Automated projectile firing weapon and related method

BACKGROUND OF THE INVENTION

The present invention relates generally to automatic projectile firing weapons. More particularly, the invention relates to a method and apparatus for absorbing the recoil force of an automatic projectile firing weapon.

In many combat situations, a lightweight, easily portable automatic weapon that is capable of accurately firing a projectile over a significant distance would provide a decisive tactical advantage. There are many existing small and medium caliber automatic weapons that are specifically designed to fill particular combat needs. However, weapons that are effective at ranges of up to 2,000 meters, for example the 0.50 caliber M2 heavy machine gun and the 40 mm Mk-19 grenade, are too bulky and heavy to be easily portable. Other automatic weapons, like the 7.62mm M60/M240 medium machine guns and the 5.56 mm M249 squad automatic weapon, are easily portable but are not effective at long ranges.

The accuracy of a weapon at a long range is dependent upon the ability of the weapon to manage the recoil force of the fired projectile. The magnitude of the recoil force is a function of the mass and velocity of the projectile which directly effects the expected travel distance (range) of the fired projectile. As the expected range of the weapon increases, so does the magnitude of the recoil force. Weapons designed to fire projectiles over a significant distance typically have a greater weight than weapons designed to fire projectiles over a shorter range. The greater weight is necessary to restrain the more energetic cartridges, absorb the increased recoil force, and prevent the recoil force from disrupting the accuracy of the weapon.

To reduce the weight of a weapon that is accurate over a significant range, an improved method of handling the recoil force must be found. Many attempts have been made to manage the recoil force beyond the typical short recoil cycle or gas operated bolt cycle. In some designs, a counterweight is attached to the recoiling mass of the weapon to absorb the recoil energy. In other designs, a spring is used to absorb and store the recoil force. The energy stored in the spring or counterweight can then be used to move the recoiling mass forward when the next projectile is fired. The forward momentum of the counter-recoiling mass will partially absorb the recoil force of the next projectile.

However, these designs fail to account for the recoil force resulting from the first projectile. Because the first projectile is fired when the weapon is in a resting state, the only resistance to the initial recoil force is the spring or counterweight. This results in a higher load on the recoil system when the first projectile is fired as compared to subsequent shots. In a tripod mounted weapon, this higher load lifts the front leg of the tripod higher off the ground, which will disrupt the accuracy of at least the first few projectiles of a burst. The higher load also causes instability in the gun/mount system, which may only be corrected by increasing the amount of ballast in the system.

After a transient period, the weapon and mount will overcome the recoil overload and achieve a steady state dynamic recoil action. If the weapon is flexibly mounted, it is likely the weapon will not become accurate and effective until the transient period is passed and the weapon enters this steady state recoil action. However, during the transient period, several projectiles are wasted before the weapon settles into the steady state recoil action. Furthermore, due to mount flexibility, a steady state recoil action can have significant effects on accuracy.

In light of the foregoing there is a need for an automatic weapon that minimizes the effect of the recoil force of both the initially fired rounds and all subsequent rounds.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an automatic projectile firing weapon that obviates one or more of the limitations and disadvantages of prior art automatic projectile firing weapons. The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purposes of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims.

To attain the advantages and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention is directed to an automatic projectile firing weapon. The weapon includes a receiver that has a main sear and a trackway. A barrel assembly is slidably mounted in the trackway and is moveable between a rearward position and a forward position. The barrel assembly is engageable with the main sear at the rearward position. A firing position is located between the rearward position and the forward position and preferably closer to the forward position. There is provided an operating spring connected between the receiver and the barrel assembly. The operating spring biases the barrel assembly towards the forward position. There is also provided a manual retracting device that moves the barrel assembly rearwardly into engagement with the main sear, thereby compressing the operating spring. A trigger is provided to release the main sear and allow the operating spring to move the barrel assembly forwardly along the trackway of the receiver. There is further provided a buffer connected between the receiver and the barrel assembly to dampen the velocity of the barrel assembly to prevent the barrel assembly from exceeding a predetermined maximum velocity when a round is fired. The recoil energy from the fired round is absorbed in part by the forward motion of the barrel assembly and in part by the operating spring. The recoil force felt by the receiver is that of the operating spring and, in part, the buffer.

In another aspect, the invention is directed to a method of absorbing the recoil force of a projectile firing weapon. The weapon includes a barrel assembly slidably mounted in a receiver and an operating spring connected between the receiver and the barrel assembly. The method involves compressing the operating spring by retracting the barrel assembly within the receiver to engage the barrel assembly with a main sear when the operating spring is fully compressed. The main sear is released to allow the operating spring to bias the barrel assembly forwardly within the receiver. A round is chambered as the barrel assembly moves forwardly along the trackways. The forward motion of the barrel assembly is buffered to prevent the barrel assembly from exceeding a predetermined maximum velocity. The round is fired when the barrel assembly reaches a predetermined location in the receiver. The recoil force of the fired shot reverses the motion of the barrel assembly to move the barrel assembly rearward and re-compress the operating spring. The buffer is configured to maintain a nearly constant dynamic condition of the barrel assembly during the firing and recoil portions of the operating cycle so that effects of varying friction, weapon attitude, and cartridge impulse on the weapon operating cycle are minimized.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and together with the description, serve to explain the principles of the invention. In the drawings,

FIG. 1

is a perspective view of an automatic projectile firing weapon according to the present invention;

FIG. 2

is a partial perspective cut-away view of the automatic projectile firing weapon of the present invention;

FIG. 3

is a perspective view of a receiver according to the present invention;

FIG. 3

a

is a partial perspective view of the receiver of

FIG. 3

, illustrating a cocking lever trip;

FIG. 4

is a perspective cut-away view of a barrel assembly according to the present invention;

FIG. 5

is an exploded view of a bolt assembly of the automatic projectile firing weapon of the present invention;

FIG. 6

is a perspective view of a retracting device and a rear portion of the barrel assembly and the bolt carriage according to the present invention;

FIG. 7

is a perspective view of the retracting device and bolt carriage of

FIG. 6

;

FIG. 8

is a perspective cut-away view of the rear portion of the weapon of the present invention, illustrating the engagement of the barrel assembly with the main sear;

FIG. 9

is a perspective view of a buffer according to the present invention;

FIG. 10

is a cross-sectional view of the buffer of

FIG. 9

;

FIG. 11

is a side cross-sectional view of the weapon of the present invention, illustrating the pre-charged state where the operating spring and bolt springs are expanded;

FIG. 12

is a side cross-sectional view of the weapon of the present invention, illustrating the charged state where the operating spring and bolt spring are compressed;

FIG. 13

is a side cross-sectional view of the weapon of the present invention, illustrating the expansion of the operating spring and a round being stripped and rammed;

FIG. 14

is a side cross-sectional view of the weapon of the present invention, illustrating the firing position;

FIG. 15

is a side cross-sectional view of the weapon of the present invention, illustrating the mid-recoil position of the barrel assembly; and

FIG. 16

a side cross-sectional view of the weapon of the present invention, illustrating the maximum recoil position of the barrel assembly.

DETAILED DESCRIPTION

Reference will now be made in detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

In accordance with the present invention, an automatic projectile firing weapon is provided. The exemplary embodiment of the weapon of the present invention is a lightweight automatic crew served weapon for firing medium caliber munitions. The present invention contemplates, however, that the principles and methods disclosed herein are applicable to automatic weapons of all sizes. The exemplary embodiment of the automatic projectile firing weapon of the present invention is shown in FIG.

1

and is designated generally by the reference number

20

.

As illustrated in

FIG. 1

, weapon

20

includes a receiver

22

, a mount

26

, and a pair of handles

30

that are attached to receiver

22

. Mount

26

allows weapon

20

to be pivoted horizontally (traverse) and vertically (elevation) to provide a full range of firing directions. Handles

30

can be manipulated to horizontally or vertically pivot the weapon about mount

26

to adjust the aim of weapon

20

.

Mount

26

connects receiver

22

to a flexible structure. In the exemplary embodiment, weapon

20

is mounted on a tripod

28

. The present invention contemplates, however, that weapon

20

may be mounted on any other flexible structure readily apparent to one skilled in the art, such as, for example, a moving vehicle.

Preferably, the weapon

20

also includes a targeting device

36

. Targeting device

36

may include direct view optics and a laser targeting system or any other range finding instrument readily apparent to one skilled in the art. In addition, targeting device

36

may also include a display screen to display information from the laser targeting system or other information regarding firing status of the weapon. As illustrated in

FIG. 2

, each of the pair of handles

30

may include a set of buttons

56

. Buttons

56

may be used to activate the laser targeting system or perform any standard operating function of targeting device

36

.

In accordance with the present invention, the weapon includes a barrel assembly that is slidably mounted within the receiver. The barrel assembly is moveable between a rearward position and a forward position and has a firing position between the rearward and forward positions. An operating spring is connected between the receiver and the barrel assembly. The operating spring biases the barrel assembly forwardly within the receiver. In the disclosed embodiment, the barrel assembly is slidably mounted on a trackway in the receiver. The present invention contemplates that other types of mountings will be readily apparent to one skilled in the art.

As embodied herein and illustrated in

FIG. 1

, weapon

20

includes a receiver

22

. A barrel assembly

34

is contained within the receiver

22

. As illustrated in

FIG. 2

, an operating spring

44

is disposed on a guide

46

. Operating spring

44

is connected between receiver

22

and barrel assembly

34

so that a rearward movement of barrel assembly

34

operates to compress operating spring

44

. A buffer (not shown) is also connected between the barrel assembly

34

and the receiver

22

.

As illustrated in

FIG. 3

, receiver

22

includes an operating spring compartment

72

, a buffer compartment

74

, and tracks

70

. Operating spring

44

and guide

46

are positioned within operating spring compartment

72

of receiver

22

. Barrel assembly

34

includes trackways

84

(referring to

FIG. 6

) that correspond to and engage tracks

70

. This engagement is configured to allow barrel assembly

34

to slide within receiver

22

between a forward and a rearward position.

As illustrated in

FIG. 3

, receiver

22

also includes an ammunition feed opening

76

,

77

on either side of weapon

20

. In the preferred embodiment, an ammunition can

24

(referring to

FIG. 1

) is mounted, on either side of the weapon, adjacent either ammunition feed opening

76

,

77

on receiver

22

to provide ammunition to weapon

20

. Ammunition can

24

is positioned external to receiver

22

, on either side of the weapon, to allow easy removal and replacement during operation of the weapon.

The ammunition may be fed to the weapon by any means readily apparent to one skilled in the art. In the embodiment illustrated in

FIG. 2

, an ammunition feed sprocket

54

is provided within receiver

22

to advance the ammunition through the weapon. Feed sprocket

54

moves the ammunition from ammunition can

24

to a strip position adjacent and above the barrel assembly

34

.

As illustrated in

FIG. 3

a

, receiver

22

also includes a cocking lever trip

79

. Cocking lever trip

79

is located in a fixed position toward the front end of receiver

22

along tracks

70

.

As illustrated in

FIG. 4

, barrel assembly

34

includes a barrel

52

, a barrel extension

60

and a bolt assembly

42

. Barrel

52

includes a chamber

88

and breech locking lugs

89

. Barrel extension

60

extends rearward from barrel

52

and defines a track

112

. Bolt assembly

42

is slidably positioned in track

112

. Preferably, the sliding motion of bolt assembly

42

is limited on the forward end by chamber

88

and on the rearward end by a bolt bumper

86

.

As illustrated in

FIG. 5

, bolt assembly

42

includes a bolt carriage

92

, a gas shutoff valve

94

, a bolt body

96

, and a bolt spring (not shown) disposed within bolt carriage

92

. As illustrated in

FIG. 4

, bolt carriage

92

is slidably disposed within a gas cylinder

82

of barrel assembly

34

. In this embodiment, the gas cylinder

82

is an integral part of barrel extension

60

. The bolt spring acts on bolt carriage

92

to move bolt carriage

92

forwardly within track

112

and gas cylinder

82

of barrel extension

60

. Bolt assembly is engageable with a bolt sear (not shown) to hold the bolt assembly rearward and hold the bolt spring in a compressed condition.

Referring again to

FIG. 5

, bolt carriage

92

includes an opening

108

to receive bolt body

96

that includes a spring operated rammer

93

. Rammer

93

strips a round of ammunition from the ammunition feed belt and feed sprocket

54

as operating spring

44

(referring to

FIG. 2

) urges barrel assembly

34

forwardly within barrel extension

60

. The bolt spring urges bolt assembly

42

forwardly until the stripped round is rammed and locked into chamber

88

.

The bolt

96

is stopped when the round is chambered. The bolt carriage

92

, however, will continue forward, urged by the bolt spring. Bolt assembly

42

includes a cam pin

90

that engages bolt body

96

and a cam surface

91

in bolt carriage

92

. As bolt carriage

92

moves forward, cam pin

90

rides along cam surface

91

to convert the linear motion of bolt carriage

92

into a rotary motion of bolt body

96

, to engage the bolt body lugs with barrel lugs

89

(referring to FIG.

4

). A carriage buffer

102

removes any excess energy of the bolt carriage.

As shown in

FIG. 5

, bolt body

96

includes an internal opening

106

, which houses a firing pin

98

, a firing spring

100

, and a spring seat/carriage buffer

102

. The final portion of bolt ram is utilized to charge firing spring

100

into cocked position. Firing spring

100

is released when cocking lever

99

contacts cocking lever trip

79

(referring to

FIG. 3

a

) mounted in the receiver

22

. Firing spring

100

urges firing pin

98

into contact with the round. The force of the contact between firing pin

98

and the percussion primer causes the cartridge to fire. Propellant gas from the fired round is directed into gas cylinder

82

through gas port

83

(referring to FIG.

4

). The propellant gas contacts the gas piston of carriage and gas shutoff valve

94

and causes bolt assembly

42

to move rearwardly in track

112

.

Preferably, a muzzle device

32

is affixed to the muzzle end of barrel

52

. Muzzle device

32

may house muzzle velocity correction components. Muzzle device

32

also operates to shield muzzle gas, hide muzzle flash, and act as a muzzle brake, which reduces net impulse delivered to the weapon.

In accordance with the present invention, a manual retracting device is provided. The retracting device is configured to engage the barrel assembly, prior to firing, to move the bolt assembly rearwardly into engagement with the bolt sear and to move the barrel assembly rearwardly within the receiver and into engagement with the main sear. In the exemplary embodiment, the retracting device includes a pawl that is engageable with the bolt assembly to retract the barrel assembly. It is contemplated that alternative devices for retracting the barrel assembly will be readily apparent to one skilled in the art.

As illustrated in

FIG. 6

, a manual retracting device

110

is positioned alongside the rear portion of barrel assembly

34

. Retracting device

110

includes a handle

40

and a guide tube

114

. Handle

40

is connected to a cable

116

that is disposed in guide tube

114

(referring to FIG.

7

).

As shown in

FIG. 7

, a pawl

122

and pawl carriage

120

are connected to the end of cable

116

opposite handle

40

. A return spring

118

is disposed around cable

116

between handle

40

and pawl carriage

120

. Pawl

122

pivots about a pin

128

in pawl carriage

120

. Pawl

122

is spring loaded out and configured to engage a slot

124

in bolt carriage

92

.

If the weapon is uncharged and handle

40

is pulled from its stowed position, pawl

122

engages slot

124

and moves bolt carriage

92

rearwardly along track

112

in barrel extension

60

. Bolt carriage

92

moves rearwardly, compressing the bolt spring until bolt assembly

42

engages bolt bumper

56

and the bolt sear (not shown). The continuing rearward motion of handle

40

and pawl

122

then causes the entire barrel assembly

34

to move rearwardly within receiver

22

. The rearward motion of barrel assembly

34

compresses operating spring

44

and continues until barrel assembly

34

engages main sear

In the exemplary embodiment, bolt carriage has a second slot

126

. In this embodiment, the handle must be retracted twice (equivalent to two half strokes) to move the barrel assembly into engagement with the main sear. When handle

40

is released after the first half stroke, which locks the bolt assembly

42

with the bolt sear, the return spring

118

of the retracting device

110

urges pawl carriage

120

forwardly within guide tube

114

. Spring loaded pawl

122

pivots inwardly and rides along the surface of bolt carriage

92

until pawl

122

reaches second slot

126

. Handle

40

is then retracted a second half stroke to engage barrel assembly

34

with main sear

130

.

As illustrated in

FIG. 8

, barrel assembly

34

includes a sear lug

131

on the carriage that engages main sear

130

at the fully rearward position. Main sear

130

is mounted on a trigger shaft

134

within the back cover portion of receiver

22

. Triggers

38

are connected to trigger shaft

134

. Depressing either or both of triggers

38

causes trigger shaft

134

to rotate. The rotation of trigger shaft

134

disengages main sear

130

from barrel assembly

34

and allows operating spring

44

to move the barrel assembly forward and initiate the firing sequence.

Preferably, receiver

22

also includes a semi-automatic sear

132

. Semi-automatic sear

132

is also engageable with barrel assembly

34

. Semi-automatic sear

132

may also be mounted on trigger shaft

134

such that if the selector is in the semi-automatic mode, a depression of either or both triggers

38

will cause semi-automatic sear

132

to maintain engagement with barrel assembly

34

after the first shot. When the weapon is operating in semi-automatic mode, semi-automatic sear

132

will engage barrel assembly

34

after each round is fired, even when the trigger is depressed.

In accordance with the present invention, a buffer is connected between the receiver and the barrel assembly. The buffer dampens the movement of the barrel assembly to prevent the barrel assembly from exceeding a predetermined maximum velocity when a round is fired. During the initial portion of the recoil stroke, the buffer maintains a nearly constant force, the magnitude of which is governed by the initial recoil velocity of the barrel assembly, through the rearward travel of the barrel assembly, thereby mitigating the recoil load. The disclosed buffer utilizes a damping fluid and shuttle valves to govern the motion of the barrel assembly, although it is contemplated that other alternatives will be readily apparent to one skilled in the art.

As illustrated in

FIG. 9

, a buffer

140

is provided having a housing

146

and a piston rod

142

. A first connecting device

144

is positioned on one end of piston rod

142

and a second connecting device

148

is positioned on one end of housing

146

. Buffer

140

is positioned within a buffer compartment

74

of receiver

22

(referring to FIG.

3

). Connecting device

144

connects piston rod

142

to barrel assembly

34

. Connecting device

148

connects housing

146

to receiver

22

. Movement of barrel assembly

34

relative to receiver

22

results in a corresponding movement of piston rod

142

relative to housing

146

.

As shown in

FIG. 10

, buffer

140

includes a reserve

150

of damping fluid, a stationary sleeve

156

, and a moving sleeve

158

. Stationary sleeve

156

is fixed within housing

146

and moving sleeve

158

is slidably disposed within stationary sleeve

156

. A valve spring

160

is positioned on each side of moving sleeve

158

to center moving sleeve

158

within housing

146

.

A piston

152

is connected to piston rod

142

and is slidably disposed within moving sleeve

158

. Preferably, a seal

154

is disposed around piston

152

to prevent damping fluid from flowing between piston

152

and moving sleeve

158

. In addition, a seal

162

is positioned at opening

166

in moving sleeve

158

through which piston rod

142

passes.

The stationary sleeve

156

includes a plurality of buffering orifices

164

. The moving sleeve

158

includes a corresponding plurality of buffering orifices

166

and a plurality of larger valve orifices

166

. The buffering orifices

166

on moving sleeve

158

are offset from the buffering orifices

164

on stationary sleeve

156

.

When piston

152

slides within moving sleeve

158

in response to a corresponding movement of barrel assembly

34

, piston

152

forces fluid through valve orifices

168

and

169

and into reserve

150

. Valve orifices

168

are large enough that there is little resistance to the movement of piston

152

when the piston is moving at a low velocity. However, as the velocity of piston

152

increases and the rate of flow of fluid through valve orifices

168

increases, the resistance encountered by piston

152

also increases. The increased resistance encountered by piston

152

is opposed by the force of valve spring

160

acting on moving sleeve

158

. When the piston reaches a certain velocity, the force exerted by piston

152

on moving sleeve

158

overcomes the force of valve spring

160

and causes moving sleeve

158

to slide within stationary sleeve

156

.

The movement of the moving sleeve

158

within the stationary sleeve

156

moves the valve orifices

168

and

169

out of alignment and causes buffering orifices

164

and

166

to align. Because buffering orifices

164

and

166

are smaller than valve orifices

168

and

169

, moving piston

152

encounters a greater resistance in forcing fluid through buffering orifices

164

into reserve

150

. This increased resistance on piston

152

causes a decrease in piston

152

velocity. As the velocity of piston

152

decreases so does the force exerted on moving sleeve

158

. When the velocity of piston

152

decreases below a certain velocity, the force of valve spring

160

moves moving sleeve

158

within stationary sleeve

156

to re-align valve orifices

164

and

166

. In this manner, buffer

140

operates to prevent the velocity of piston

152

and connected barrel assembly

34

from exceeding a predetermined maximum velocity.

Preferably, moving sleeve

158

and stationary sleeve

156

have a second set of buffering orifices

153

and

155

, respectively. The second set of buffering orifices are positioned such that the velocity of movement of piston

152

in the opposite direction may also be prevented from exceeding a predetermined maximum velocity. In this manner, buffer

140

can govern the velocity of movement of barrel assembly

34

in both directions.

The operation of the aforementioned device will now be described with reference to the attached drawings.

The operation of the automatic projectile weapon of the present invention begins with weapon

20

in the un-charged position as illustrated in FIG.

11

. The barrel assembly

34

is in the forward position. The operating spring

44

and bolt spring

95

are at their extended lengths and minimum pre-loads. The bolt assembly

42

is in its forward and locked position within the barrel extension

60

. The ready round

170

(the next round to be fired) is within the ammunition feed sprocket

54

.

The handle

40

of retracting device

110

is then pulled to charge weapon

20

. As illustrated in

FIG. 12

, the charging stroke compresses bolt spring

95

and operating spring

44

. In an alternative embodiment, handle

40

is pulled twice to fully compress the bolt spring and operating spring

44

in sequence.

In the charged position, bolt assembly

42

is latched rearward within the barrel extension

60

by the bolt sear and the barrel extension

60

is latched rearward within receiver

22

by the main sear

130

(referring to FIG.

8

). Feeder sprocket

54

advances ready round

170

into the strip position in front of bolt assembly

42

. As result of the aftward motion of the barrel extension, the feed sprocket advances one pocket position. Specifically, the cam follower on top of the barrel extension, via engagement with the feed cam, causes approximately 60° rotation of the 6 tooth sprocket with a 6″ stroke of barrel extension. The feed cam drives the feed sprocket via a cam pawl. The feed sprocket is retained in the indexed position with a sprocket pawl. Upon forward stroke of the barrel extension (at the beginning of the firing cycle), the feed cam rotates back

600

, which moves the cam pawl back one pocket or position. The weapon is now ready to fire.

An optional procedure for preparation of the weapon for firing is to charge the weapon as described above, but without ammunition or unloaded. With the weapon charged, the ammunition belt is introduced into the feed port and the sprocket is manually indexed to position the first cartridge at the belt strip position. This is accomplished simply by overriding the sprocket pawl.

Depressing trigger

38

releases the entire barrel assembly

34

from main sear

130

, thereby allowing operating spring

44

to move barrel assembly

34

forward within the receiver

22

. As barrel assembly

34

moves forward in receiver

22

, bolt assembly

42

, via the spring loaded rammer, strips ready round

170

from feed sprocket

54

.

Following the ammunition strip, the bolt sear releases bolt carriage

92

, allowing the bolt spring to move bolt carriage

92

forwardly within barrel assembly

34

, while the barrel assembly continues to move forward relative to receiver

22

. As illustrated in

FIG. 13

, a fixed guide

172

within receiver

22

directs ready round

170

toward the centerline of barrel

52

. Round

170

is further guided into chamber

88

by fixed guides within the barrel extension

60

.

As illustrated in

FIG. 14

, the full expansion of the bolt spring causes bolt assembly

42

to lock round

170

in chamber

88

. This is accomplished by the final portion of the longitudinal stroke of the carriage causing rotation of the bolt behind the chambered cartridge. The bolt is interconnected to the carriage via a lock pin

90

(referring to

FIG. 5

) through the bolt which engages lock cam way

91

of the carriage. The lock rotation (of approximately 54° in this embodiment) is driven by the carriage longitudinal stroke (of approximately 0.85″) The forward velocity of barrel assembly

34

is governed by buffer

140

to ensure the barrel assembly does not exceed a predetermined maximum velocity. Upon reaching a fixed position in receiver

22

, firing pin spring

100

is released to urge firing pin

98

into contact with round

170

. The contact results in round

170

being fired.

Propellant gas from the fired round accelerates the projectile through barrel

52

. When the accelerating projectile passes a gas port in barrel

52

, bleed gas is directed through gas port

83

into gas chamber

82

to move bolt assembly

42

rearwardly in barrel extension

60

accomplishing unlock of the bolt and extraction of the spent casing from the chamber. As illustrated in

FIG. 15

, the spent casing

174

is ejected from the bolt face as another round

176

is advanced by feed sprocket

54

. Bolt assembly

42

moves rearwardly within barrel extension

60

to compress the bolt spring and re-engage the bolt sear.

Part of the recoil impulse of the fired round cancels the forward momentum of the barrel assembly

34

. After this deceleration, the remainder of the recoil impulse accelerates the barrel assembly

34

rearwardly along the recoil stroke within receiver

22

. The maximum forward velocity of barrel assembly

34

allowed by buffer

140

is chosen to ensure that the forward momentum of the barrel assembly is not great enough to cancel the recoil impulse of the round and that the remainder of the recoil impulse is great enough to move barrel assembly

34

to the rearward position. The maximum rearward velocity of barrel assembly

34

allowed by buffer

140

is chosen to accomplish the feed index function, recompress the main spring, and to prevent the barrel assembly from moving too far rearwardly within receiver

22

. Thus, if barrel

52

of weapon

20

is angled upwardly such that gravity increases the recoiling force of the barrel assembly, buffer

140

will trim the rearward velocity to prevent the barrel assembly from exceeding the predetermined maximum.

When barrel assembly

34

reaches the rearward position illustrated in

FIG. 16

, operating spring

44

is fully compressed. Feeder sprocket

54

has advanced the next round to be fired

176

into the strip position. In the automatic mode, with trigger remaining depressed, operating spring

44

overcomes the rearward momentum of the barrel assembly

34

and the barrel assembly

34

begins to accelerate forwardly within receiver

22

and the firing sequence is repeated. If in the auto mode, and the trigger has been released prior to this point in the cycle, the main sear will engage the barrel assembly to arrest motion and to stop firing.

If the weapon is operating in the semi-automatic firing mode, barrel assembly

34

engages semi-automatic sear

132

at the rearward position. Depression of trigger

38

releases barrel assembly

34

and the firing sequence is repeated.

Thus, the automatic projectile firing weapon of the present invention provides a recoil device that allows the weapon to achieve a steady state dynamic recoil action on the first shot and every shot thereafter. This recoil device minimizes the deleterious effects of conventional gun recoil on light-weight weapon system accuracy. The natural firing rate of the barrel assembly and the gas operation of the bolt further reduce the transmission of recoil forces to the receiver. This reduction of recoil force permits a lightweight weapon and mount configuration, while retaining dynamic stability. The lightweight configuration enhances weapon system capabilities in transport, deployment and field operation.

It will be apparent to those skilled in the art that various modifications and variations can be made in the method of manufacture of the present invention and in construction of this automatic projectile firing weapon without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.