Patent Publication Number: US-10760875-B2

Title: Replacement buttstock for rifle

Description:
NOTICE OF COPYRIGHT 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to any reproduction by anyone of the patent disclosure, as it appears in the United States Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND OF THE PRESENT INVENTION 
     Field of Invention 
     The present invention relates to a buttstock for a gun, and more particularly to a replacement buttstock which is adapted for being easy to assembly with and detach from a rifle. 
     Description of Related Arts 
     A buttstock, which is also known as a shoulder stock, a stock or a butt, is a rear part of a rifle. During usage, the buttstock is held to bias against a user&#39;s shoulder, so that the backlash vibration generated in a shooting operation can be evenly transmitted to the user&#39;s body, and thus the user&#39;s body will not be easy to get hurt in the backlash movement of the rifle. In addition, since the buttstock provides a support to the rifle, it also enhances the stability when aiming and shooting, so as to increase the shooting accuracy. 
     The buttstock can be a fixed part of the rifle, but a collapsible buttstock is more comfortable to use. It has the ability to be used as a long, fixed stock for controlled, accurate firing. It also can be adjusted to fit the individual shooters, thus making the shooter as comfortable as possible when shooting. When in not use, the collapsible buttstock can be disassembled from the rifle, so that the total length of the firearm is reduced, and the rifle is easier to store when the user is travelling. What&#39;s more, a collapsible buttstock can be assembled with a new rifle, helping the user to save costs. In other words, the user may create a collection of different types of rifles which can be detachably assembled with the same collapsible buttstock. 
     However, the conventional collapsible buttstock is not convenient to assemble or disassemble, it is time and effort consuming before the shooter is ready for shooting.  FIG. 1  of the drawings shows a typical conventional collapsible buttstock which includes a butt body  1  and a locking lever arrangement  2 . When removing the collapsible buttstock from a rifle having a connecting barrel  3 , the user has to use one hand to hold firmly to an upper portion of the rifle, and then use another hand to grasp the entire locking lever arrangement and pull it away from the butt body so as to fully retract the lever lock pin which has been inserted into a chamber of the butt body  1  for locking the connecting barrel  3 , and then sliding the buttstock backward to disengage with the barrel of the rifle. To install the collapsible buttstock, similarly, the user has to use one hand to hold firmly to the upper portion of the rifle, and then use another hand to pull the locking lever arrangement  2  away from the butt body  1  for enabling the connecting barrel  3  to slide into the chamber of the butt body  1 . Actually, the removal or installation of the collapsible buttstock requires a great effort in the pulling and pressing process, so that it is often accomplished by fixing the rifle in a gunsmith&#39;s rifle vice or fixture. In an alternative mode of the conventional firearm with the rifle and the collapsible buttstock, the user may have to user two hands to operate on the lock lever arrangement  2 . For example, the user has to use fingers of two hands to press an end of the lock lever arrangement  2  to an utmost position for displacing the lock lever pin. 
     It is thus can be seen that the conventional collapsible buttstock is disadvantageous in that the user cannot quickly the remove or install the conventional collapsible buttstock during usage. Particularly, when a user is holding on the rifle with a desired aiming gesture, he or she has to change his or her original holding gesture if he or she wants to assemble or disassemble the buttstock. For example, when the user uses his or her two hands to hold on the rifle in a desired ready to shoot position, if he or she wants to install the collapsible buttstock on the rifle, he or she has to move one hand which is holding on a clip at a bottom side of the rifle to a position holding the upper side of the rifle and simultaneously use the other hand to operate on the locking lever arrangement  2  for allowing the connecting barrel  3  to be inserted into the chamber of the butt body  1 , and then the user needs an additional step for adjusting his or her hands to find the desired holding position for shooting. Otherwise, if the user wants to maintain the holding position of his or her right hand on the clip of the rifle and use another hand to pull the locking lever arrangement  2 , the pulling force will actually tend to drive the buttstock to rotate with respect to the holding position of his or her right hand on the rifle, and thus resulting in a failure for pulling out the locking lever pin of the locking lever arrangement  2 . As another example, when the user is holding on the rifle and aiming at a desired shooting direction, but there is a limited room and space for the shooter to hide the rifle and to hide himself or herself, it is impossible for him or her to remove the collapsible buttock while maintaining the holding position and the shooting direction. In addition, in a situation requires a quick shooting response, the user cannot immediately use one hand to adjust the aiming position while simultaneously use anther hand to assemble the collapsible buttstock to the rifle, instead, he or she has to install the buttstock on the rifle with his or her two hands before aiming and shooting. 
     SUMMARY OF THE PRESENT INVENTION 
     The invention is advantageous in that it provides a replacement buttstock for rifle, wherein the replacement buttstock is convenient and easy to be quickly assembled with and detached from the rifle. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein a user does not have to change his or her original holding gesture if he or she wants to assemble or disassemble the replacement buttstock while holding on the rifle with a maintained aiming gesture. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein the user is capable of quickly getting ready for shooting by adjusting the holding position and gesture of the rifle while simultaneously assemble the replacement buttstock with the rifle. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein it only requires a single hand of the user to operate on a locking lever assembly of the replacement buttstock for enabling a connecting extension of the rifle to be inserted into or slid out from a receiving chamber of the replacement buttstock. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein unlike the pulling mechanism of the conventional collapsible buttstock for vertically moving the locking lever arrangement, only a convenient operation on the locking lever assembly with a relatively few effort is required for enabling a rotating movement of a lever element of the locking lever assembly for displacing a locking pin so as to release the connecting extension of the rifle. 
     Another advantage of the invention is to provide a replacement buttstock for rifle which enables the user to use his or her different fingers of a single hand to cooperatively operate on the lever element and a stopper element of the locking lever assembly respectively for assembling or disassembling the rifle with the replacement buttstock. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein the user only has to press or pull the stopper element for providing a moving space for the lever element and a press operation on a proximal end portion of the lever element of the locking lever assembly of the replacement buttstock will enable a rotating movement of the lever element for driving the locking pin at a distal end portion of the lever element to move into or get out from the receiving chamber of the replacement buttstock so as to slid in or slide out the connecting extension of the rifle for assembling or disassembling the replacement buttstock with the rifle. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein the locking lever assembly can be operated for disengaging the locking pin with the connecting extension so as to adjust the engaging position of the connecting extension with the locking pin for fitting the individual shooters by adjusting a distance between the rifle and a shoulder of the shooter, thus making the shooter feel comfortable when shooting. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein when pressing on the lever element of the locking lever assembly for adjusting the assembling position of the connecting extension of the rifle, the stopper element prevents the further movement of the lever element so as to prevent the connecting extension of the rifle from sliding out from the receiving chamber of the replacement buttstock. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein after the operation on the locking lever assembly for assembling or disassembling the replacement buttstock with the rifle, the locking lever assembly will automatically restore its original position immediately after the user releases his or her hand on the locking lever assembly. 
     Another advantage of the invention is to provide a replacement buttstock for rifle, wherein the structure of the replacement buttstock is not complicated and also is easy for manufacturing to save costs. 
     Additional advantages and features of the invention will become apparent from the description which follows, and may be realized by means of the instrumentalities and combinations particularly pointing out in the appended claims. 
     According to the present invention, the foregoing and other objects and advantages are attained by a replacement buttstock for a rifle including a connecting extension, wherein the replacement buttstock comprises a stock body and a locking lever assembly coupled to the stock body. The stock body has an elongated receiving chamber for receiving a connecting extension of a rifle. The locking lever assembly includes a lever element, a locking pin connected to the lever element for retaining the connecting extension in the receiving chamber of the stock body, a stopper element arranged for being operated to allow the lever element which is being pressed to move to an unlock state in which the locking pin is driven to move out of the receiving chamber of the stock body by the lever element for unlocking the connecting extension and a restoring element restoring element for restoring the lever element when the lever element is released. 
     The present invention further provides a method for assembling a replacement buttstock with a rifle including a connecting extension, wherein the method comprises the following steps. 
     (a) Displace a stopper element for allowing a movement of a lever element when the stopper element is operated. 
     (b) Drive an engaging end portion of a locking pin to move out of a receiving chamber of a stock body by the lever element when the lever element is pressed. 
     (c) Receive the connecting extension of the rifle in the receiving chamber of the stock body. 
     (d) Restore the stopper element and the lever element to insert the engaging end portion of the locking pin into the receiving chamber of the stock body and retain the connecting extension of the rifle in the receiving chamber of the stock body by the locking pin when the stopper element and the lever element is released. 
     The present invention further provides a method for disassembling a replacement buttstock with a rifle including a connecting extension, wherein the method comprises the following steps. 
     (A) Displace a stopper element for allowing a movement of a lever element when the stopper element is operated. 
     (B) Drive the engaging end portion of the locking pin to move out of a receiving chamber of a stock body when the lever element is pressed. 
     (C) Disengage a locking pin with the connecting extension of the rifle for allowing the connecting extension of the rifle to be slid out of the receiving chamber of the stock body. 
     The present invention further provides a method for adjusting an assembling position of a connecting extension of a rifle in a receiving chamber of a stock body of a replacement buttstock, wherein the method comprises the following steps. 
     (α) Disengage a locking pin with a first retaining groove of the connecting extension of the rifle which is received in the receiving chamber of the stock body in a first assembling position when a lever element is moved to displace the locking pin. 
     (β) Stop a further movement of the lever element by a stopper element for preventing the locking pin to be moved out of the receiving chamber of the stock body. 
     (γ) Engage the locking pin with a second retaining groove of the connecting extension of the rifle by restoring the lever element to reposition the locking pin after the connecting extension of the rifle is slid in the receiving chamber of the stock body to a second assembling position which aligns the locking pin with the second retaining groove of the connecting extension of the rifle. 
     Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
     These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating a conventional collapsible buttstock. 
         FIG. 2  is a perspective view of a replacement buttstock according to a first preferred embodiment of the present invention 
         FIG. 3A  is a side view of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 3B  is a front view of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 4  is an exploded view of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 5A  is a perspective view of a locking lever assembly of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 5B  is a sectional view along line A-A of  FIG. 5A . 
         FIG. 5C  is a schematic view illustrating a bottom structure of a stock body for engaging with the locking lever assembly of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIGS. 6A and 6B  are different perspective views of a lever element of a locking lever assembly of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 7A  is a bottom view of the lever element of the locking lever assembly of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 7B  is a sectional view along line B-B of  FIG. 6A . 
         FIGS. 8A, 8B and 8C  are schematic views illustrating a stopper element of the locking lever assembly of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 9A  is a schematic view illustrating a rifle being assembled with replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 9B  is an enlarged perspective view of a connecting extension of the rifle for being engaged with the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 9C  is a sectional view along line C-C of  FIG. 9B . 
         FIG. 10  is a schematic view illustrating the connecting extension being assembled with the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIGS. 11A, 11B, 11C and 11D  are schematic views illustrating the operation on the lever element for adjusting the engaging position of the connecting extension with a locking pin of the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIGS. 12A, 12B, 12C, 12D, 12E and 12F  are schematic views illustrating the operation on the stopper element and the lever element of the locking lever assembly for inserting the connecting extension of the rifle into the replacement buttstock or pull the connecting extension of the rifle out of the replacement buttstock for assembling or disassembling the rifle with the replacement buttstock according to the above first preferred embodiment of the present invention. 
         FIG. 13  is a perspective view of a replacement buttstock according to a second preferred embodiment of the present invention. 
         FIG. 14  is an exploded view of the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIG. 15  is a perspective view of a stopper element of the locking lever assembly of the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIG. 16  is a perspective view of the assembled locking lever assembly of the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIG. 17  is a schematic view illustrating a connecting extension being engaged with replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIGS. 18A and 18B  are schematic views illustrating the operation on the lever element for adjusting the engaging position of the connecting extension with a locking pin of the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIGS. 19A, 19B, and 19C  are schematic views illustrating the operation on the stopper element and the lever element of the locking lever assembly for inserting the connecting extension of the rifle into the replacement buttstock or pull the connecting extension of the rifle out of the replacement buttstock for assembling or disassembling the rifle with the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIG. 20  is a perspective view of a replacement buttstock according to an alternative mode of the above second preferred embodiment of the present invention. 
         FIG. 21  is an exploded view of the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIG. 22  is a schematic view illustrating a connecting extension being engaged with replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIGS. 23A and 23B  are schematic views illustrating the operation on the lever element for adjusting the engaging position of the connecting extension with a locking pin of the replacement buttstock according to the above second preferred embodiment of the present invention. 
         FIGS. 24A, 24B, and 24C  are schematic views illustrating the operation on the stopper element and the lever element of the locking lever assembly for inserting the connecting extension of the rifle into the replacement buttstock or pull the connecting extension of the rifle out of the replacement buttstock for assembling or disassembling the rifle with the replacement buttstock according to the above second preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description is disclosed to enable any person skilled in the art to make and use the present invention. Preferred embodiments are provided in the following description only as examples and modifications will be apparent to those skilled in the art. The general principles defined in the following description would be applied to other embodiments, alternatives, modifications, equivalents, and applications without departing from the spirit and scope of the present invention. 
     Those skilled in the art should understand that, in the disclosure of the present invention, terminologies of “longitudinal,” “lateral,” “upper,” “front,” “back,” “left,” “right,” “perpendicular,” “horizontal,” “top,” “bottom,” “inner,” “outer,” and etc. that indicate relations of directions or positions are based on the relations of directions or positions shown in the appended drawings, which are only to facilitate descriptions of the present invention and to simplify the descriptions, rather than to indicate or imply that the referred device or element is limited to the specific direction or to be operated or configured in the specific direction. Therefore, the above-mentioned terminologies shall not be interpreted as confine to the present invention. 
     Referring to  FIG. 1  to  FIG. 12F  of the drawings, a replacement buttstock  100  according to a first preferred embodiment of the present invention is illustrated. The replacement buttstock  100  of this preferred embodiment comprises a stock body  10 , a locking lever assembly  20  coupled to the stock body  10 , and a stock pad  30  connected to the stock body  10 . The replacement buttstock  100  is adapted for being assembled with or disassembled with a rifle  40  which comprises a rifle body  41  and a connecting extension  42  connected the rifle body  41  for detachably coupling with the replacement buttstock  100 . The connecting extension  42  can be integrally extended from the rifle body  41  or is installed with the rifle body  41 , as is shown if  FIG. 9A  of the drawings. 
     The rifle  40  of the present invention, which is a typical portable long-barrelled firearm designed for precision shooting, is to be held with both hands and braced against a shoulder of a user with the aid of the replacement buttstock  100  for stability during firing and shooting. The rifle  40  can be a firearm used in warfare, hunting and shooting sports, or is just a toy gun for entertainment of the user. 
     The stock body  10  has an elongated receiving chamber  101  at an upper side thereof for engaging with the connecting extension  42  of the rifle  40 , the locking lever assembly  20  is adapted for being operated to lock or unlock the connecting extension  22  in the receiving chamber  101  of the stock body  10 . The stock pad  30  comprises a pad body  31  and one or more connecting element  32  for connecting the pad body  31  to a rear end portion of the stock body  10 . The pad body  31 , which is preferably made of resilient material such as rubber, is biasing against the shoulder of the user during shooting for evenly distributing the backlash vibration to the shoulder of the user. 
     More specifically, by operation on the locking lever assembly  20 , the connecting extension  42  of the rifle  40  can be inserted into the receiving chamber  101  of the stock body  10  and be retained in the receiving chamber  101  of the stock body  10 , the connecting extension  42  of the rifle  40  is then connected with the stock body  10  so as to assemble the rifle  40  with the replacement buttstock  100 . The connecting extension  42  of the rifle  40  also can be released and pulled out from the receiving chamber  101  of the stock body  10  to disassemble the rifle  40  with the replacement buttstock  10 . 
     The connecting extension  42  of the rifle  40  comprises an elongated extension member  421  which can be a connecting barrel with a hollow structure, and an engaging member  422  integrally extended from or connected to a lower side of the extension member  421 , as is shown in  FIG. 9B  of the drawings. The engaging member  422  has a sliding groove  4221  extended along a length thereof at a lower side of the engaging member  422 , and a plurality of retaining grooves  4222  communicated to the sliding groove  4221 . Accordingly, the engaging member  422  has an inner wall  4223 , two spaced apart side walls  4224 , two end walls which are a proximal end wall  4225  and a distal end wall  4226  extended from the two side walls  4224  to define the sliding groove  4221  therewithin, the plurality of retaining grooves  4222  are disposed in the inner wall  4223 . The person of ordinary skilled in the art should understand that the retaining grooves  4222  may also be disposed in the extension member  421   
     Referring to  FIG. 4  of the drawings, the locking lever assembly  20  comprises a lever element  21 , a stopper element  22  a locking pin  23 , and a restoring element  24 . The locking pin  23  is adapted for engaging with one of the plurality of retaining grooves  4222  for retaining the connecting extension  42  within the receiving chamber  101  of the stock body  10 . The lever element  21  can be pressed to drive the locking pin  23  to move so as to engage or disengage with one of the retaining grooves  4222  for locking or unlocking the connecting extension  42 . More specifically, when the locking pin  23  is engaged with one of the retaining grooves  4222 , by operating on the lever element  21  to drive the locking pin  23  connected to the lever element  21  to disengage with the one of the retaining grooves  4222 , and then the connecting extension  42  can be slid in the receiving chamber  101  of the stock body  10  for adjusting the assembling position of the connecting extension  42 , and the connecting extension  42  can be retained in the receiving chamber  101  of the stock body  10  by engaging the locking pin  23  with another retaining groove  4222 . It is still worth mentioning that in an alternative example, a retaining groove  4222  may be formed in the locking pin  23 , while the connecting extension  42  may be formed with a plurality of positioning protrusions for engaging with the retaining groove  4222  in the locking pin  23  for locking the connecting extension  42  in the receiving chamber  101  of the stock body  10 . 
     It is worth mentioning that when only the lever element  21  is operated, the stopper element  22  is retained at its original position for stopping the further movement of the lever element  21  for preventing the locking pin  23  to be moved to a position allowing the connecting extension to be inserted into or slide out from the receiving chamber  101  of the stock body  10 . In other words, when the stopper element is not moved, the lever element  21  can be moved to displace the locking pin  23  so as to allow the connecting extension  42  to slide in the receiving chamber  101  of the stock body  10  but cannot slide out from the receiving chamber  101  of the stock body  10 . When both the stopper element  22  and the lever element  21  are moved, the locking pin  23  will not block the sliding movement of the connecting extension  42  so as to enable the connecting extension  42  to be inserted into or slide out from the receiving chamber  101  of the stock body  10 , the mechanism will be discussed in detail in the following description. 
     The receiving chamber  101  of the stock body  10  has an upper accommodation chamber  1011  and a lower sliding chamber  1012  communicated with the upper accommodation chamber  1011 , as is shown in  FIG. 3  and  FIG. 4  of the drawings. The accommodation chamber  1011  is sized and shaped to match with the extension member  421  of the connecting extension  42  while the sliding chamber  1012  is sized and shaped to match with the engaging member  422  of the connecting extension  42 . Accordingly, the engaging ember  422  is capable of being slid in the sliding chamber  102  for adjusting the engaging position between the locking pin  23  and the retaining grooves  4222 . 
     The lever element  21  has a proximal end portion  2101  and a distal end portion  2102 , and the locking pin  23  is coupled to the distal end portion  2102  for engaging with one of the retaining grooves  4222  of the engaging member  42 . When the proximal end portion  2101  of the lever element  21  is pressed, the locking pin  23  at the distal end portion  2102  of the lever element  21  can be actuated to move simultaneously. 
     The locking pin  23  comprises a pin body  231 , a connector  232 , and a fixing element  233 . The lever element  21  comprises a base plate  211 , and two mounting walls  212  extended from the base plate  211  respectively. The base plate  211  has a penetrating hole  2111 , each of the two mounting walls  212  has a mounting hole  2121 , the pin body  231  has an upper engaging end portion  2311  which is capable of being inserted into the sliding chamber  1012  and the sliding groove  4221 , and can be further driven to be inserted into one of the retaining grooves  4222  for locking the connecting extension  42 . The pin body  231  has a connecting hole  2312  at a lower portion thereof for the connector  232 , which is retained at a position corresponding to the mounting holes  2121  of the two mounting walls  212 , to penetrate therethrough for connecting the locking pin  23  with the lever element  21 . The fixing element  233 , which can be embodied as a stopping screw, is to firmly retain the connector  232  at the pin body  231  to enhance the connection therebetween. The bottom penetrating hole  2111  is formed for facilitating the assembling process of the connector  232 . 
     Referring to  FIGS. 4 to 6B  of the drawings, the lever element  21  further comprises a rotation axle  213  and a pair of fixing members  214  for fixing the rotation axle  213  with the stock body  10 . The lever element  21  is capable of rotating with respect to the rotation axle  231  which is located at a middle portion of the lever element  21 . Accordingly, when the proximal end portion  2101  of the lever element  21  is pressed, the lever element  21  will rotate with respect to the rotation axle  231  to drive the pin body  231  of the locking pin  23  to disengage with the corresponding retaining groove  422 , so that the connecting extension  42  of the rifle can be slid in the receiving chamber  101  of the stock body  10  by sliding the extension member  421  in the accommodation chamber  1011  and simultaneously sliding the engaging member  422  in the sliding chamber  1012 , so as to align another retaining groove  4222  with the pin body  231  of the locking pin  23  and engage the another retaining groove  422  with the pin body  231  of the locking pin  23  for adjusting the assembling position of the connecting extension  42  with the replacement buttstock, thus adjusting a distance between a user&#39;s shoulder and the rifle  40  for enabling the user to find a comfortable holding gesture for the rifle  40 . 
     It is worth mentioning that the stock body  10  comprises a receiving portion  11  defining the receiving chamber  101 , and a mounting portion  12  extended at a bottom of the receiving portion  11  for mounting the locking lever assembly  20 . The receiving portion  11  has a base inner wall  111  and a surrounding inner wall  112  defining the receiving chamber  101 . Accordingly, when the proximal end portion  2101  of the lever element  21  is pressed, the lever element  21  will rotate with respect to the rotation axle  231  to drive the pin body  231  of the locking pin  23  to disengage with the corresponding retaining groove  422 , but at the same time, the engaging end portion  2311  of the pin body  231  of the locking pin  23  is still penetrated and protruded from the base inner wall  111  of the receiving portion  11  of the stock body  10  and is extending in the sliding groove  4221  of the engaging member  422 , so that the engaging end portion  2311  of the pin body  231  of the locking pin  23  can only be slid in the sliding groove  4221  of the engaging member  422  within the sliding chamber  1012  of the stock body  10 , the proximal end wall  4225  and the distal end wall  4226  of the engaging member  422  will block the further sliding movement of the pin body  231  of the locking pin  23  in the sliding groove  4221  of the engaging member  422  for restricting the sliding path of the pin body  231  of the locking pin  23 . Accordingly, the pin body  231  of the locking pin  23  is slid in the sliding groove  4221  of the engaging member  422  and can be biasing against the proximal end wall  4225  of the engaging member  422  to block the sliding movement of the connecting extension  42  of the rifle  40  in the receiving chamber  101  of the stock body  10  for preventing the connecting extension  42  of the rifle  40  to slide out from the receiving chamber  101  of the stock body  10 . 
     When the lever element  21  is pressed to drive the locking pin  23  to produce a displacement, the restoring element  24  is deformed to generate a restoring energy, and when the lever element  21  is released, the restoring energy of the restoring element  24  will drive the lever element  21  to restore its original state. 
     According to this preferred embodiment of the present invention, the restoring element  24  can be a torsion spring, referring to  FIG. 2  of the drawings, the torsion spring is actually embodied as a twins torsion spring comprises two spring coils  241 , two free first biasing legs  242  extended from the two spring coils  241  respectively, and two second biasing legs  243  extended between the two spring coils  241  and are connected with each other to form an integral connecting leg which defines an acute angle with respect to the two free first biasing legs  242 . The rotation axle  213  penetrates through the two spring coils  241 . Accordingly, when the proximal end portion  2101  of the lever element  21  is pressed to drive the lever element  21  to rotate with respect to the rotation axle  213 , the biasing legs  242  and  243  are pressed to reduce the acute angle between the first biasing legs  242  and the second biasing legs  243  to generate a resilient restoring power, and when the lever element  21  is released, the biasing legs  242  and  243  restores their original position to drive the lever element  21  to move to its original state. 
     In addition, in this preferred embodiment, the lever element  21  further comprise a retention member  215  connected between the two mounting walls  212  for fixing and retaining the two first biasing legs  242  in position. 
     As is shown in  FIG. 5C  of the drawings, the mounting portion  12  comprises two side mounting plate  121  each having a side hole  122  at a middle portion thereof, the two side mounting plates  121  are spaced from each other to define an installing groove  123  for mounting the locking lever assembly  20 . Each of the two mounting walls  212  has an installing hole  2122  which is aligned with the side hole  122  of each of the two side mounting plate  121  of the mounting portion  12  of the stock body  10  for each of the fixing member  214  to penetrate therethrough for fixing the rotation axle  213  to the side mounting plate  121  of the mounting portion  12  of the stock body  10 . 
     The mounting portion  12  further has a bottom stopping surface  124  at a bottom side thereof for blocking the movement of the stopper element  22  when only the proximal end portion  2101  of the lever element  21  is pressed. More specifically, when the user uses his or her fingers to press the proximal end portion  2101  of the lever element  21 , the lever element  21  rotates to drive the stopper element which is provided above the base plate  211  of the lever element  21  to simultaneously rotate, but the upward rotating movement of the stopper element  22  will be blocked by the bottom stopping surface  124  of the mounting portion  12 , so that the pin body  231  of the locking pin  23  will be retained in the sliding groove  4221  to prevent the connecting extension  42  from sliding out from the receiving chamber  101  of the stock body  10 . It is worth mentioning that the stopper element  22  may also be mounted to the stock body  10  in an alternative mode. 
     According to this preferred embodiment, in the adjusting process of the assembling position of the connecting extension  42  of the rifle  40 , the stopper element  22  biasing against the bottom stopping surface  124  of the mounting portion  12  of the stock body  10  for retaining the pin body  231  of the locking pin  23  in the sliding groove  4221  of the connecting extension  42  of the rifle  40 . In addition, the stopper element  22  of the instant invention is employed for enabling the assembling or disassembling of the connecting extension  42  of the rifle  40  with the replacement buttstock  100  of the present invention. 
     More specifically, in this preferred embodiment of the present invention, as is shown in  FIG. 5C  of the drawings, the mounting portion  12  of the stock body  10  further has an accommodation groove  125  which is communicated with the installing groove  123  and inwardly indented from the bottom stopping surface  124  for providing an accommodation space allowing the stopper element  22  to be inserted therein. A through hole  126  is formed at a bottom of the stock body  10 , so that the engaging end portion  2311  of the pin body  231  of the locking pin  23  can be inserted into the sliding chamber  1012  of the stock body  10 . 
     Referring to  FIG. 4  and  FIGS. 8A to 8C  of the drawings, the stopper element  22  comprises a stopper body  221  and a reposition member  222  connected to the lever element  21 . In this preferred embodiment, after the stopper body  221  is pushed at a proximal end  2211  thereof to a position which is aligned with the accommodation groove  125 , the pressing operation on the proximal end portion  2101  of the lever element  21  at the bottom side thereof will drive the stopper body  221  to move into the accommodation groove  125  of the mounting portion  12  of the stock body  10 . In other words, when the stopper body  221  is pushed at a proximal end  2211  thereof, the proximal end  2211  of the stopper body  221  is moved to a position beyond an edge of the bottom stopping surface  124  of the stock body  10 , so that the bottom stopping surface  124  of the stock body  10  cannot block the upward rotating movement of the stopper element  121  into the accommodation groove  125  of the mounting portion  12  of the stock body  10 . At that time, the pin body  231  of the locking pin  23  of the locking lever assembly  20  is moved out from the sliding groove  4221  of the connecting extension  42  of the rifle  40  and also is moved out from the sliding chamber  1012  of the stock body  10 , that is to say, the engaging end portion  2311  of the pin body  231  of the locking pin  23  of the locking lever assembly  20  is no longer retained in the sliding groove  4221  of the connecting extension  42  and the sliding chamber  1012  of the stock body  10 , enabling the connecting extension  42  of the rifle  40  to be slid into or slid out of the receiving chamber  101  of the stock body  10  for installing the rifle  40  with the replacement buttstock  100  or remove the replacement buttstock  100  from the rifle  40 , for the pin body  231  of the locking pin  23  will no longer block the sliding movement of the engaging member  422  of the connecting extension  42  of the rifle  40 . 
     Furthermore, when the stopper element  22  and the lever element  21  are released, the reposition member  222  will restore the stopper element  22  to its original position and the restoring element  24  will restore the lever element  21  to its original position. According to this preferred embodiment of the present invention, the reposition member  222  can be embodied as a resilient spring which is connected to the lever element  21 . Accordingly, when the stopper element  22  is pushed at the proximal end  2211 , the resilient spring is compressed, and when the stopper element  22  is released, the resilient spring restores to its original form so as to drive the stopper body  221  to move back to its original position. 
     The lever element  21  of this preferred embodiment further comprises a connecting part  216  which is provided above the base plate  211  of the lever element  21  for connecting with the reposition member  222  of the stopper element  22 . More specifically, the connecting part  216  has a connecting groove  2161  for receiving the reposition member  222  which is a resilient spring and also for restricting the reposition member  22  to move in a linearly movement manner, the reposition member  222  has one end connected to the stopper body  221  and the other opposite end connected to the connecting part  216 . 
     The stopper body  221  of the stopper element  22  has a receiving groove  2212 , two end walls  2213  and two protrusion walls  2214  extended and protruded from the two end walls  2213  respectively. At least a portion of the connecting part  216  of the lever element  21  is disposed in the receiving groove  2212  of the stopper body  221  of the stopper element  22 . Each of the two mounting walls  212  of the lever element  21  forms a seat portion  2124  at a proximal end thereof including an outer seating surface  21241  and an inner seating surface  21242 . It is worth mentioning that when the stopper body  221  of the stopper element  22  is pushed to align with the accommodation groove  125  of the stock body  10 , each of the outer seating surface  21241  of the seat portion  2124  is biasing against the corresponding end wall  2213  of the stopper body  221  and each of the inner seating surface  21242  of the seat portion  2124  is biasing against the corresponding the protrusion wall  2214  of the stopper body  221  to block the further movement of the stopper body  221 . 
     The stopper body  221  may further comprises a restricting member  2215  connected between the two end walls  2213  at a distal end thereof, while the connecting part  215  of the lever element  21  has a restricting wall  2152 . The restricting member  2215  is biasing against the restricting wall  2152  of the connecting part  215  when the locking lever assembly is in the locked state. 
     Accordingly, as shown in  FIG. 12B  of the drawings, when the stopper element  22  is at its original position, there is a slot  217  between each end wall  2213  of the stopper body  221  and the corresponding outer seating surface  21241  and a width of the slot  216  define a moving distance of the stopper body  221  above the base plate  211  of the lever element  21  as well as a compression stroke of the reposition member  222  which is a resilient spring. 
     Referring to  FIGS. 12A to 12F  of the drawings, the replacement buttstock  100  of this preferred embodiment of the instant invention is capable of shifting between three states which are a locking state in which the lever element  21  and the stopper element  22  are all at their original positions while the pin body  231  of the locking pin  23  is retained in one of the retaining grooves  4222  of the connecting extension  42  when the replacement buttstock  100  is assembled with the rifle  40 , an adjusting state in which the lever element  21  is pressed to drive the stopper element  22  move to a position biasing against the bottom stopping surface  124  while the engaging end portion  2311  of the pin body  231  of the locking pin  23  is moved out from the corresponding retaining groove  4222  and is still retained in the sliding groove  4221  so that simply by sliding the connecting extension  42  in the receiving chamber  101  of the stock body  10  is able to align a new retaining groove  4222  with the pin body  231  of the locking pin  23  so that the assembling position of the connecting extension  42  in the stock body  10  is adjusted, and an unlocking state in which the stopper element  22  is longitudinally pushed at an end surface  22111  of the proximal end  2211  of the stopper body  221  of the stopper element  21  to align the stopper body  221  with an accommodation groove  125  of the stock body  10  and the lever element  21  is transversely pressed on the proximal end portion  2101  at a bottom side thereof to drive the stopper body  221  to be moved towards the accommodation groove  125  of the stock body  10  to allow at least a portion of the stopper body  221  to be inserted into the accommodation groove  125  of the stock body  10  while the lever element  21  is also rotated to drive the pin body  231  of the locking pin  23  to be moved away from the sliding groove  4221  of the connecting extension  42  and the sliding chamber  1012  of the stock body  10  so that the locking lever assembly  20  is unlocked so that the connecting extension  42  of the rifle  40  can be convenient to be inserted into the receiving chamber  101  of the stock body  10  or be removed from the receiving chamber  101  of the stock body  10  for assembling or disassembling the rifle  40  with the replacement buttstock  100  respectively. 
     Accordingly, when in the unlocked state, the total stopper element  22  may be inserted into the accommodation groove  125  of the stock body  10  while the lever element  21  is biasing against the bottom stopping surface  124  for preventing the further rotating movement of the lever element  21 . According to this preferred embodiment, a portion of the stopper element  22  is inserted into the accommodation groove  125  of the stock body  10  while the end surface  22111  is biasing against an edge  1241  of the bottom stopping surface  124  for stopping the further movement of the stopper element  22  and the lever element  21 . Accordingly, the end surface  22111  of the proximal end  2211  of the stopper body  221  of the stopper element  21  can be embodied to have a step-like configuration, an inclined surface or an arch surface for engaging with the edge  1241  of the bottom stopping surface  124  of the stock body  10 . The stopper body  221  of the stopper element  21  of this preferred embodiment has one or more retaining slit  22112  in the end surface  22111  of the proximal end  2211  for engaging with the edge  1241  of the bottom stopping surface  124  of the stock body  10  when the locking lever assembly  20  is in the unlocked state. 
     By pushing the stopper element  22 , the proximal end portion  2101  of the lever element  21  is able to move with a larger distance in the unlocked state than in the adjusting state, so that the pin body  231  of the pin  23  can be moved out of the sliding groove  4221  of the connecting extension  42  and the sliding chamber  1012  of the stock body  10 . 
     It is thus can be seen that the replacement buttstock  100  of this preferred embodiment of the present invention is convenient and easy to be quickly installed with and removed from the rifle  40 . The rifle  40  comprises the rifle body  41  including a clip  411 . When a user is holding on the rifle  40  by griping the clip  411  with one hand and has adjusted to a desired aiming gesture, he or she does not have to change the desired aiming gesture if he or she wants to assemble or disassemble the replacement buttstock  100 . Particularly, the user only needs to use his or her another hand to operate on the locking lever assembly  20  for moving the locking pin  23  so that the connecting extension  42  can be easy and convenient to be inserted into or slid out of the receiving chamber  101  of the stock body for quickly assemble or disassemble the rifle  40  with the detachable buttstock  100 , while the hand holding on the clip  411  can be maintained at its original position for maintaining the desired aiming gesture with an original aiming direction. 
     Also, the user is capable of quickly getting ready for shooting by adjusting the holding position of one hand which is held on the clip  411  of the rifle  40  while simultaneously assemble the replacement buttstock  100  with the rifle  40  with the other hand. 
     More specifically, referring to  FIGS. 12A to 12  F of the drawings, the user can use a single hand to operate on a locking lever assembly  20  of the replacement buttstock  100  for enabling the connecting extension  42  of the rifle  40  to be inserted into or slid out from the receiving chamber  101  of the stock body  10 . He or she can use his or her thumb to push the stopper element  22  at the proximal end  221  thereof and use one or more fingers to press the lever element  21  on the proximal end portion  2101  at a bottom side thereof for moving the locking lever assembly  20  to the unlocked state. 
     Accordingly, this first preferred embodiment of the present invention provides a method for assembling the replacement buttstock  100  with the rifle  40  including the connecting extension  42 , wherein the method comprises the following steps: 
     (a) displacing the stopper element  22  for allowing a movement of the lever element  21  when the stopper element  22  is operated by the user such as by pushing the stopper element  22  at the proximal end  2211  thereof; 
     (b) driving the engaging end portion  2311  of the locking pin  23  to move out of the receiving chamber  101  of the stock body  10  by the lever element  21  when the lever element  21  is pressed by the user; 
     (c) receiving the connecting extension  42  of the rifle  40  in the receiving chamber  101  of the stock body  10 ; and 
     (d) restoring the stopper element  22  and the lever element  21  to insert the engaging end portion  2311  of the locking pin  23  into the receiving chamber  101  of the stock body  10  and retaining the connecting extension  42  of the rifle  40  in the receiving chamber  101  of the stock body  10  by the locking pin  23  when the locking lever assembly  20  is released by the user. 
     Accordingly, this first preferred embodiment of the present invention provides a method for disassembling the replacement buttstock  100  with the rifle  40  including the connecting extension  42 , wherein the method comprises the following steps: 
     (A) displacing the stopper element  22  for allowing a movement of the lever element  21  when the stopper element  22  is operated by the user such as by pushing the stopper element  22  at the proximal end  2211  thereof; 
     (B) driving the engaging end portion  2311  of the locking pin  23  to move out of the receiving chamber  101  of the stock body  10  when the lever element  21  is pressed by the user; and 
     (C) disengaging the locking pin  23  with the connecting extension  42  of the rifle for allowing the connecting extension  42  of the rifle  40  to be slid out of the receiving chamber  101  of the stock body  10 . 
     According to this preferred embodiment, during the assembling and disassembling of the rifle  40  with the replacement buttstock  100  of the present invention, the user only has to conveniently operate on the locking lever assembly  20  with a relatively few effort for enabling a rotating movement of the lever element  21  of the locking lever assembly  20  for displacing the locking pin  23  so as to unlock the connecting extension  42  of the rifle  40 . 
     When the stopper element  22  is pushed by the user for providing a moving space for the lever element  21  by receiving at least a portion of the stopper element  22  in the accommodation groove  125  of the stock body  10 , the press operation on the proximal end portion of the lever element  21  of the locking lever assembly  20  will enable a rotating movement of the lever element  21  for driving the engaging end portion  2311  of the locking pin  23  at the distal end portion  2102  of the lever element  21  to move into or get out from the receiving chamber  101  of the stock body  10  so as to slid in or slide out the connecting extension  42  of the rifle  40  for assembling or disassembling the replacement buttstock  100  with the rifle  40 . 
     Referring to  FIGS. 11A to 11D  of the drawings, this first preferred embodiment of the present invention further provides a method for adjusting an assembling position of the connecting extension  42  of the rifle  42  in the receiving chamber  101  of the stock body  10  of the replacement buttstock  100 , wherein the method comprises the following steps: 
     (α) disengaging the locking pin  23  with a first retaining groove  4222  of the connecting extension  42  of the rifle  40  which is received in the receiving chamber  101  of the stock body  10  in a first assembling position when the lever element  21  is operated to displace the locking pin  23 ; 
     (β) stopping a further movement of the lever element  21  by the stopper element  22  which is driven by the lever element  21  to be moved at a position biasing against a bottom stopping surface  124  of the stock body  10  for preventing the locking pin  23  to be moved out of the receiving chamber  101  of the stock body; and 
     (γ) engaging the locking pin  23  with a second retaining groove  4222  of the connecting extension  42  of the rifle  40  by restoring the lever element  21  to reposition the locking pin  23  after the connecting extension  42  of the rifle  40  is slid in the receiving chamber  101  of the stock body to a second assembling position which aligns the locking pin  23  with the second retaining groove  4222  of the connecting extension  42  of the rifle  40 . 
     Therefore, the locking lever assembly  20  of this preferred embodiment of the present invention can be operated for disengaging the locking pin  23  with the connecting extension  42  so as to adjust the assembling position of the connecting extension  42  in the stock body  10  for fitting the users by adjusting a distance between the rifle  40  and a shoulder of the user, enabling the user to find a comfortable holding gesture of the rifle  40  for shooting. 
     Referring to  FIGS. 13 to 19C  of the drawings, a replacement buttstock  100 ′ for detachably coupling with a rifle  40  comprises a rifle body  41  and a connecting extension  42  connected to the rifle body  41  according to a second preferred embodiment of the present invention is illustrated. The replacement buttstock  100 ′ of this preferred embodiment, which has a similar structure of the detachable buttstock  100  of the above first preferred embodiment, comprises a stock body  10 , a locking lever assembly  20 ′ coupled to the stock body  10 , and a stock pad  30  connected to the stock body  10 . 
     In this preferred embodiment, similarly, the locking lever assembly  20 ′ comprises a lever element  21 , a stopper element  22 ′, a locking pin  23 , and a restoring element  24 ′ which is embodied as a torsion spring which comprises a plurality of spring coils  241 ′, a first biasing leg  242 ′ and a second biasing leg  243 ′ extended from two ends of the plurality of spring coils  241 ′ respectively for restoring the lever element  21  when the lever element  21  is released by the user. 
     The stopper element  22 ′ of this preferred embodiment comprises a stopper body  221 ′, a reposition member  222 ′ which is embodied as a resilient spring, and an actuator member  223 ′ transversely extended from the stopper body  221 ′. The stopper body  221 ′ has a proximal end  2211 ′ which has a relative large height and a distal reduced portion  2212 ′ with a relative small height so as to allow the proximal end portion  2101  of the lever element  21  to move upward for driving the locking pin  23  to displace. The stopper body  221 ′ can be embodied to have a bottom guiding surface  2213 ′ which can be an inclined surface, an arc surface or a step-like surface, so that the proximal end portion  2101  of the lever element  21  can slide along the bottom guiding surface  2213 ′ and bias against the distal reduced portion  2212 ′, so as to move with a displacement that is enough to drive the engaging end portion  2311  of the pin body  231  of the locking pin  23  to move out of the sliding chamber  1012  of the stock body  10 . 
     In this preferred embodiment, after the stopper body  221  is pulled by holding on the actuator member  223 ′ to a position which is aligned with the accommodation groove  125 , the pressing operation on the proximal end portion  2101  of the lever element  21  at the bottom side thereof will drive the stopper body  221 ′ to move upwardly. In other words, when the stopper body  221 ′ is driven to move by pulling the actuator member  223 ′ using a finger of a hand of the user, a pin body  231  of the locking pin  23  of the locking lever assembly  20  is moved out from a sliding groove  4221  of the connecting extension  42  of the rifle  40  and also is moved out from a sliding chamber  1012  of the stock body  10 , that is to say, the engaging end portion  2311  of the pin body  231  of the locking pin  23  of the locking lever assembly  20  is no longer retained in the sliding groove  4221  of the connecting extension  42  and the sliding chamber  1012  of the stock body  10 , enabling the connecting extension  42  of the rifle  40  to be slid into or slid out of the receiving chamber  101  of the stock body  10  for installing the rifle  40  with the replacement buttstock  100 ′ or remove the replacement buttstock  100 ′ from the rifle  40 , for the pin body  231  of the locking pin  23  will no longer block the sliding movement of the engaging member  422  of the connecting extension  42  of the rifle  40 . 
     Furthermore, when the stopper element  22 ′ and the lever element  21  are released, the reposition member  222 ′ will restore the stopper element  22 ′ to its original position and the restoring element  24 ′ will restore the lever element  21  to its original position. According to this preferred embodiment of the present invention, the reposition member  222 ′ can be embodied as a resilient spring which is connected to the lever element  21 . Accordingly, when the stopper element  22 ′ is pulled at the actuator member  223 ′, the resilient spring is stretched, and when the stopper element  22 ′ is released, the resilient spring restores to its original form so as to drive the stopper body  221 ′ to move back to its original position. 
     Accordingly, the replacement buttstock  100 ′ of this preferred embodiment of the instant invention is capable of shifting between three states which are a locking state in which the lever element  21  and the stopper element  22 ′ are all at their original positions while the pin body  231  of the locking pin  23  is retained in one of the retaining grooves  4222  of the connecting extension  42  when the replacement buttstock  100 ′ is assembled with the rifle  40 , an adjusting state in which the lever element  21  is pressed to drive the stopper element  22 ′ move to a position biasing against the bottom stopping surface  124  while the engaging end portion  2311  of the pin body  231  of the locking pin  23  is moved out from the corresponding retaining groove  4222  and is still retained in the sliding groove  4221  so that simply by sliding the connecting extension  42  in the receiving chamber  101  of the stock body  10  is able to align a new retaining groove  4222  with the pin body  231  of the locking pin  23  so that the assembling position of the connecting extension  42  in the stock body  10  is adjusted, and an unlocking state in which the actuator member  223 ′ of the stopper element  22 ′ is longitudinally pulled to drive stopper body  221 ′ of the stopper element  21 ′ to longitudinally move to align the distal reduced portion  2212 ′ with the proximal end portion  2101  of the lever element  21  and the lever element  21  is transversely pressed on the proximal end portion  2101  at a bottom side thereof to bias against the distal reduced portion  2212 ′ of the stopper element  22 ′ while the lever element  21  is also rotated to drive the pin body  231  of the locking pin  23  to be moved away from the sliding groove  4221  of the connecting extension  42  and the sliding chamber  1012  of the stock body  10  so that the locking lever assembly  20 ′ is unlocked so that the connecting extension  42  of the rifle  40  can be convenient to be inserted into the receiving chamber  101  of the stock body  10  or be removed from the receiving chamber  101  of the stock body  10  for assembling or disassembling the rifle  40  with the replacement buttstock  100 ′ respectively. 
     By pulling the stopper element  22 ′, the proximal end portion  2101  of the lever element  21  is able to move with a larger distance in the unlocked state than in the adjusting state, so that the pin body  231  of the pin  23  can be moved out of the sliding groove  4221  of the connecting extension  42  and the sliding chamber  1012  of the stock body  10 . 
     According to this embodiment, the stopper element  22 ′ is mounted to the lever element  21 , while as is shown in  FIGS. 20 to 24C  of the drawings, according to an alternative mode of the second preferred embodiment, a stopper element  22 ′ may be mounted to the stock body  10  by the reposition member  222 ″ so that when the stopper element  22 ′ is longitudinally moved by pushing or pulling, the stopper element  22 ′ will not block the movement of the lever element  21  so that the lever element  21  is able to be moved to the unlocked state. In the locked state, a gap  224 ′ is formed between the proximal end portion  2101  of the lever element  21  and the stopper element  22 ′, so that when the proximal end portion  2101  of the lever element  21  is moved to the adjusting state, a bottom stopping surface  124 ′ which is formed on the stopper element  22 ″ will block the further movement of lever element  21 . While in the unlocked state, the proximal end portion  2101  of the lever element  21  is upwardly moved beyond the bottom stopping surface  124 ′. 
     Accordingly, referring to  FIGS. 19A to 19C  of the drawings, this preferred embodiment of the present invention provides a method for assembling the replacement buttstock  100  with the rifle  40  including the connecting extension  42 , wherein the method comprises the following steps: 
     (a) displacing the stopper element  22 ′ for allowing a movement of the lever element  21  when the stopper element  22 ′ is operated by the user such as by pulling the actuator member  223 ′ of the stopper element  22 ′; 
     (b) driving the engaging end portion  2311  of the locking pin  23  to move out of the receiving chamber  101  of the stock body  10  by the lever element  21  when the lever element  21  is pressed by the user; 
     (c) receiving the connecting extension  42  of the rifle  40  in the receiving chamber  101  of the stock body  10 ; and 
     (d) restoring the stopper element  22 ′ and the lever element  21  to insert the engaging end portion  2311  of the locking pin  23  into the receiving chamber  101  of the stock body  10  and retaining the connecting extension  42  of the rifle  40  in the receiving chamber  101  of the stock body  10  by the locking pin  23  when the locking lever assembly  20  is released by the user. 
     Accordingly, this second preferred embodiment of the present invention provides a method for disassembling the replacement buttstock  100  with the rifle  40  including the connecting extension  42 , wherein the method comprises the following steps: 
     (A) displacing the stopper element  22 ′ for allowing a movement of the lever element  21  when the stopper element  22 ′ is operated by the user such as by pulling the actuator member  223 ′ of the stopper element  22 ′; 
     (B) driving the engaging end portion  2311  of the locking pin  23  to move out of the receiving chamber  101  of the stock body  10  when the lever element  21  is pressed by the user; and 
     (C) disengaging the locking pin  23  with the connecting extension  42  of the rifle for allowing the connecting extension  42  of the rifle  40  to be slid out of the receiving chamber  101  of the stock body  10 . 
     When the stopper element  22 ′ is pulled by the user for providing a moving space for the lever element  21  by aligning the distal reduced portion  2212 ′ with a relatively small height with the proximal end portion of the lever element  21  or just moving away the stopper element  22 ′ so that the stopper element  22 ′ is not above the lever element  21  to stop the movement of the lever element  21 , the press operation on the proximal end portion of the lever element  21  of the locking lever assembly  20  will enable a rotating movement of the lever element  21  for driving the engaging end portion  2311  of the locking pin  23  at the distal end portion  2102  of the lever element  21  to move into or get out from the receiving chamber  101  of the stock body  10  so as to slid in or slide out the connecting extension  42  of the rifle  40  for assembling or disassembling the replacement buttstock  100  with the rifle  40 . 
     Referring to  FIG. 18A to 18B  of the drawings, the second embodiment of the present invention further provides a method for adjusting an assembling position of the connecting extension  42  of the rifle  42  in the receiving chamber  101  of the stock body  10  of the replacement buttstock  100 , wherein the method comprises the following steps: 
     (α) disengaging the locking pin  23  with a first retaining groove  4222  of the connecting extension  42  of the rifle  40  which is received in the receiving chamber  101  of the stock body  10  in a first assembling position when the lever element  21  is operated to displace the locking pin  23 ; 
     (β) stopping a further movement of the lever element  21  by the stopper element  22 ′ which is driven by the lever element  21  to be moved at a position biasing against a bottom stopping surface  124  of the stock body  10  or a bottom stopping surface  124 ′ of the stopper element  22 ′ for preventing the locking pin  23  to be moved out of the receiving chamber  101  of the stock body; and 
     (γ) engaging the locking pin  23  with a second retaining groove  4222  of the connecting extension  42  of the rifle  40  by restoring the lever element  21  to reposition the locking pin  23  after the connecting extension  42  of the rifle  40  is slid in the receiving chamber  101  of the stock body to a second assembling position which aligns the locking pin  23  with the second retaining groove  4222  of the connecting extension  42  of the rifle  40 . 
     One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting. 
     It will thus be seen that the objects of the present invention have been fully and effectively accomplished. The embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and are subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.