Abstract:
Apparatus and methods are disclosed for releasably securing a retractable shoulder stock relative to the casing of a firearm. The retractable shoulder stock includes a slide rail which is displaceable relative to the casing. The slide rail defines a recess. The shoulder stock also includes a catch lever which is mounted for rotation about an axis. The catch lever has a peripheral surface that can be manually engaged to rotate the catch lever about the axis. The catch lever is positioned to selectively engage in the recess to releasably lock the slide rail in a first predetermined position.

Description:
RELATED APPLICATION 
     This patent is a continuing application which claims priority under 35 U.S.C. §120 from International Application Serial No. PCT/EP00/06895, filed Jul. 19, 2000. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to firearms, and, more particularly, to a retractable shoulder stock for a firearm and a catch lever for such a shoulder stock. 
     BACKGROUND OF THE INVENTION 
     The terms used in this document to describe relative position, such as “forward,” “top,” “left” and so forth are referenced to a weapon which is properly positioned to deliver a horizontal shot, with the direction of shooting being toward the front (i.e., away from the shooter). The same convention also applies to the corresponding directional references (“toward the front,” “toward the top,” “to the left,” and so forth). 
     Automatic guns or machine guns often have an extendable shoulder stock which is mounted on guide rods and which can be secured by means of a catch mechanism. In U.S. Pat. No. 3,570,162, for example, the shoulder stock is mounted on a rod which is guided in a pipe so that it can be displaced longitudinally. A retaining claw passes through the pipe wall and engages in a corresponding catch notch of the rod so that the shoulder stock can be secured in the inserted and extracted positions. U.S. Pat. No. 4,383,384 also discloses an extendable shoulder stock. That shoulder stock is guided by two parallel rods, one of which can be locked by a catch pin which engages in corresponding recesses in the rod. 
     In addition, U.S. Pat. No. 3,137,958 describes an adjustable shoulder stock which is guided by two parallel extractable rods. The rods have catch notches. A catch body that is displaceable across the rods is engaged in the catch notches, thereby securing the position of the shoulder stock. U.S. Pat. No. 5,367,812 discloses another adjusting mechanism, where the rods mounted on the shoulder stock can be extended by means of screw-on elements. 
     Finally, German Utility Model 88 07 539 U1 discloses a shoulder stock with a receiving pipe in which a supporting rod or a supporting pipe can be telescoped and locked in position. The supporting rod or pipe is locked by locking screws which engage in the supporting rod or supporting pipe when in the desired position. 
     These known arrangements have the disadvantage that there is a certain play in the shoulder stock even in the locked state. This play has a negative effect on the stability of the gun, which stability is necessary to deliver a well-aimed shot. 
     A much better solution has been found to be the shoulder stock known from German Patent 1,225,517 by the owner of the present patent. The stock disclosed in that patent is mounted on slide rails which can be locked at the end of the gun casing by a locking element that is mounted so it can rotate. Locking projections of this element engage in corresponding recesses on the slide rail, preferably in such a way that they are put under tension in the radial direction to the axis of rotation of the locking element. Due to this tension, the shoulder stock has an increased stability in the locked state comparable to that of a one-piece rigid gun butt. 
     In a preferred implementation of the shoulder stock of German Patent 1,225,517, the locking element is designed as a ring-shaped base body and is mounted on a sleeve-shaped casing in the interior of the gun casing. The locking element is, thus, engaged with an operating ring which is used to operate the locking element. The operating ring is provided with an operating wing and is mounted outside the gun casing. This design is characterized by a great robustness and reliability and has proven successful in long-term use (e.g., in the case of the G3 gun of the Deutsche Bundeswehr [German military]). In particular, the shoulder stock is also capable of absorbing high forces, such as that required when firing shells or grenades, for example. 
     However, the design also includes disadvantages. For example, this design is relatively heavy and takes up a lot of space due to the massive cylinder-shaped construction. It, therefore, seems overdimensioned for certain applications (e.g., for light machine guns or other weapons that do not have such high stability requirements). 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the invention, a retractable shoulder stock is provided for use with a firearm having a casing . The retractable shoulder stock includes a slide rail which is displaceable relative to the casing of the firearm. The slide rail defines at least one recess. The shoulder stock also includes a catch lever which is mounted for rotation about an axis. The catch lever has a peripheral surface that can be manually engaged to rotate the catch lever about the axis. The catch lever is positioned to selectively engage in the at least one recess to releasably lock the slide rail in a first predetermined position. 
     In accordance with another aspect of the invention, a method of releasably securing a retractable stock of a firearm in a first predetermined position is provided. The method includes the steps of: pivoting a catch lever to disengage the catch lever from a first recess defined in a slide rail associated with the retractable stock; moving the slide rail; and pivoting the catch lever to engage a second recess defined in the slide rail. 
     Other features and advantages are inherent in the disclosed apparatus or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a an inclined, left side view of a first exemplary shoulder stock constructed in accordance with the teachings of the invention. 
     FIG. 2 is a front, sectional view taken along lines I—I of FIG.  1 . 
     FIG. 3 is a partial sectional view of a second exemplary shoulder stock constructed in accordance with the teachings of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a shoulder stock  1  of a machine gun. The stock  1  has two slide rails  3   a  and  3   b  having rear ends mounted on a shoulder cap  5 . The cap  5  connects the two slide rails  3   a ,  3   b  to one another. The two slide rails  3   a ,  3   b  pass through suitably designed openings  7   a  and  7   b  in an end plate  9  of the gun casing. The slide rails  3   a ,  3   b  are mounted so they can be displaced in the longitudinal direction of the gun through the openings  7   a ,  7   b  as well as through other guides (not shown) on the gun casing. A catch lever  11  is integrated into the end plate  9 . The catch lever  11  simultaneously engages in recesses  13   a ,  13   b  in the slide rails  3   a ,  3   b , so that the rails  13   a ,  13   b  are locked to prevent displacement. To visualize engagement of the catch lever  11  in the recess  13   b , the end plate  9  is shown in FIG. 1 with a cutout at  14 . The shoulder stock  1  is secured in this way in the use position shown here. In this position, the slide rails  3   a ,  3   b  project approx. 200 mm out of the end plate toward the rear. The front portions of the slide rails  3   a ,  3   b  which are then still mounted in the gun casing have a sufficient length (approx. 100 mm) to be securely supported in the gun casing. This imparts additional stability to the shoulder stock  1  in the use position. The slide rails  3   a ,  3   b  have additional recesses  23   a ,  23   b  on their rear ends, close to the shoulder cap  5 , serving to secure the shoulder stock in the retracted position (i.e., in the resting position), in a similar manner (i.e., by engagement with the lever  11 ). 
     Furthermore, a securing lever  15  is integrated into the end plate  9 . The securing lever  15  engages in a recess  25  on the slide rail  3   b ; its function is described in greater detail below. 
     FIG. 2 shows a cross sectional view taken along line I—I through the end plate  9 . The catch lever  11  is mounted without play on a pin  17  so it can rotate. The pin is mounted on the end plate  9 , with its central axis being the axis of rotation of the catch lever  11 . The pin  17  is located exactly between the two slide rails  3   a ,  3   b , so that the axis of rotation of the catch lever  11  is arranged concentrically with the slide rails  3   a ,  3   b . The catch lever  11  has flat areas  11   a  and  11   b  with which it rests on the top side of the slide rail  3   a  and on the bottom side of slide rail  3   b , respectively. The catch lever  11  is loaded by a spring  19 . The spring  19  is mounted with one end in a blind hole  11   c  located in the catch lever  11 . The spring  19  is supported at its other end against the end plate  9 . Due to the force of the spring  19 , a counterclockwise torque acts on the catch lever  11 , so that the slide rails  3   a ,  3   b  are in turn pressed down and up, respectively, by the catch lever  11 . The slide rails  3   a ,  3   b  are in this way put under tension toward one another and against their guides in the gun casing. The play in the slide rails  3   a ,  3   b  is, thus, reduced and the stability of the shoulder stock  1  is increased. 
     The recesses  13   a ,  13   b ,  23   a ,  23   b  are designed as grooves running across the longitudinal direction of the gun, passing through the respective slide rails  3   a ,  3   b  in their width. The slide rails  3   a ,  3   b  each have a substantially rectangular cross section which is curved slightly outward on the outer side. This shape enhances the torsional rigidity of the shoulder stock  1  and at the same time takes up little space in terms of width. The flat areas  11   a ,  11   b  of the catch lever  11  rest on the slide rails  3   a ,  3   b  over their entire width. The catch lever  11  is, thus, securely in contact with the slide rails  3   a ,  3   b  in their displacement. Therefore, no longitudinal grooves or the like for guiding the catch lever  11  are necessary on the slide rails  3   a ,  3   b . Thus, the slide rails can be manufactured more easily and less expensively. 
     In the diagram shown here, the shoulder stock  1  is secured in the use position. Specifically, the catch lever  11  engages in the recesses  13   a ,  13   b  on the slide rails  3   a ,  3   b . To release the lock, the catch lever  11  is turned clockwise against the force of the spring  19  to remove it from recesses  13   a ,  13   b . The slide rails  3   a ,  3   b  can then be pushed into the gun casing to insert the shoulder stock  1 . If the catch lever  11  is released during the insertion of the shoulder stock  1 , it rests on the on the top side of slide rail  3   a  and/or on the bottom side of slide rail  3   b  due to the force of the spring  19  until it automatically engages in the two recesses  23   a ,  23   b  with further insertion of the slide rails  3   a ,  3   b . The shoulder stock  1  is then secured in its resting position in which the shoulder cap  5  is at a slight distance from the end plate  9 . 
     To make it easier for the marksman to grip the catch lever  11 , the catch lever  11  is lengthened on the side of the slide rail  3   a , in such a way that its outer periphery projects out of the end plate  9  of the gun casing on this side to form a handle  11   d . The outer periphery, thus, extends beyond the outer ends of the recesses  13   a ,  13   b  (and the gun casing as well) at this point. The handle  11   d  has a trough-shaped recess and a grooved surface (see FIG.  2 ), so that the catch lever  11  can be gripped easily there and operated by the marksman&#39;s finger. 
     FIG. 2 shows that the handle  11   d  and the contact surfaces  11   a ,  11   b , are integrated into one part, namely the catch lever  11 . Consequently, no intermediate elements or the like are necessary. The design of the shoulder stock  1  is thus greatly simplified in comparison with the known solutions, thereby, saving on space and weight. Therefore, the shoulder stock of FIG. 1 has by a very compact and lightweight design which makes it especially suitable for machine guns and light machine guns. Thus, the shoulder stock  1  illustrated in FIGS. 1 and 2 is intended for use in a machine gun whose total weight is approx. 1.5 kg, but other types of guns and guns with different weights could also benefit from the use of this stock. 
     The securing lever  15  is mounted without play on the pin  17  so it can rotate in a manner like that used with the catch lever  11 . The securing lever  15  is placed under load in the clockwise direction of rotation (see FIG. 2) by a spring  29 . Due to the force of the spring  29 , the securing lever  15  rests on the top side of the slide rail  3   b  and engages in the recess  25  in the position illustrated here. Recess  25  passes like a groove through the slide rail  3   b  in the transverse direction, running upward on its rear side in the form of an inclined face as shown in FIG.  1 . Therefore, the securing lever  15  easily slides out of recess  25  without further manipulation when the slide rail  3   b  is inserted. This ensures that the securing lever  15  does not interfere with the insertion of the shoulder stock  1 . The function of the securing lever  15  is that the marksman cannot unintentionally pull the shoulder stock  1  completely out. This could otherwise happen if the marksman would hold the catch lever  11  upward under pressure while pulling the shoulder stock  1  out. Then the catch lever  11  cannot engage in the recesses  13   a ,  13   b , so, absent the securing lever  15 , the slide rails  3   a ,  3   b  could slide completely out of their guides in the gun casing. However, the securing lever  15  prevents the shoulder stock  1  from being extracted completely in that it automatically engages in the recess  25  under the load of the spring  29 . The slide rail  3   b  is then locked to prevent it from being displaced in the direction of extraction, and the shoulder stock  1  is secured to prevent further extraction. 
     For the case when the marksman would like to intentionally remove the shoulder stock, he can release the lock by means of the securing lever  15 . To do so, he must push the securing lever  15  upward, like the catch lever  11 , against the force of the spring  29  to such an extent that it no longer engages in the recess  25 . To be able to completely pull out the shoulder stock  1  to remove it, the marksman must also release the lock on the slide rail  3   a  by the catch lever  11  in the manner described above. 
     Unlike the catch lever  11 , the securing lever  15  does not project out of the gun casing, so that the marksman cannot grip it by hand. Although the securing lever  15  is accessible from the outside through a slot-like opening  27  in the end plate  9 , this opening  27  is preferably too narrow to allow the marksman to reach in it with his fingers. This prevents accidental release of the securing lever  15 . Nevertheless, it is easy to intentionally release the securing lever  15  because the marksman can press it upward by using any pointed tool. The point of action for that is a notch-like recess  15   a  on the lower side of the securing lever  15  (see FIG.  2 ). 
     FIG. 3 shows a partial, sectional diagram of another shoulder stock  1 ′ constructed in accordance with the teachings of the invention and shown in the resting position. The shoulder stock  1 ′ is secured in this resting position by a catch lever  11 ′ which is rotatably mounted on a pin  17 ′. The design and functioning of this shoulder stock  1 ′ correspond largely to that of shoulder stock  1  described above. Therefore, parts having the same function are provided with the same reference notation, but with apostrophes added for the purpose of differentiating them. 
     The primary difference between shoulder stocks  1  and  1 ′ is that the shoulder cap  5 ′ of the shoulder stock  1 ′ has a blind hole  31 . A spring  33  is mounted in the blind hole  31 . The spring  33  is supported against a pin  35 . The pin  35 , which is displaceably mounted in the blind hole  31 , has on its rear end a shoulder. The front end passes from the pin  35  through an intermediate plate  37  which is mounted on the shoulder cap  5 ′. In the resting position of the shoulder stock  1 ′ shown here, the spring  33  is compressed so that it exerts a force on the end plate  9 ′ (or the shoulder cap  5 ′) by way of the pin  35 . This force tends to move the shoulder stock  1 ′ to the right in FIG. 3 out of its resting position. If the safety on the shoulder stock  1 ′ is lifted by operating the catch lever  11 ′ (as is the case with the shoulder stock  1 ), the spring  33  presses the shoulder cap  5 ′ and intermediate plate  37  downward over the pin  35 . The shoulder stock  1 ′ is, thus, automatically moved out of its resting position by the spring  33  upon operation of the catch lever  11 ′. When so released, the rear shoulder runs toward and into engagement with the intermediate plate  37 . With the shoulder stock  1 ′ shown here, this corresponds to a distance of approx. 2 mm. 
     This automatic movement of the shoulder stock  1 ′ out of its resting position has the advantage that the marksman need not pull the shoulder cap  5 ′ downward at the same time when releasing the catch lever  11 ′. One-handed operation of the shoulder stock  1 ′ is, thus, readily possible in this way. In addition, this prevents the marksman from making operation of the catch lever  11 ′ more difficult for himself due to excessive pulling on the shoulder cap  5 ′. 
     It would be possible to design the locking element of the shoulder stock described in German Patent 1,225,517 to be smaller, and to make it lighter and more space-saving due to the altered proportions. Additional weight could also be saved by using lighter materials. 
     However, the shoulder stocks  1 ,  1 ′ disclosed herein pursue a different option. The locking element  11  illustrated in this patent can be gripped directly by the hand from the outside and turned, in particular even when mounted in the interior of the gun casing. Intermediate elements such as the operating ring mentioned in the background section above are, thus, eliminated. The axis of rotation of the locking element  11  is preferably arranged in the longitudinal direction of the handgun. 
     Persons of ordinary skill in the art will appreciate that the illustrated shoulder stocks  1 ,  1 ′ have (a) at least one slide rail  3   a ,  3   b  which is displaceable together with the shoulder stock  1 ,  1 ′ relative to the gun casing; and (b) at least one catch lever  11 ,  11 ′ which is mounted to rotate about the longitudinal axis of the handgun and which can be directly manually engaged over its outer periphery. The slide rail is lockable by means of the catch lever  11 ,  11 ′ in that the catch lever  11 ,  11 ′ engages in a corresponding recess  13   a ,  13   b ,  23   a ,  23   b  on the slide rail  3   a ,  3   b  thereby securing the shoulder stock in the corresponding position. 
     The term “slide rail” as used here is intended to refer to any type of guide element suitable for displaceably connecting the shoulder stock  1 ,  1 ′ to the gun casing. It is preferably a tubular or rod-shaped body having any desired cross-sectional shape which is displaceably mounted in a corresponding recess or indentation on the gun casing. Due to the displaceability of the slide rail  3   a ,  3   b  within its guide in or on the gun casing, the shoulder stock can be pushed in or pulled out. “Manually operable” in this context means that the catch lever  11 ,  11 ′ can be rotated by hand (preferably without the use of a tool), in such a way that the slide rail  3   a ,  3   b  can thereby be selectively locked to prevent its displacement or released to make it displaceable again. By locking the slide rail to prevent its displacement, the shoulder stock  1 ,  1 ′ attached thereto is secured in the corresponding position. 
     The catch lever  11 ,  11 ′ can be operated by its outer periphery. The outer periphery is referenced to the axis of rotation of the catch lever  11 ,  11 ′ and represents its periphery. It is not necessary for the catch lever  11 ,  11 ′ to be grippable on its entire outer periphery but, instead, it is preferable that only a portion of it is gripped for turning the lever  11 ,  11 ′. The catch lever  11 ,  11 ′ is operated directly by way of the outer periphery (i.e., it can be directly engaged and the engaged surface is secured to the catch lever  11 ,  11 ′ which engages in the recess  13   a ,  13   b ,  23   a ,  23   b  in the slide rail  3   a ,  3   b ). 
     The slide rail  3   a ,  3   b  is locked to prevent its displacement in that the catch lever  11 ,  11 ′ engages in a corresponding recess  13   a ,  13   b ,  23   a ,  23   b  on the slide rail  3   a ,  3   b  through its rotational movement. The axis of rotation of the catch lever  11 ,  11 ′ preferably extends in the longitudinal direction of the handgun, so that the catch lever  11 ,  11 ′ is mounted to rotate across the longitudinal direction of the gun. Depending on the geometry of the gun, however, it may also be advantageous to arrange the axis of rotation in a different direction. 
     Preferably, the catch lever  11 ,  11 ′ is spring loaded in the direction of rotation intended for locking so that it is in contact with the slide rail  3   a ,  3   b  under pressure. Handling of the shoulder stock  1 ,  1 ′ is simple in this case because the catch lever  11 ,  11 ′ need be only operated manually to release the lock, while locking the slide rail  3   a ,  3   b  again takes place automatically due to the load of the spring  19 . The catch lever  11 ,  11 ′ engages automatically in a recess  13   a ,  13   b ,  23   a ,  23   b  when it passes over it. 
     The catch lever  11 ,  11 ′ and the recesses  13   a ,  13   b ,  23   a ,  23   b  in the slide rail  3   a ,  3   b  may have any desired design. Preferably, the catch lever  11 ,  11 ′ is a counterpart to the recesses  13   a ,  13   b ,  23   a ,  23   b  suitable for locking the slide rail  3   a ,  3   b . The recesses  13   a ,  13   b ,  23   a ,  23   b  are preferably designed so that it passes through the slide rail  3   a ,  3   b  in the transverse direction of the handgun. This is advantageous for the case when the catch lever  11 ,  11 ′ is mounted to rotate across the longitudinal direction of the gun, as described above. The catch lever  11   11 ′ can then engage in the recess  13   a ,  13   b ,  23   a ,  23   b  so that it is in contact with the slide rail  3   a ,  3   b  over its entire width. In a preferred embodiment, the catch lever is mounted in the radial direction to its axis of rotation so that its outer periphery extends beyond the end of the recess in this direction. The lengthened part of the outer periphery then projects laterally over the slide rail  3   a ,  3   b  and presents a good contact surface for manual operation by the marksman. If necessary, the outer periphery may also be lengthened to the extent that it projects laterally out of the gun casing. 
     For the easiest possible operation of the catch lever  11 ,  11 ′, it is advantageous, regardless of the alignment of its axis of rotation, if the catch lever  11 ,  11 ′ has a handle, such as a trough-like recess or a nose-shaped projection to be gripped by the marksman. Therefore, the outer periphery of the catch lever  11 ,  11 ′ preferably forms such a handle  11   d  in at least one area. 
     When the gun is not in use or is being transported, it is advantageous if the shoulder stock  1 ,  1 ′ can be inserted as far as the end plate  9  of the gun casing, preferably in such a way that plates  5  and  9  are in contact with one another. This position is referred to herein as the “resting position.” To use the gun, the shoulder stock  1 ,  1 ′ is pulled out of its resting position and into a position in which shooting is possible, with the weapon resting on the shoulder for taking aim (referred to herein as the “use position”). With many guns, it is sufficient to provide for one resting position and one use position. However, it may also be expedient to provide multiple use positions (e.g., to take into account different arm lengths of different marksmen). Then additional recesses are provided on the slide rail  3   a ,  3   b  at corresponding locations to secure the shoulder stock  1 ,  1 ′ in the various use positions. The shoulder stock  1 ,  1 ′ can, thus, be adjusted to different lengths. 
     The slide rail  3   a ,  3   b  thus preferably has at least two recesses such that the shoulder stock can be secured in one resting position and in at least one use position. The shoulder stock  1 ′ is preferably spring loaded in its resting position, with the spring  33  attempting to push the shoulder stock  1 ′ out of its resting position in the direction of the at least of one use position. This causes the shoulder stock  1 ′ to move automatically out of its resting position as soon as the lock on the slide rail  3   a ,  3   b  has been cancelled by appropriate operation of the catch lever  11 ′. In this way, it is easier for the marksman to pull out the shoulder stock  1 ′, because then he need not pull on the shoulder stock  1 ′ at the same time as he is operating the catch lever  11 ′. 
     Starting from a simple design of the shoulder stock  1 ,  1 ′ with a slide rail  3   a  and a catch lever  11 ,  11 ′, the shoulder stock  1 ,  1 ′ can be refined further, depending on the intended purpose. An arrangement with two slide rails  3   a ,  3   b , both of which can be locked by a single catch lever  11 , has proven especially advantageous. Through this arrangement, it is readily possible to unlock the shoulder stock  1 ,  1 ′ with one hand. The axis of rotation of the catch lever  11 ,  11 ′ is preferably arranged between the two slide rails  3   a ,  3   b , preferably in the longitudinal direction of the gun, with the catch lever  11 ,  11 ′ being designed so that it is In contact with the top side of the first slide rail  3   a  and at the same time is in contact with the bottom side of the second slide rail  3   b . For locking the two slide rails  3   a ,  3   b , the catch lever  11 ,  11 ′ then engages in corresponding recesses  13   a ,  13   b ,  23   a ,  23   b  on the top and bottom sides of the slide rails  3   a ,  3   b . In this crossed arrangement, the catch lever  11 ,  11 ′ is preferably spring loaded, so that the slide rails  3   a ,  3   b  are under tension toward one another and toward their guide in the gun casing. The stability of the shoulder stock  1 ,  1 ′ is therefore enhanced, so that it is possible to deliver a well-aimed shot. In addition, the shoulder stock  1 ,  1 ′ is then spring loaded on two sides, namely at the top and bottom. This reduces the risk that the shoulder stock  1 ,  1 ′ might be knocked out of its locked position due to strikes or impacts (e.g., when the marksman is moving over impassable terrain). 
     In the crossed arrangement, the catch lever  11 ,  11 ′ and/or the recesses  13   a ,  13   b ,  23   a ,  23   b  are preferably designed so that the slide rails  3   a ,  3   b  are under tension in the radial direction to the axis of rotation of the catch lever  11 ,  11 ′ when the catch lever  11 ,  11 ′ engages in the recesses  13   a ,  13   b ,  23   a ,  23   b . This further increases the stability of the shoulder stock  1 ,  1 ′ and can be achieved, for example, by the fact that the recesses  13   a ,  13   b ,  23   a ,  23   b  have inclined faces against which the spring-loaded catch lever  11 ,  11 ′ presses. Depending on whether the inclined faces are located on the inside or outside of the slide rails  3   a ,  3   b , they are then pressed in the direction toward one another or apart from one another. 
     As described previously, the shoulder stock  1 ,  1 ′ is released manually by the marksman when he turns the catch lever  11 ,  11 ′ so that it no longer engages in the corresponding recess(es)  13   a ,  13   b ,  23   a ,  23   b  in the slide rail(s)  3   a ,  3   b . The shoulder stock  1 ,  1 ′ can then be shifted. If the stock  1 ,  1 ′ holds the catch lever  11 ,  11 ′ in its twisted (i.e., disengaged) position, it cannot engage in the next recess(es)  13   a ,  13   b ,  23   a ,  23   b  (even if it is spring loaded). In this way, it may happen under some circumstances that the marksman unintentionally pulls the shoulder stock  1 ,  1 ′ completely out of its guide in the gun casing. This may be prevented, for example, by an elevated shoulder on the end of the slide rail  3   a ,  3   b  against which the catch lever  11 ,  11 ′ strikes even in its twisted (i.e., disengaged) position. However, a spring-loaded safety element  15  is provided as the preferred antidote here. This safety element  15  automatically engages in a recess  25  in the slide rail  3   b  which is provided for this purpose when the shoulder stock  1 ,  1 ′ is pulled out. The shoulder stock  1 ,  1 ′ is, thus, secured in its extreme withdrawn position in the same way or at least almost in the same way as it is by the catch lever  11 ,  11 ′, and it cannot be pulled out further. If necessary, the safety element  15  may be designed so that it engages in multiple recesses on one or more slide rails  3   a ,  3   b  at the same time. 
     The safety element  15  limits the displacement of the shoulder stock  1 ,  1 ′ preferably to its outer use position (i.e., in the use position in which the shoulder stock is pulled out to the maximum extent). The marksman can then additionally secure the shoulder stock  1 ,  1 ′ by means of the catch lever  11 ,  11 ′ by turning it back into the engaged position or by simply releasing the catch lever  11 ,  11 ′ if it is spring-loaded. To simplify the renewed insertion of the shoulder stock  1 ,  1 ′ as much as possible, it is advantageous if the safety element  15  need not be released for this purpose. The safety element  15  and/or the respective recess(es)  25  are, therefore, preferably designed so that insertion of the shoulder stock  1 ,  1 ′ is not prevented by the safety element  15 . 
     To make it possible to remove the shoulder stock  1 ,  1 ′ without any great effort despite the safety element  15 , the safety element  15  can preferably be released manually by the marksman in such a way that the lock on the slide rail  3   b  is released. The shoulder stock  1 ,  1 ′ can, thus, be removed easily by the marksman in case of need (e.g., if it interferes with the shooting process due to damage during battle). A tool is preferably needed to release the safety element  15  so as to prevent unintentional removal of the shoulder stock  1 ,  1 ′. 
     For a compact design of the gun, it is advantageous if the catch lever  11 ,  11 ′, and optionally also the safety element  15 , are accommodated in the interior of the gun casing. These are, therefore, preferably an integral part of the end plate  9  of the gun casing. 
     The statements made above regarding the shoulder stock  1 ,  1 ′ also apply accordingly for the catch lever  11 ,  11 ′ and its advantageous embodiments. 
     Although certain apparatus constructed in accordance with the teachings of the invention have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all embodiments of the teachings of the invention fairly failing within the scope of the appended claims either literally or under the doctrine of equivalents.