US3724325A

US3724325A - Rate reducer

Info

Publication number: US3724325A
Application number: US00174334A
Authority: US
Inventors: S Silsby
Original assignee: COLTS IND OPERATING CORP
Current assignee: CFPI Inc A CORP OF; COLT LICENSING A DE Ltd PARTNERSHIP LP; COLTS IND OPERATING CORP; COLTS IND OPERATING CORP US; CII Holdings Inc
Priority date: 1971-08-24
Filing date: 1971-08-24
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

An automatic firearm incorporates an integral rate reduction device which delays hammer fall. The rate reduction device is associated with an automatic sear and includes an inertia mass adapted to be pivoted by the hammer during initial hammer fall. In semiautomatic operation, the inertia mass is not displaced by the hammer when it is pivoted between a cocked position and the fired position, since all rate reducer action is completed before a shooter pulls the trigger.

Description

11] 3,724,325 Apr. 3, 1973 nited States Patent {191 Silsby 2 459 158 1/1949 Garand...................................89/l3l 2,215,470 9/1940 Johnson [54] RATE REDUCER [75] Inventor: Stanley D. Silsby, Granby, Mass.

[73] Assignee: Colts Industries Operating Corp., P i E i er-Stephen C. Bentley fi York, NY Attorney-Radford W. Luther ABSTRACT An automatic firearm incorporates an integral rate reduction device which delays hammer fall. The rate N .mL

[52] US. Cl......,..................89/l31, 42/1 S, 42/75 C, reduction device is associated with an automatic sear 1m Cl 89/142 a g and includes an inertia mass adapted to be pivoted by 89/129, 131,149,154 the hammer during llll la hammer a In semrauto [58] Field of Search........

matic operation, the inertia mass is not displaced by the hammer when it is pivoted between a cocked posi- [56] References C'ted tion and the fired position, since all rate reducer ac- UNITED STATES PATENTS tion is completed before a shooter pulls the trigger.

3,129,637 4/1964 Packard 9 Claims, 11 Drawing Figures PATENTEUAPRS I975 3.724;.325

SHEU 1 BF 4 PATENTEDAPRB I975 SHEET 2 [1F 4 PATENTEUAPR3 I975 SHEET 3 0H1 RATE REDUCER BACKGROUND OF THE INVENTION The invention relates to automatic firearms and more particularly to automatic firearms which incorporate a means to reduce the rate of fire in automatic operation.

Arrangements which serve to reduce the rate of fire during automatic operation are known in the prior art. An example of such a mechanism is shown in U.S. Pat. No. 3,30l,133 issued to F. E. Sturtevant. While the mechanism as shown in this patent yields eminently satisfactory operation, it occupies space in an area which does not exist in all weapons.

SUMMARY OF THE INVENTION The invention contemplates the use of a rate reduction device which incorporates a pivotally mounted inertia mass. Cooperating means on the hammer and the mass act to rotate the inertia mass during initial hammer fall, thereby delaying hammer fall during automatic operation. An automatic sear engages the inertia mass to prevent its displacement by the hammer until the bolt is completely locked. This arrangement effectively reduces the rate of fire to an acceptable value and does not require excessive space in the receiver of the firearm. Moreover, a rate reducer according to the invention requires a minimum number of components.

Accordingly, it is a primary object of the invention to provide a firearm including means capable of automatically retarding the rate of fire or speed at which the firearm is discharged during automatic operation.

Another object of the invention is to provide an automatic firearm possessing a delayed automatic firing feature which does not necessitate the provision of excessive space in the receiver.

A further object of the invention is to provide a firearm including a rate of fire reducer for automatic operation which is associated with an automatic sear.

A still further object of the invention is to provide a firearm having a rate reducer for automatic operation which does not impair the accuracy of the firearm during semiautomatic operation.

Other objects and advantages of the invention will become apparent of the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a firearm incorporating a rate reducer according to the invention.

FIG. -2 is an isometric cutaway view of the firearm of DETAILED DESCRIPTION OF PREFERRED EMBODIMENT turning now to the drawings in detail, there is shown in FIG. 1 an automatic, gas-operated firearm 12. The

firearm 12 includes a receiver section generally shown at 14 having an upper receiver 14a and a lower receiver 14b. A magazine 16 is partially contained within the receiver section 14 for delivering cartridges thereto. Connected to the upper receiver is a barrel 18. A trigger 22 is disposed forwardly of a hand grip 24. The trigger 22 is mounted upon the barrel 18 for axial movement parallel to the axis of the barrel and rotational movement thereabout. Secured above the barrel 18 is a gas tube 26 which contains the piston for successively cycling the operating components and cocking the firing mechanism during automatic and semiautomatic operation. At the front and rear ends of the firearm are respectively located

sight assemblies

28 and 30. The three post sights, which constitute the front assembly, are threadably secured to the firearm in front of the tube 26 for vertical adjustment to obtain the proper elevation when zeroing in the firearm. The rear sight 30 comprises three peeps, each adapted to be used with a corresponding post on the front sight as sembly 28 in accordance with the selected pistol grip position.

Turning now to FIG. 2, the construction of the firearm 12 may be better appreciated. As shown in FIG. 2, the barrel 18 comprises a chamber 32 adapted to receive a cartridge inserted therein by a bolt assembly 33. When a cartridge chambered in chamber 32 is fired during either automatic or semiautomatic operation, the bullet travels outward through the bore of the barrel 18 under the impetus of the expanding gases. Some of these gases are diverted through the gas port 36, formed in the barrel 18 into a chamber 38, defined by the gas tube 26 and a piston 39 attached to the forward end of an operating rod 40, the rod 40 being disposed within the tube 26 for axial movement therein. Secured to the barrel 18 is a spring stop 42 which serves as a spring seat for an operating spring 44 which is coiled around the operating rod 40. Hence, the gas pressure generated within the chamber 38 by the expanding gases drives the operating rod 40 rearwardly, against the bias of the operating spring 44, to cycle the operating components and the firing mechanism in a manner explained hereinafter. A depending abutment 48, carried by the operating rod 40, engages the bolt carrier 50 of the bolt assembly 33 so as to impart reciprocating movement thereto within the upper receiver 14a. The operating rod 40 is also provided with a charging handle 52 to manually charge the weapon and an ejection opening 54 through which spent cases are ejected. In order to expose the components of the firing mechanism for cleaning, maintenance or other purposes, the lower receiver 14b is mounted upon a pivot pin 56 and take down pin 58.

Before a detailed discussion of the firing mechanism incorporated in the lower receiver 14b, it would be profitable to briefly examine the structure of the bolt assembly 33. The bolt assembly 33, which is mounted for longitudinal reciprocating movement between retracted and battery positions within the upper receiver 14a, is of a type known in the prior art. The bolt carrier 50 of the bolt assembly 33 moves longitudinally with the receiver under the impetus of the operating rod 40. The guide lugs 60 and 62, defined on the upper part of the bolt carrier 50, function to prevent rotation of the bolt carrier 50 during longitudinal movements. Mounted for axial sliding movement and rotation within the bolt carrier 50 is a bolt 64 having a plurality of locking lugs 66 fashioned upon the front end thereof, the locking lugs 66 being adapted to pass through and lockingly engage a corresponding set of lugs 68 defined in the upper receiver 14a adjacent chamber 32. When the bolt 64 moves toward the chamber 32 to its battery position, the locking lugs 66 pass through the voids between the corresponding lugs 68 and then rotate to positions in which they lockingly engage the lugs 68 in accordance with the rotation of the bolt 64. The locking cooperation between the

lugs

66 and 68 holds the bolt 64 in the illustrated battery position to lock the bolt 64 against rearward movement, as is urged when a chambered cartridge is fired.

The bolt assembly 33 also includes a firing pin 70, slideably mounted within the bolt 64 and the bolt carrier 50 for restricted reciprocating axial movement. As best seen in FIGS. 2, and 6, a cam pin 72 extends through a bore in the bolt 64 and embodies an aperture which slidingly receives the firing pin 70. The cam pin 72 travels within a helical cam slot 74 in the bolt carrier 50 which is disposed between the

guide lugs

62 and 60. When relative longitudinal movement is occasioned between the bolt carrier 50 and the bolt 64, the cam pin 72 produces relative rotation between the bolt 64 and the bolt carrier 50, the

guide lugs

60 and 62 restraining the bolt carrier 50 against rotation. The firing pin 70 is restricted in its longitudinal movement with respect to the bolt carrier 50 and the bolt 64 by virtue of a pin 76 fixably secured to the bolt carrier 50 and extending within an aperture 78 in the rear of the firing pin 70. This restricted movement of the firing pin 70 with respect to the bolt carrier 50 and the bolt 64 prevents a chambered cartridge from being fired before the bolt 64 is locked. Hence, if for any reason the firing pin 70 should be struck when the bolt 64 is not locked, the chambered cartridge will not be fired.

For the purposes of illustrating the operation of the bolt assembly 33, assume that a cartridge has been fired and that the bolt assembly 33 is traveling in a rearward direction toward the buffer 79 its retracted position. Since the bolt 64 is locked by the engagement between the

cooperating lugs

66 and 68, rearward movement of the bolt carrier 50 will produce rotation of the cam pin 72 and hencerotation of the bolt 64. This rotation of the bolt 64 causes the locking lugs 66 to confront and register with the voids defined between the cooperating lugs 68 to allow rearward movement of the bolt 64 upon further movement of the bolt carrier 50. The driving force is transmitted to the bolt 64 via the cam pin 72 by the front surface of cam slot 74. During rearward movement or recoil of the bolt assembly 33, the expended cartridge is extracted and ejected. The dissipation of the rearward momentum of the bolt assembly 33 and operating rod 40 is primarily attributable to the operating spring 44 which is adapted, at the termination of recoil upon contact with the buffer 79, to urge the operating rod 40, and hence the bolt assembly 33, toward the battery position thereof. During forward movement of the bolt assembly 33, a new cartridge is stripped from the magazine 16 by bolt 64 and chambered.

The heart of the invention resides in a rate reducer which is incorporated in the firing mechanism mounted in the lower receiver 14b. In order to appreciate the construction of the firing mechanism, it is useful to refer to FIG. 2 in conjunction with FIGS. 3 and 4. Before continuing the discussion of the firing mechanism, it is important to note that the selector 80 is set for automatic fire and that the mechanism is cocked and ready to fire.

A hammer 82 is mounted on a pivot pin 83 for swinging movement between a recoil position and a fired position, the illustrated cocked position (FIGS. 2 and 3) being intermediate these extreme positions. A torsion spring 84 is coiled around the hub 86 of the hammer 82 to bias the hammer 82 toward the fired position. The hammer 82 includes a searing surface 88, which is engageable by the sear 90, and a notch 92, engagable by a leg 94 of a disconnect 96 during semiautomatic operation. The upper portion of the hammer 82 comprises a recess 98 in which a link 1100 is mounted for pivoting movement about a pivot pin 102. The link 100 is urged in a counterclockwise direction about pivot pin 162 by a spring and plunger assembly 104 such that the protrusion 106 of the link 100 projects from the outer contour of the hammer 82, the function of the protrusion 106 being explained hereinafter. Turning back to the sear 90 and the disconnect 96, it can be observed that both the sear 9t) and the disconnect 96 are mounted about a common pivot pin 108 an are biased in respective clockwise and counterclockwise directions by a compression spring 1 10 positioned therebetween.

The selector 80 is mounted upon a pin 118, fixedly secured in the lower receiver, to limit the movement of the sear 90 and disconnect 96 such that the firearm 12 may be rendered safe or adapted for semiautomatic or fully automatic operation, in accordance with the position of the selector 80. Briefly stated, when the selector 80 is moved to safe, the sear 90 is contacted such that movement of the trigger 22 cannot displace it out of engagement with hammer searing surface 88. In the semiautomatic position of the selector 80, the selector 80 is positioned such that the disconnect 96 may rotate under the influence of the compression spring 1 10 so as to position the leg 94 thereof under the notch 92 of hammer 82, thereby preventing clockwise rotation of the hammer 82. In the automatic position of the selector, which is that illustrated in FIGS. 2 and 3, the disconnect 96 is displaced clockwise about the pin 108 such that the leg 94 will not engage the notch 92 when the hammer moves towards the fired position from the recoil position.

As shown in FIG. 6, during recoil, the bolt assembly 33 drives the hammer 82 downwardly or counterclockwise about pivot pin 83. When the hammer 82 reaches its lower or counterclockwise limit of travel (referred to herein as the recoil position), the end of hammer 82 impacts upon a resilient buffer 122 which serves to cushion the loads imparted to the hammer 82 by the sudden stoppage of movement, this position being below or counterclockwise of the cocked position indicated in Flg. 3.

As best shown in FIGS. 2 and 5-10, a trigger rod 124 interconnects the sear 90 and the trigger 22. The sear 90, itself, comprises an upstanding arm portion 126 which is adapted to be pushed by the trigger rod 124 so as to rotate the sear 96 to thereby releasethe hammer 82 for falling movement. Thus, by virtue of the interconnection (not shown) between the trigger rod 124 and the trigger 22, rearward displacement of the trigger 22 causes rotation of the sear 90 such that the hammer 82 is disengaged therefrom.

A rate reducer mechanism is constituted by an inertia mass 134 and an automatic sear 136 in the form of a bar. The inertia mass 134 is mounted for pivoting movement between seated and displaced positions about a pin 137 and is biased to the seated position, as illustrated in FIG. 3, wherein the rear surface of the inertia mass abuts a buffer 138. This biasing is accomplished by a torsion spring 140, coiled about the hub of the inertia mass 134 and in contact with a fixed pin 142 located on the right side of the receiver, as is best shown in FIG. 4. The upper part of the inertia mass 134 adjacent the pivot pin 137 comprises contact surface 146 and a searing surface 148. The contact surface 146 is adapted to engage the protrusion 106 of link 100 upon falling of the hammer 82 from its recoil position so that the spring bias acting on the hammer 82 must overcome the inertia of the inertia mass 134 and the bias imposed thereupon by spring 140 in order to displace the inertia mass 134. Hence, since the hammer 82 must overcome the inertia of the inertia mass 134 and the bias of the torsion spring 140 to an extent sufficient to cause the protrusion 106 of link 100 to clear the contact surface 146, the time for the hammer 82 to fall from its recoil position to the fired position will be extended from that of a free falling hammer.

Obviously, it is necessary to provide an automatic sear device to delay hammer fall until the bolt 64 is locked. This function is achieved, in accordance with the invention, by the automatic sear 136 acting in concert with the inertia mass 134. The searing surface 148, fashioned on the hub of the inertia mass 134, is engaged by the surface 136a of automatic sear 136 to prevent the hammer 82 from rotatably displacing the inertia mass 134 until the bolt 64 is locked and the bolt carrier 50 is substantially in its battery position. To this end, the automatic sear 136 is biased toward the rear of the firearm 12 by a compression spring 136b disposed in the upper receiver 14a adjacent the chamber 32, as best shown in FiG. 5. When the bolt carrier 50 is initially, rearwardly displaced from its battery position, spring 136k acts to move the axially movable automatic sear 136 within its channel to the rear until a projection 136:: contacts an abutment pin 150, fixedly mounted in the upper receiver 14a. When this contact is established, the surface 136a of the automatic sear 136 will overlie the searing surface 148 of the inertia mass 134 such that the urging of the hammer 82 upon the surface 146 will not effect rotation of the inertia mass 134 so that the hammer 82 will be thereby prevented from moving to strike the firing pin 70. However, as the bolt carrier 50 assumes its battery position, an abutment 152, fashioned on the bolt carrier 50, contacts another projection 154 on the forward portion of the automatic sear 136 to axially move the automatic sear 136 toward the chamber 32, thereby to remove the surface 1360 from restraining contact with searing surface 148 of inertia mass 134. When the surface 136a of automatic sear 136 slides out of contact with the searing surface 148 of the inertia mass 134, the hammer 32 is then capable of rotating the inertia mass 134 in its falling movement toward the fired position.

OPERATION A. Automatic Operation With the firing mechanism in the cooked or seared configuration of FIG. 3 and the selector set for automatic fire, it should be apparent that depression of the trigger 22 will cause disengagement of the sear W) from the hammer searing surface 88, thereby allowing the hammer 82 to pivot under the bias of torsion spring 84 and eventually strike the firing pin 70 (FIG. 5). The striking of the firing pin 70 by the hammer 82 causes the bullet of the chambered cartridge to pass outward through the barrel 18 under the propelling force of the expanding gases. As previously described, a portion of these gases enters gas port 36 and drives operating rod 40 rearwardly. The rearward motion of the operating rod 40 is imparted to the bolt carrier 50 in a manner heretofore described.

The initial rearward movement of the operating rod 40 is depicted in FIG. 6, wherein the bolt carrier 50 has not yet moved to such an extent to cause the locking lugs 66 on the bolt 64 thereon to be completely rotated out of locking engagement with the corresponding lugs 68 on the receiver. As FIG. 6 shows, the motion imparted to the bolt carrier 50 by the operating rod 40 causes the end of the firing pin 70 to drive the hammer rearwardly or counterclockwise. It will be noted that in FIG. 6, the bolt carrier 51) has traveled a sufficient distance to the rear to remove the firing pin 70 from contact with the spent cartridge and to allow the automatic sear 136 to slide over the searing surface 148 of the inertia mass 134. In FIG. 6, the cam pin 72 is starting to rotate, thereby commencing rotation of the bolt 64 along with the integral locking lugs 66.

Further movement of the bolt carrier 50 from the position shown in FIG. 6 will cause sufficient rotation of the bolt 64 to enable the locking lugs 66 to register with the voids between the corresponding lugs 68 on the upper receiver 14a so that the end wall of the cam slot 74 will contact the cam pin 72 and thereby produce rearward travel of the bolt 64 to the position of FIG. 7. Movement of the bolt 64 from the position of FIG. 6 to that of FIG. 7 also extracts the spent cartridge.

FIG. 7 shows that the bolt carrier 50 has moved the hammer 82 to a position in which the link has been pivoted and depressed by the contact of protrusion 106 with the hub of the inertia mass 134. As can be observed from FIG. 7, the slight rotation of the link 100 about its pin 102 has slightly compressed the spring biased plunger 104. i

In FIG. 8, the bolt carrier 50 has produced a rearward rotation of the hammer 82 to its recoil position. Since the protrusion 106 on the link 100 has cleared the hub of the inertia mass 134, the link 1110 occupies its normal position. Also, in FIG. 8, the endof the hammer 32 is shown impinging upon the buffer 122. The case is ejected when the bolt 64 is intermediate the FIGS. 7 and 8 positions. After the bolt carrier 50 reaches its retracted position in which the buffer 79 is contacted, the force of operating spring 44 acting on the operating rod 40 will urge the bolt carrier 50 from the retracted position to the battery position.

The configuration shown in FIG. 9 depicts the cooperation between the hammer 82 and the inertia mass 134 when the bolt carrier 50 is moved forward of its retracted position, stripping a fresh cartridge from the magazine 16. As shown in FIG. 9, the protrusion 106 of link 1011 is in engagement with the contact surface 14-6 of inertia mass 134, thereby curtailing the fall of the hammer 82 to the fired position. This interruption in the hammer fall is, of course, due to the movement preventing engagement between the searing surface 148 of the inertia mass 134 and surface 136a of the automatic sear 136.

In FIG. 10, the fresh cartridge has been chambered by bolt 64 and the bolt carrier 50 is about to commence rotation of the cam pin 72 to lock the bolt 64 in the battery position. It will be noted from FIG. 10 that the firing pin 70 is maintained at a safe distance from the cartridge and that the automatic sear 136 continues to prevent displacement of the inertia mass 134 by hammer 82 and hence, the hammer 82 cannot yet complete its fall to the fired position.

As the bolt assembly 33 moves from the FIG. 11 to the FIG. 11 position (battery position), the bolt 64 is rotated and locked and, subsequently the abutment 152 in the bolt carrier 50 engages the projection 154 on the automatic sear 136 to axially move the automatic sear 136 forward against the bias of spring 136b. It should be noted that it is the last portion of the forward movement of the bolt carrier 50 which results in the surface 136a clearing the searing surface 148 of the inertia mass 134 to thereby permit the inertia mass 134 to be rotated by the protrusion 106 of link 1041. Also, this movement permits the firing pin 70 to assume a position wherein it can contact a cartridge. The hammer 82 will continue to rotate the inertia mass 134 until protrusion 106 clears the contact surface 146, at which time the hammer 82 will continue its forward movement to the fired position and the inertia mass 134 will return to its original or seated position (i.e., the position illustrated in FIGS. 4 through 8), this repositioning being occasioned by the bias of the torsion spring 1410 acting on the inertia mass 134.

Hence, the fall of the hammer 82 to the fired position during automatic operation is effectively delayed by the inertia of the inertia mass 134. After clearing the inertia mass 134, the hammer 82 falls to the fired position, illustrated in FIG. 5, to fire another cartridge which initiates another cycle. It will be appreciated that the time consumed by displacement of the inertia mass 134 provides the desired reduction in the inherent rate of fire. To discontinue automatic firing, it is merely necessary to release the trigger 22 so that the sear 90 will engage the hammer 82 during falling movement thereof.

B. semiautomatic Operation In general, with respect to semiautomatic operation, the inertia mass 134 is displaced as in automatic operation except that the falling of the hammer 82 is interrupted by the contact between the disconnect 96 and the hammer 82. More particularly, if a cartridge has been fired and the selector 80 occupies its semiautomatic position, the hammer 82 will rotate the inertia mass 134, as previously illustrated and described, and after clearing the inertia mass 134, the notch 92 will contact the leg 94 of the disconnect 96 to stop the falling movement of the hammer 82. This assumes, of course, that the operator of the firearm holds the trigger 22 in the depressed position. Upon releasing the trigger 22, both the disconnect 96 and the sear 90 will be caused to rotate clockwise about the pivot pin 10% so that the leg 94% moves out of locking engagement with the hammer 82 and the hammer 82 subsequently rotates a few degrees and engages the sear 90. It will be appreciated that this is the case with many automatic firearms. The hammer 82 is now in cocked position and may be again fired by depressing the trigger 22. It will be noted that the movement of the hammer 82 from the cocked to the fired position in semiautomatic operation is in no way affected by the inertia mass 134.

Obviously, variations, modifications and adaptations of the heretofore described structure are possible without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a firearm adapted for semiautomatic and automatic operation, the combination comprising:

a hammer mounted in the firearm for falling movement between recoil and fired positions;

a sear mounted in the firearm to engage the hammer and retain it in a cocked position intermediate the recoil and fired positions; and

an inertia mass movably mounted in the firearm such that falling movement of the hammer from the recoil position to the cocked position causes the hammer to engage and displace the inertia mass and to clear the inertia mass before reaching the cocked position in both semiautomatic and automatic operation and such that the hammer remains clear of the inertia mass in falling movement from the cocked position to the fired position in both semiautomatic and automatic operation.

2. The combination of claim 1, further including:

a bolt assembly mounted for reciprocating movement between retracted and battery positions in the firearm, the bolt assembly being contacted by the hammer in the fired position thereof; and

an automatic sear mounted in the firearm to engage the inertia mass such that displacement of the mass by the hammer is prevented, the automatic sear adapted to be contacted by the bolt assembly as it moves into the battery position to remove the automatic sear from engagement with the inertia mass and thereby permit displacement of the mass by the hammer.

3. The combination of claim 2, further including:

means to bias the inertia mass to a seated position in which it is initially engaged by the hammer; and

means to bias the automatic sear into engagement with the mass when the bolt assembly is displaced from the battery position.

4. In an automatic firearm:

a hammer mounted in the firearm for movement between recoil, cocked and fired positions, the cocked position being intermediate the recoil and fired positions;

a movably mounted inertia mass adapted to be engaged, displaced, and cleared by the hammer during movement between the recoil and cocked positions;

an automatic sear bar mounted in the firearm for axial movement between a first position in engagement with the mass and a second position in which the hammer may displace the mass, the first position being to the rear of the second position; and

spring means to urge the sear bar rearwardly to the first position.

5. The combination of claim 4, further including:

a bolt assembly mounted in the firearm for movement between retracted and battery positions, the bolt assembly being contacted by the hammer in the fired position thereof; and

means on the bolt assembly to contact the automatic sear bar intermediate the retracted and battery positions and to move the automatic sear bar from the first position to the second position during the latter portion of bolt assembly movement from the retracted position to the battery position.

6. The combination of claim 5, further including:

means to bias the inertia mass to a seated position in which it is initially engaged by the hammer.

7. In a firearm adapted for automatic and semiautomatic operation, the combination comprising:

a receiver section;

a bolt assembly mounted in the receiver section for reciprocating movement between retracted and battery positions;

a hammer mounted in the receiver section for pivoting movement between recoil and fired positions, the hammer contacting the bolt assembly in the fired position;

a sear mounted in the receiver section to engage and retain the hammer in a cocked position inter mediate the recoil and fired positions;

an inertia mass mounted in the receiver section for pivoting movement between a seated and displaced position such that falling movement of the hammer from the recoil position to the cocked position causes the hammer to engage and displace the inertia mass and to clear the inertia mass before reaching the cocked position and such that the hammer remains clear of the inertia mass in falling movement from the cooked position to the fired position in both semiautomatic and automatic operation;

means to return the inertia mass to the seated position after the inertia mass is cleared by the hammer during its falling movement;

an automatic sear mounted for movement in the receiver section between a first position in which it engages the inertia mass in the seated position thereof and a second position in which the hammer may displace the inertia mass; and

means to move the automatic sear from the first position to the second position as the bolt assembly moves into the battery position.

8. The combination of claim 7, wherein the inertia mass comprises:

a hub having a searing surface thereupon; and

wherein the automatic sear comprises:

a bar axially movable between the first and second positions and having a surface which overlies and engages the searing surface of the hub when the bar is in the first position and slides out of contact with the searing surface of the hub as the bar assumes the second position; and

means to move the bar from the second position to the first position during movement of the bolt assembly from the battery position to the retracted position.

9. The combination of claim 7, further including;

a selector in the receiver section for selecting either automatic or semiautomatic operation; and a disconnect 1n the receiver section to engage the hammer and prevent its fall toward the fired position when the selector is positioned for semiautomatic operation and the hammer engaging sear is out of engaging contact with the hammer.

Claims

1. In a firearm adapted for semiautomatic and automatic operation, the combination comprising: a hammer mounted in the firearm for falling movement between recoil and fired positions; a sear mounted in the firearm to engage the hammer and retain it in a cocked position intermediate the recoil and fired positions; and an inertia mass movably mounted in the firearm such that falling movement of the hammer from the recoil position to the cocked position causes the hammer to engage and displace the inertia mass and to clear the inertia mass before reaching the cocked position in both semiautomatic and automatic operation and such that the hammer remains clear of the inertia mass in falling movement from the cocked position to the fired position in both semiautomatic and automatic operation.

2. The combination of claim 1, further including: a bolt assembly mounted for reciprocating movement between retracted and battery positions in the firearm, the bolt assembly being contacted by the hammer in the fired position thereof; and an automatic sear mounted in the firearm to engage the inertia mass such that displacement of the mass by the hammer is prevented, the automatic sear adapted to be contacted by the bolt assembly as it moves into the battery position to remove the automatic sear from engagement with the inertia mass and thereby permit displacement of the mass by the hammer.

3. The combination of claim 2, further including: means to bias the inertia mass to a seated position in which it is initially engaged by the hammer; and means to bias the automatic sear into engagement with the mass when the bolt assembly is displaced from the battery position.

4. In an automatic firearm: a hammer mounted in the firearm for movement between recoil, cocked and fired positions, the cocked position being intermediate the recoil and fired positions; a movably mounted inertia mass adapted to be engaged, displaced, and cleared by the hammer during movement between the recoil and cocked positions; an automatic sear bar mounted in the firearm for axial movement between a first position in engagement with the mass and a second position in which the hammer may displace the mass, the first position being to the rear of the second position; and spring means to urge the sear bar rearwardly to the first position.

5. The combination of claim 4, further including: a bolt assembly mounted in the firearm for movement between retracted and battery positions, the bolt assembly being contacted by the hammer in the fired position thereof; and means on the bolt assembly to contact the automAtic sear bar intermediate the retracted and battery positions and to move the automatic sear bar from the first position to the second position during the latter portion of bolt assembly movement from the retracted position to the battery position.

6. The combination of claim 5, further including: means to bias the inertia mass to a seated position in which it is initially engaged by the hammer.

7. In a firearm adapted for automatic and semiautomatic operation, the combination comprising: a receiver section; a bolt assembly mounted in the receiver section for reciprocating movement between retracted and battery positions; a hammer mounted in the receiver section for pivoting movement between recoil and fired positions, the hammer contacting the bolt assembly in the fired position; a sear mounted in the receiver section to engage and retain the hammer in a cocked position intermediate the recoil and fired positions; an inertia mass mounted in the receiver section for pivoting movement between a seated and displaced position such that falling movement of the hammer from the recoil position to the cocked position causes the hammer to engage and displace the inertia mass and to clear the inertia mass before reaching the cocked position and such that the hammer remains clear of the inertia mass in falling movement from the cocked position to the fired position in both semiautomatic and automatic operation; means to return the inertia mass to the seated position after the inertia mass is cleared by the hammer during its falling movement; an automatic sear mounted for movement in the receiver section between a first position in which it engages the inertia mass in the seated position thereof and a second position in which the hammer may displace the inertia mass; and means to move the automatic sear from the first position to the second position as the bolt assembly moves into the battery position.

8. The combination of claim 7, wherein the inertia mass comprises: a hub having a searing surface thereupon; and wherein the automatic sear comprises: a bar axially movable between the first and second positions and having a surface which overlies and engages the searing surface of the hub when the bar is in the first position and slides out of contact with the searing surface of the hub as the bar assumes the second position; and means to move the bar from the second position to the first position during movement of the bolt assembly from the battery position to the retracted position.

9. The combination of claim 7, further including; a selector in the receiver section for selecting either automatic or semiautomatic operation; and a disconnect in the receiver section to engage the hammer and prevent its fall toward the fired position when the selector is positioned for semiautomatic operation and the hammer engaging sear is out of engaging contact with the hammer.