Collapsible stock assembly

A collapsible stock assembly for a firearm includes a stock body defining a buffer tube passage for slidably accommodating a firearm buffer tube therein. An adjustment slit communicates with the buffer tube passage along a forward portion thereof. A first adjustment mechanism canied by the stock body includes a buffer tube engagement element that can extend into the buffer tube passage and is selectively positionable by a first operating lever. A second operating mechanism includes a second operating lever that is operable to selectively compress the adjustment slit. Disengaging the first adjustment mechanism automatically disengages the second adjustment mechanism. Excessive force on the stock in several embodiments automatically disengages both adjustment mechanisms and minimizes damage to stock assembly and/or buffer tube.

FIELD OF THE INVENTION

The present invention relates to collapsible stock assemblies for firearms, and more particularly, to collapsible rifle stock assemblies.

BACKGROUND OF THE INVENTION

Various firearms, and particularly assault rifles, have been designed to include a collapsible stock. In general, such firearms include a buffer tube on which the collapsible stock is axially slidable. Some mechanism is typically included on the stock to fix its axial position on the buffer tube to allow the user to quickly adjust the effective length of the stock.

One example of such a firearm is the M-4 rifle. The M-4 is a widely used and popular rifle, and users value the ability to rapidly adjust the effective length of the stock. However, problems experienced with the collapsible stock of the M-4 rifle can be illustrative of shortcoming of current designs.

For example, while the axial position of the collapsible stock is maintained relatively securely, clearances between the stock and buffer tube often result in a loose, wobbly feel—particularly when the collapsible stock is in the fully extended position and a relatively small portion of the buffer tube is engaged within the collapsible stock. This loose, wobbly feel can be distracting to the user and adversely impact marksmanship.

This type of fit problem can be exacerbated when, as is the case with the M-4 rifle, models of a given rifle are available with varying buffer tube diameters. A collapsible stock dimensioned to accommodate larger buffer tube diameters will tend to be excessively wobbly on smaller buffer tube diameters. On the other hand, a collapsible stock dimensioned to more closely accommodate smaller buffer tubes may not fit on larger buffer tubes, at all.

Additionally, with repeated cycling of the collapsible stock assembly, wear of the stock assembly (typically plastic) against the buffer tube (typically metal) will increase clearances. Accordingly, the fit problems can become worse over time.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide an improved stock assembly. According to an embodiment of the present invention, a collapsible stock assembly for a firearm includes a stock body defining a buffer tube passage for slidably accommodating a buffer tube of the firearm therein. An adjustment slit communicates with the buffer tube passage along a forward portion thereof. A first adjustment mechanism carried by the stock body includes a buffer tube engagement element that can extend into the buffer tube passage and is selectively positionable by a first operating lever. A second operating mechanism includes a second operating lever that is operable to selectively compress the adjustment slit.

According to an aspect of the present invention, disengaging the first adjustment mechanism can operate to automatically disengage the second adjustment mechanism.

These and other objects, aspects and advantages of the present invention will be better appreciated in view of the drawings and following detailed description of preferred embodiments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to an embodiment of the present invention, with reference toFIGS. 1 and 2, a collapsible stock10for a firearm includes a stock body20, a first adjustment mechanism22and a second adjustment mechanism24. The first and second adjustment mechanisms22,24cooperate to releasably secure the stock body20at a plurality of discrete locations to and along a buffer tube26of the firearm.

The stock body20defines a buffer tube passage30therein, a forward end of the passage30terminating at a buffer tube insertion opening32. The buffer tube insertion opening32permits a rear end of buffer tube26to be inserted therethrough into the passage30along an axis thereof. The buffer tube passage30is dimensioned to slidably accommodate at least a portion of the buffer tube26therein. The buffer tube passage30includes an axially-extending keyway34along a lower side thereof to accommodate a key36on the underside of the buffer tube26. The stock body20is preferably integrally molded from a strong and substantially rigid plastic material.

The stock body20additionally defines an adjustment slit40extending axially rearwards from the buffer tube insertion opening32. The adjustment slit40communicates with a forward portion of the buffer tube passage30and extends radially outward therefrom. Compression of the adjustment slit40by the second adjustment mechanism24allows the buffer tube passage30proximate the buffer tube insertion opening32to clamp securely around the buffer tube26. The capacity of the stock body20for flexion in this area is enhanced by a transverse slit42defined extending through the stock body rearward of the adjustment slit40and extending radially downward from the buffer tube passage30.

The stock body20advantageously includes a buffer tube accommodation portion44, in which the buffer tube passage30is defined, and an angled lower portion46extending rearwardly and downwardly from a forward end of the buffer tube accommodation portion44. A central opening48is defined between the portions44,46. A butt portion50extends generally vertically between rearward ends of the buffer tube accommodation portion44and angled lower portions46and such portions surrounds and defines the central opening48.

A sling loop52is formed on an upper surface of the buffer tube accommodation portion44, defining a passage for a sling or other carrying device for the firearm. A plurality of finger grooves54are defined along a lower surface of the angled lower portion46to facilitate grasping by a user. A removable butt plate56snaps onto a rear surface of the butt portion50and is further secured thereto by a pair of spaced fasteners60, such as screws. A bushing opening62is defined in an elbow between the angled lower portion46and the butt portion50, and removably accommodates a bushing64through which a sling clip or other accessory can be pivotably routed.

Other features are defined in the stock body20that will be described in connection with associated components of the first and second adjustment mechanisms22,24.

Referring toFIGS. 1-15, the first adjustment mechanism22includes a buffer tube engagement element70, a first operating lever72, and a biasing mechanism74, such as a compression spring. The biasing mechanism74urges the buffer tube engagement element70at least partially into the buffer tube passage30and into engagement with the buffer tube26, and the first operating lever72is operable to move the engagement element70downwards and out of engagement with the buffer tube26. By selectively engaging detents76in the key36of the buffer tube26, the first operating mechanism22is operable to releasably secure the collapsible stock assembly10at a plurality of discrete points along the buffer tube26.

Referring more particularly toFIGS. 1,2and14, the buffer tube engagement element70and biasing mechanism74are accommodated in an engagement element channel80defined in the stock body20intersecting the buffer tube passage30. Also defined in the stock body20below the buffer tube passage30are an operator slot82and a retention pin hole84.

The buffer tube engagement element70is retained within the engagement element channel80by an operator pin86inserted through the operator slot82and an operator bore90in the engagement element70. The biasing mechanism74is retained in the channel80below the buffer tube engagement element70by a retention pin92inserted through the retention pin hole84. The biasing mechanism74acts on the buffer tube engagement element70via a piston94inserted into a central bore96(seeFIG. 4) defined in the engagement element70. An upper end of the piston94engages a slot100in the center of the operator pin86, retaining the operator pin86in place.

Referring more particularly toFIGS. 3 and 4, the buffer tube engagement element70is generally cylindrical with a reduced-diameter upper portion102. On a side facing the buffer tube insertion opening32, the engagement element70preferably includes first and second engagement faces104,106. With the buffer tube engagement element70displaced fully upwards, the engagement faces104,106protrude into the buffer tube passage30. The first engagement face104is angled rearwardly away from the insertion opening32. The second engagement face106shares a common edge110with the first engagement face104, and from that edge110is angled rearwardly away from the insertion opening32at a steeper angle than the first engagement face104.

With the buffer tube engagement element70fully extended into one of the detents76of the buffer tube26, the first engagement face104is initially encountered in response to forces tending to drive the stock assembly10forward on the buffer tube26. The more vertical arrangement of the first face104provides greater resistance to such forward movement, and the angle should be set so as to prevent such movement in response to forces encountered during routine operation of a the firearm to which the buffer tube26is attached. For example, recoil forces should not be sufficient to overcome the engagement between any of the detents76with the first engagement face104.

However, greater forces, such as incurred when inadvertently dropping the firearm on the butt plate56from a height of several feet or using the rifle and butt stock as a battering ram, will be great enough to drive the buffer tube engagement element70downwards such that the second engagement face106is encountered by the corresponding detent76. The steeper angle of the second engagement face106results in a lower resistance to further downward movement of the buffer tube engagement element70, thus forward motion of the collapsible stock assembly10will continue at an accelerated pace, overcoming engagement with any additional detents76, until the external force is no longer applied or the stock assembly10reaches the physical limit of its most forward motion on the buffer tube. Thus, the collapsible stock assembly10can provide a self-releasing function and For act as a shock absorber to prevent damage to the buffer tube engagement element70if the firearm is dropped or otherwise has excessive forces applied to the butt stock or is mishandled. Also, damage to the buffer tube26, and particularly to the detents76, and stock assembly10is minimized with the use of element70.

Referring toFIGS. 5 and 6, in a second embodiment of the buffer tube engagement element70′, there are no angled engagement faces and the reduced diameter upper portion102′ is simply cylindrical and may permit damage to the butt stock and/or buffer tube26due to the fact that the aforementioned self-releasing is not provided by element70′.

Referring toFIGS. 7 and 8, a third embodiment of the buffer tube engagement element70A is shown having a rounded engagement face106A on a side facing the buffer tube insertion opening32extending only on the reduced-diameter upper portion102A. Use of element70A, rather than element70, would result in a similar release of the stock assembly10from any of the detents76rearwardly of the most forward detent76of buffer tube26so that element70A would engage in such most forward detent76, which may cause some damage to the stock assembly10and/or buffer tube26.

Referring toFIGS. 9 and 10, a fourth embodiment of the buffer tube engagement element70B is shown having a bulbous or bullet-shaped upper portion102B, where the engagement surface106B is located similarly toFIGS. 7 and 8, and extend only on the reduced diameter upper portion102B. Use of element70B has an advantage of being less costly to manufacture than element70or even element70A, while providing similar results to that set forth above with reference toFIGS. 7 and 8.

Referring toFIGS. 11 and 12, the first operating lever72extends between first and second ends112,114, being pivotably mounted therebetween to the stock body20. Mounting holes116are defined in opposite sides of the first operating lever72that snap over mounting protrusions120(seeFIG. 1) on opposite sides of the stock body20. The first end112extends into the central opening48defined by the buffer tube accommodation, angled lower and butt portions44,46,50of the stock body20and is operable by a user extending his fingers therethrough and urging the first end112upwards. To facilitate operation, the first end112can be textured. The second end114is forked to extend on opposite sides of the stock body20, facilitating ambidextrous operation of the collapsible stock assembly10, as will be explained in greater detail below.

InFIGS. 13-15the first adjustment mechanism22is in the engaged position, with the buffer tube engagement element70fully engaged within a detent76of the buffer tube26. Except as described above in connection with the dropped firearm scenario, the collapsible stock assembly10is inhibited from forward and rearward motion by this engagement.

Referring toFIGS. 16-18, to allow forward or rearward motion, in the direction of arrow122, the first operating lever72first end112is pivoted toward the stock body20in the direction of arrow124. Consequently, the first operating lever72second end114moves downwardly in the direction of arrow126. The second end114engages the ends of the operator pin86, urging the buffer tube engagement element70downwardly against the biasing mechanism74. Once the engagement element70is completely clear of the detent76, the stock body20can be moved forwardly or rearwardly in the direction of arrow122. To allow the engagement element70to engage another detent, the first operating lever72first end112is released and the biasing mechanism74urges the engagement element70upwardly.

Referring to FIGS.2and19-21, the second adjustment mechanism24includes a second operating lever130having a stock body engagement portion132that variably engages an underlying engagement surface134on the stock body20. The second operating lever130is pivotably mounted to the stock body20by one or fasteners136, for instance a machine screw and lock nut, inserted through a second operating lever mounting bore140defined in the stock body20. Advantageously, engagement surfaces134are formed on both sides of the stock body20to allow the second operating lever130to be mounted on either side thereof. The unused engagement surface can be covered by a blank142.

The second operating lever130has a first end144and a second end146. The first end144carries the stock body engagement portion132and defines a central mounting bore150for receiving the fasteners136. Advantageously, a portion of the mounting bore150can be hexagonal to closely accommodate a nut therein. The second end146extends rearwardly from the first end144and can be contoured and textured for easy manipulation by a user.

The stock body engagement portion132carries a plurality of engagement teeth152that extend from the second operating lever130first end144toward the stock body20. The engagement surface134includes a plurality of adjacent high and low zones154,156underlying the engagement teeth152. With the second operating lever130pivoted via manipulation of the second end146such that the teeth152overlie high zones156, the adjustment slit40of the stock body20is compressed (as inFIG. 15). Consequently, the end of the buffer tube passage30proximate the buffer tube insertion opening32tightly engages the buffer tube26, inhibiting slop or play between the collapsible stock assembly10and the buffer tube26during use of the associated firearm.

To release the second adjustment mechanism24, the second end146is urged downwardly, in the direction of arrow160(as inFIG. 18). This pivots the engagement teeth152over the low zones156, allowing the adjustment slit40to open and disengage the end of the buffer tube passage30proximate the buffer tube insertion opening32from the buffer tube26. Advantageously, the second adjustment mechanism24is automatically disengaged when the first adjustment mechanism22is disengaged, since one of the bifurcated second ends114proximate lever130moves downwardly and causes mechanism24to disengage.

As seen inFIGS. 15 and 18, the first operating lever72second end114is in close proximity to the second operating lever130second end146, so that manual pivoting the first operating lever72to disengage the buffer tube engagement element70will result in pivoting of the second operating lever130to open the adjustment slit40. In the depicted embodiment, the first operating lever72second end114acts on the second operating lever130second end146via the operator pin86.

Because the operator pin86and the first operating lever72second end114extend on both sides of the stock body20, automatic disengagement of the second adjustment mechanism24will occur regardless of the side on which the second operating lever130is mounted. The second operating lever130second end146can also include operator pin grooves162(seeFIG. 20) to facilitate engagement of the operator pin86when mounted on either side.

From the foregoing, it will be appreciated that a collapsible stock assembly according to the present invention allows quick re-positioning of the stock body according to the needs or preferences of a user without sacrificing the solid feel. Additionally, the addition of the second adjustment mechanism24is accomplished without requiring any additional user actions to disengage. Moreover, the useful life of the collapsible stock assembly is increased, as increased play resulting from wear in adjustment mechanisms can be avoided by simply tightening the fasteners136to adjust the tension exerted by the second adjustment mechanism24. Also, if wear does occur, the second adjustment mechanism24may be able to compensate for such wear thereby extending the useable life of the butt stock and/or the rifle buffer tube26.

For some firearm models, buffer tubes are available in multiple sizes. For example, for AR/M4 stocks the buffer tubes come in a Mil-Spec size and a slightly larger Commercial size. For many collapsible stocks, this means either a different stock must be used for different buffer tube sizes, or additional looseness is experienced when using the stock on a Mil-Spec buffer tube.

The collapsible stock assembly10can advantageously include sizing components to ensure a close fit for multiple sizes. Referring toFIG. 2, the sizing components include a sizing shim170and a sizing pin172. The sizing shim170is releasable secured in the adjustment slit40and the sizing pin172is releasably secured in a sizing passage174defined in the stock body20generally perpendicular to and partially intersecting the buffer tube passage30.

Referring toFIGS. 2 and 22, the sizing shim170includes a shim surface176with a retention portion180depending downwardly therefrom. The shim surface176rests in the keyway34and elevates the key36of the buffer tube26when the shim170is installed. The retention portion180extends into the adjustment slit40and has retention bore182defined therein so that the shim170is releasable secured in place by the fastener136of the second adjustment mechanism24.

Referring toFIGS. 23 and 24, the sizing pin172extends along a sizing pin axis184and has first and second sizing faces190,192. The second sizing face192is farther from the sizing pin axis184than the first sizing face190. When the sizing pin172is inserted into the sizing passage174with the second sizing face192oriented upwardly, the second sizing face192protrudes into the keyway34(seeFIG. 14) and cooperates with the sizing shim170to elevate the key36of the buffer tube26. Correct orientation of the sizing pin172is ensured by complementary protrusions196and recesses200on the pin172and sizing passage174. Inadvertent removal of the sizing pin172is prevented by interference from the first operating lever72second end114.

If the collapsible stock assembly10is to be used with a large buffer tube, the sizing shim170is removed and the sizing pin172is removed and reinstalled with the first sizing face190oriented upwardly. The key of the larger buffer tube can extend all the way to the bottom of the keyway34. As will be appreciated, the sizing components thereby allow the collapsible stock assembly10to accommodate buffer tubes of multiple sizes without sacrificing a firm, reliable fit.

In general, the foregoing description is provided for exemplary and illustrative purposes; the present invention is not necessarily limited thereto. Rather, those skilled in the art will appreciate that additional modifications, as well as adaptations for particular circumstances, will fall within the scope of the invention as herein shown and described and the claims appended hereto.