of the barrel
longitudinal axis and which pin is forwardly biassed by a coil spring 320,
the forward extent of travel of the pin 319 being limited by a stop 321
acting in a slot in the pin 319. The bolt 317 also has a spring biassed
claw (not shown since it is positioned on the right of the longitudinal
centre line looking forwardly) which, in operation, engages the cannelore
of a ca | | |
