Abstract:
A rail extension device for a belt fed machine gun includes a first and a second section of rail for mounting auxiliary devices, the second section being rotatable relative to the first section to prevent a collision between an auxiliary device mounted on the second section of rail and the weapon when a feed tray cover is opened to reload.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of and claims priority to copending U.S. patent application Ser. No. 13/528,806 filed Jan. 18, 2012, the entire disclosure of which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to rail interface systems, and, more particularly, to a rail extension device for a firearm. 
       BACKGROUND 
       [0003]    The need to effectively see a target and aim a weapon in the direction of the target is well-recognized. Auxiliary devices to facilitate illuminating a target or aiming a weapon are known. Examples of known auxiliary devices include scopes, visible and infrared illuminators, laser pointers, combined illuminator/laser pointer devices, night vision devices and/or infrared imagers. Auxiliary devices may be mounted onto a rail(s) of a firearm to provide increased flexibility or broader functionality. The rail(s) may be generally parallel with a weapon barrel and may be positioned above, below, or to the side of the barrel to provide one or more locations for the mounting of accessory devices. Auxiliary devices are often mounted to weapons having a rail with a certain profile, for example a rail profile consistent with the MIL-STD-1913. 
         [0004]    Some auxiliary devices may be paired with another auxiliary device, wherein the combination provides an enhanced use. For example, a night vision scope may be paired with and used in conjunction with an optical scope. In another example, an optical scope may be paired with a secondary power multiplier or extender. When a user pairs auxiliary devices, they may have one device mounted at a rear portion of the firearm and the additional device mounted at a forward portion of the firearm.  FIG. 1  is an isometric view of a firearm, shown as a machinegun. According to one embodiment, the firearm  100  may be an M240 machine gun having a mounting rail  120 , e.g. a RIS system, having a MIL-STD-1913 Picatinny profile. In the illustrated embodiment, a daytime scope  118  may be mounted to a rear portion of the mounting rail  120 . In certain conditions, the daytime scope  118  may be unusable due to weather conditions, such as lack of sunlight. If a user decides to exchange the daytime scope  118  with a night vision capable scope, for example, each scope may need to be individually adjusted when remounted to the firearm  100 . Changing devices may be difficult and time consuming. Each time an auxiliary device is exchanged, the firearm  100  may require sight adjustment, which may become cumbersome and waste valuable time, especially in military or force protection situations. A user may wish to mount an additional scope, e.g. a night vision scope  222  (shown in  FIG. 2 ) to an extended rail section of the mounting rail  120  in front of the daytime scope  118 , i.e. a position closer to the barrel  102 , in order to add nighttime operation and capability to the daytime scope  118  without the need to replace the daytime scope  118 . It is to be understood that systems consistent with the present disclosure may be used in connection with a variety of auxiliary device configurations, and is not limited to the combination of night vision and daytime auxiliary devices. 
         [0005]    The firearm  100  may include a barrel  102 , a buttstock  104 , a folding bipod stand  106  configured to support the firearm  100 , a receiver assembly  108 , a trigger housing assembly  110 , a feed tray  112  and a feed tray cover  114  in a closed position. The barrel  102  defines the forward portion of the firearm  100  and the buttstock  104  defines the rearward portion of the firearm  100 . The longitudinal axis A of the firearm  100  may extend generally parallel with the barrel  102 . The receiver assembly  108  may serve as a support for all major components and may house the action of the firearm  100 , and through a series of cam ways, may control functioning of the firearm  100 . The feed fray  112  may serve as a guide for positioning a linked ammunition belt to assist in chambering of the ammunition. The feed tray cover  114  may serve as an upper portion of the feed tray  112  and may be configured to feed linked ammunition belts and hold ammunition cartridges in position for stripping, feeding, and/or chambering. The mounting rail  120  may be formed as an integral part of the feed tray cover  114  and may be generally parallel with the longitudinal axis A of the firearm  100  and the barrel  102 . The firearm  100  may further include a carrying handle  116  attached to the barrel  102 , wherein the carrying handle may be configured to assist in handling and/or changing the barrel  102 . 
         [0006]      FIG. 2  is a side view of a portion of the firearm of  FIG. 1  with the feed tray cover  114  rotated to an open position. Mounted to the mounting rail  120  maybe the daytime scope  118 . For purposes of illustration, an auxiliary device, for example a night vision scope  222  is positioned in front of the daytime scope  118 . The feed tray cover  114  may be rotatably coupled to a portion of the receiver assembly  108  and may be configured to move between an open and closed position as indicated by the double arrow  226 . When the firearm  100  is equipped with an additional auxiliary device, such as the night vision scope  222 , the feed tray cover  114  may not be able to fully rotate to an open position due to the the scope striking a portion of the weapon. In the illustrated embodiment, rotation of the feed tray cover  114  to the open position may be prevented due to the night vision scope  222  making physical impact (indicated by the arrow  228 ) with a portion of the receiver assembly  108 . In this instance, the user may be required to remove the night vision scope  222  in order for the feed tray cover  114  to fully roatate to the open position, resulting in wasting valuable time during combat situations. 
         [0007]      FIG. 3  is a front view of the firearm of  FIG. 1  having the night vision scope  222  attached to the mounting rail  120  with the handle  116  and barrel  102  alternating between a first position and a second position during a barrel removal. In the illustrated embodiment, the quick-detachable barrel  102  may be configured to be removed rapidly via a barrel release button (not shown) and rotation of the carrying handle  116 . When the carrying handle  116  is in a first position, shown in  FIG. 1 , the barrel  102  is securely fixed to the receiver assembly  108  of the firearm  100 . The carrying handle  116  is configured to move from the first position, generally parallel a side surface of the receiver assembly  108  of the firearm  108 , to a second position, generally parallel to a top surface of the receiver assembly  108 . When the carrying handle  116  is in the second position, the barrel  102  may be removed from the firearm  102 . In the illustrated embodiment, the carrying handle  116  may be configured to move from first and second positions as indicated by the double arrow  330  and barrel  102  may be configured to move from first and second positions as indicated by the double arrow  332 . 
         [0008]    When the firearm  100  is equipped with an additional auxiliary device, such as the night vision scope  222 , the carrying handle  116  may not be able to fully rotate to the second position thus preventing removal of the barrel  102 . Rotation of the carrying handle  116  to the second position may be prevented due to the night vision scope  222  making physical impact (indicated by the arrow  334 ) with a portion of the carrying handle  116 . In this instance, the user would be required to remove the night vision scope  222  in order for the carrying handle  116  to fully rotate to the second position to remove the barrel  102 . 
         [0009]    In addition to the problems described above, users may have difficulty with the current method of opening the feed tray cover of a M240 machinegun. Opening of the feed tray cover may be particularly difficult when an auxiliary device and/or sight is coupled near the rear position of the firearm, which may require a user to use both hands. For example, in the illustrated embodiment of  FIG. 2 , feed tray cover  114  may include locking latches  224  located on either side of the feed tray cover  114 . The locking latches  224  are configured to secure the feed tray cover  114  to the feed tray  112  when the feed tray cover  114  is in a closed position. When a user needs to open the feed tray cover  114 , the user applies an inward force to both the locking latches  224  in order to release the feed tray cover  114  from the feed tray  112 . A user may then lift the feed tray cover  114  into an open position. Due to the position of the locking latches  224  on either side of the feed tray cover  114 , it may be difficult for a user to apply the necessary inward force to both latches  224  with one hand, particularly when a scope or other auxiliary device is coupled near the rear position of the firearm. Instead, a user may need to use both hands to apply proper force, which may be cumbersome and time-consuming. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Features and advantages of the claimed subject matter will be apparent from the following detailed description of embodiments consistent therewith, which description should be considered with reference to the accompanying drawings, wherein: 
           [0011]      FIG. 1  is an isometric view of a firearm having a standard rail interface system and rear scope attached thereto with a feed tray cover of the firearm in a closed position; 
           [0012]      FIG. 2  is a side view of a portion of the firearm and the rail interface system and scope of  FIG. 1  having a front scope attached thereto with the feed tray cover in an opened position; 
           [0013]      FIG. 3  is a front (distal or muzzle facing) view of the firearm of  FIG. 1  having a standard rail interface system and front and rear scopes attached thereto with a handle and barrel of the firearm alternating between a first position and a second position during a barrel exchange; 
           [0014]      FIG. 4A  is an isometric view of one embodiment of a rail extension device mounted on the standard rail interface system of the firearm of  FIG. 1  with the feed tray cover in the closed position, consistent with the present disclosure; 
           [0015]      FIG. 4B  is an alternate isometric view showing a feed tray cover release assembly of the rail extension device of  FIG. 4A ; 
           [0016]      FIG. 5  is an enlarged view of a portion of the rail extension device of  FIG. 4B ; 
           [0017]      FIG. 6  is an isometric view of the rail extension device of  FIG. 4A  with the feed tray cover in the opened position; 
           [0018]      FIG. 7A  is an isometric view of the rail extension device of  FIG. 4A  with the rail member in a first rail member position; 
           [0019]      FIG. 7B  is an isometric view of the rail extension device of  FIG. 4A  with the rail member in a second rail member position; 
           [0020]      FIG. 7C  is an exploded view of the rail extension device of  FIG. 4A  with the rail member in the second rail member position; 
           [0021]      FIG. 8  is an isometric view of the rail extension device of  FIG. 7A  mounted to the standard rail interface system of the firearm of  FIG. 1  showing front and rear scopes attached to the rail extension device with the feed tray cover in the opened position and the rail member in the second rail member position; 
           [0022]      FIG. 9  is a front (distal or muzzle facing) view of the rail extension device of  FIG. 7A  mounted to the standard rail interface system of the firearm of  FIG. 1  showing front and rear scopes attached to the rail extension device with the handle and barrel of the firearm alternating between a first position and a second position during a barrel exchange; 
           [0023]      FIG. 10  is an isometric view of one embodiment of another rail extension device mounted on the standard rail interface system of the firearm of  FIG. 1  with the feed tray cover in the closed position, consistent with the present disclosure; 
           [0024]      FIG. 11  is an alternate isometric view showing a feed tray cover release assembly of the rail extension device of  FIG. 10 ; 
           [0025]      FIG. 12  is an isometric view of the rail extension device of  FIG. 10  mounted on the standard rail interface system of the firearm of  FIG. 1  with the feed tray cover in the open position 
           [0026]      FIG. 13  is an isometric view of the rail extension device of  FIG. 10  with the rail member in a first rail member position; 
           [0027]      FIG. 14  is an isometric view of the rail extension device of  FIG. 10  with the rail member in a second rail member position; 
           [0028]      FIG. 15  is an exploded view of the rail extension device of  FIG. 10  with the rail member in the second rail member position; 
           [0029]      FIG. 16  is a section view taken through line  1 - 1  in  FIG. 10 ; and 
           [0030]      FIG. 17  is an end view of the rail extension device of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    In general, a rail extension device consistent with the present disclosure may be configured to be coupled to a firearm. The rail extension device may include a base plate having a top surface defining a first rail interface, the base plate having a first end configured to be rotatably coupled to a frame portion of the firearm and a second end configured to be coupled to a feed tray cover of the firearm. The base plate may be movable about a first axis between a first base plate position and a second base plate position, wherein the first axis may be substantially orthogonal with a barrel of the firearm. The rail extension device may further include a rail member having a top surface defining a second rail interface, wherein the rail member may be rotatably coupled to the base plate and movable about a second axis between a first rail member position and a second rail member position. The second axis may be substantially parallel with the barrel of the firearm when the base plate is in the first base plate position. When the rail member and base plate are in the first rail member position and the first base plate positions, respectively, the top surface of the base plate and the top surface of the rail member may form a substantially planar rail interface. When the rail member is in the second rail member position, the top surface of the rail member may be substantially orthogonal to the top surface of the base plate. The rail extension device may further include a release assembly configured to apply pressure to locking latches of a feed tray cover of the firearm. The release assembly may be configured to allow the feed tray cover to be opened with one hand. 
         [0032]    A device consistent with the present disclosure may allow a user to fully open the feed tray cover while having paired auxiliary devices mounted on the firearm, eliminating the need to remove either of the devices, allowing the devices to remain aligned and calibrated. Further, a device consistent with the present disclosure may allow a quick and easy one-handed method of opening the feed tray cover, particularly when an auxiliary device and/or a sight is coupled near the rear position of the firearm. 
         [0033]    The rail extension device  400  of the present disclosure is intended for use with any known type of weapon and/or firearm. For purpose of illustration throughout the entirety of the present disclosure, a typical military combat firearm  100 , e.g. an M240 machine gun, is depicted.  FIGS. 4A-4B  are isometric views of one embodiment of a rail extension device mounted on the firearm of  FIG. 1  with the feed tray cover  114  in the closed position, consistent with the present disclosure. In the illustrated embodiment, the rail extension device  400  is mounted to the typical mounting rail  120  of the firearm  100 . 
         [0034]    In the embodiments described herein, the rail extension device  400  includes a base plate  402  having a first base plate end  404 A configured to be rotatably coupled to a portion of the receiver assembly  108 . The base plate  402  has a second base plate end  404 B configured to be coupled to the feed tray cover  114  via a fastener, such as a screw  768  (shown in  FIG. 7C ), sized and/or shaped to pass through an aperture  770  (shown in  FIG. 7C ) defined on the second base plate end  404 B. In the illustrated embodiment, the first base pate end  404 A is in a position near the front (barrel  102 ) of the firearm  100  and the second base plate end  404 B is in a position closer to the rear (buttstock  104 ) of the firearm  100 . The base plate  402  may further include a top surface  406 , generally parallel to the axis A in a horizontal plane when in a first base plate position, wherein the top surface  406  may define an interface to which various auxiliary devices can be mounted. The rail extension device  400  further includes a rail member  408  rotatably coupled to the base plate  402 , wherein the rail member  408  includes a first rail member end  409 A and a second rail member end  409 B. In the illustrated embodiment, the first rail member end  409 A is positioned near the front of the firearm  100  and the second rail member end  409 B is in a position closer to the rear of the firearm  100 . Similar to the base plate  402 , the rail member  408  includes a top surface  410 , generally parallel to the axis A when in the first rail member position and the base plate  402  in the first base plate position, wherein the top surface  410  may define an interface to which auxiliary devices can be mounted. The rail extension device  400  may further include a feed tray cover release assembly  412  described in greater detail below. In the illustrated embodiment, the top surfaces  406 ,  410  of the base plate  402  and rail member  408 , respectively, may have a MIL-STD-1913 Picatinny standard rail profile. For example, the top surfaces  406 ,  410  may define a series of ridges with a T-shaped cross-section interspersed with flat “spacing slots”. Auxiliary devices can be mounted to the base plate  402  and rail member  408  by a variety of means known to one skilled in the art. 
         [0035]      FIG. 5  is an enlarged view of the feed tray cover release assembly  412  of the rail extension device  400  of  FIGS. 4A-4B . In the illustrated embodiment, the feed tray cover release assembly  412  includes a rail mount body  514  configured to engage the mounting rail  120  defined on the firearm  100 . The feed tray cover release assembly  412  may also include a first rigid member  516 A coupled to a first portion of the rail mount body  514  and a second rigid member  516 B coupled to a second portion of the rail mount body  514 , wherein the first and second portions oppose one another. For example, in the illustrated embodiment, the first rigid member  516 A may be coupled to a left side (based on a proximal or user view) of the rail mount body  514  and the second rigid member  516 B may be coupled to a right side, such that the first and second rigid members  516 A,  516 B oppose one another. The first and second rigid members  516 A,  516 B may define first and second contact portions  518 A,  518 B, respectively, configured to make contact and engage locking latches  224  located on corresponding sides of the feed tray cover  114 . 
         [0036]    The feed tray cover release assembly  412  further includes a release lever  520  coupled to a shaft  515  extending from the rail mount body  514 . The shaft  515  may provide an axis  522 , generally perpendicular to axis A on the horizontal plane, about which the release lever  520  may rotate from a first release lever position (shown in the  FIG. 5 ) to a second release lever position (rotation of approximately 90 degrees). The first rigid member  516 A defines a cammed surface  517  configured to provide a prescribed motion to a roller member  786  (shown in  FIG. 7C ) coupled to the release lever  520 . In the illustrated embodiment, the release lever  520  is coupled to the left side of the rail mount body  514  and configured to engage the cammed surface  517  of the first rigid member  516 A via the roller member  786  (shown  FIG. 7C ). In another embodiment, the release lever  520  may be coupled to a shaft (not shown) extending from the right side of the rail mount body  514 , wherein the release lever  520  may be configured to engage a cammed surface (not shown) of the second rigid member  516 B. 
         [0037]    The release lever  520  may be configured to apply a force to the cammed surface  517  of the first rigid member  516 A via the roller member  786  (shown  FIG. 7C ) when the release lever  520  rotates to the second release lever position, such that the first and/or second contact portions  518 A,  518 B move in an inward direction towards the rail mount body  514  (a direction generally perpendicular to axis A on the horizontal plane), thereby forcing the respective locking latches  224  inward and allowing the feed tray cover  114  to be opened by the user. The first and second rigid members  516 A,  516 B may be horizontally spaced (e.g. generally perpendicular to the axis A on the horizontal plane) by a distance slightly greater than a width of the feed tray cover  114 , including the locking latches  224 , such that when the release lever  520  is in the first release lever position, the first and second contact portions  518 A,  518 B may make contact with, but do not force the respective locking latches  224  inward, thereby allowing the feed tray cover to remain in a closed position. The operation of the feed tray cover release assembly  412  will be described in greater detail below. 
         [0038]    It should be noted that the feed tray cover release assembly  414  may be coupled to the existing mounting rail  120  of the firearm  100  and fully operable without the addition of the rail extension device  400  to the firearm  100 . 
         [0039]      FIG. 6  is an isometric view of the rail extension device of  FIG. 4A  with the feed tray cover in the opened position. As described above, upon application of appropriate amount of force against the locking latches  224 , the user may open the feed tray cover  114 . In the illustrated embodiment, the rail extension device  400  may be coupled to the feed tray cover  114 , such that, the base plate  402  of the rail extension device  400  may move about an axis  732  (shown in  FIGS. 7A-7B ) between a first base plate position and a second base plate position in conjunction with the rotation of feed tray cover  114  between the closed and open positions as indicated by the double arrow  226 . The first base plate position may correspond to the closed position of the feed tray cover  114  and the second base plate position may correspond to the open position of the feed tray cover  114 . In other words, when the feed tray cover  114  is in the closed position (shown in  FIG. 4A ) the base plate  402  is in the first base plate position and when the feed tray cover  114  is in the open position (shown in  FIG. 6 ) the base plate  402  is in the second base plate position. 
         [0040]    The rail member  408  of the rail extension device  400  may be configured to move about an axis  736  (shown in  FIGS. 7A-7B ) between a first rail member position (shown in  FIG. 7A ) and a second rail member position (as shown in  FIGS. 6 and 7B ) as indicated by the double arrow  624 . When in the second rail member position, the top surface  410  of the rail member  408  may be substantially perpendicular to the top surface  406  of the base plate  402 . When in the first rail position (shown in  FIG. 7A ), the top surface  410  of the rail member  408  and the top surface  406  of the base plate  402  may form a substantially planar interface. 
         [0041]      FIG. 7A  is an isometric view of the rail extension device of  FIG. 4A  with the rail member in the first rail member position. As described above, the first and second contact portions  518 A,  518 B of the first and second rigid members  516 A,  516 B, respectively, may be configured to move in an inward direction towards the rail mount body  514  thereby forcing respective locking latches  224  (shown in  FIGS. 2 ,  4 B, and  5 ) in an inward direction. In the illustrated embodiment, the first contact portion  518 A (shown in  FIG. 5 ) may be moved about a vertical axis  742 A and the second contact portion  518 B may move about a vertical axis  742 B, wherein the axes  742 A,  742 B are generally perpendicular to axis A on a vertical plane when the base plate  402  is in the first base plate position. 
         [0042]    The first base plate end  404 A includes at least one support member  734  extending therefrom. The at least one support member  734  defines an aperture through which a wrist pin  730  may pass and extend therefrom generally perpendicular to axis A on the horizontal plane. The wrist pin  730  may provide the axis  732  on which the base plate  402 , as well as feed tray cover  114 , rotates. The wrist pin  730  may be configured to retain at least the first base plate end  404 A to the receiver assembly  108  of the firearm  100 . The wrist pin  730  may further include a latch member  794  (shown in  FIG. 7C ) configured to secure the wrist pin  730  to the support member  734 . In the illustrated embodiment, the first base plate end  404 A includes first and second support members  734  extending therefrom (shown in  FIGS. 7B-7C ), wherein the wrist pin  730  extends between and is supported by at least both the first and second mounting members  734 . 
         [0043]    The first rail member end  409 A includes at least one support member  740  extending therefrom. The at least one support member  740  defines an aperture through which a fastener, such as a pin  804  (shown in  FIG. 7C ) may pass and extend therefrom generally perpendicular to axis A on the horizontal plane when the rail member  408  is in the first rail member position. In the illustrated embodiment, the first rail member end  409 A includes first and second support members  740  extending therefrom (shown in  FIG. 7C ), wherein the pin  804  (shown in  FIG. 7C ) extends between and is supported by at least both the first and second mounting members  740 . A fastener, such as an e-clip  806  (shown in  FIG. 7C ) may be configured to secure and retain the pin  804  to the support members  740 . 
         [0044]    The rail extension device  400  further includes a release trigger  726  rotatably coupled to the first and second support members  740  of the rail member  408  via the pin  804 . The release trigger  726  may be configured to move about an axis  738 , generally perpendicular to axis A on the horizontal plane, between a first release trigger position and a second release trigger position. The pin  804  may provide the axis  738  on which the release trigger  726  rotates. The release trigger  726  may define a contact portion  728  configured to make contact with at least a portion of the receiver assembly  108  when the feed tray cover  114  and base plate  402  are rotated in directions toward the open position. When the release trigger  726  is moved to the second release trigger position, the rail member  408  moves about the axis  736 , generally parallel with axis A, from the first rail member position to the second rail member position, the process of which is described in greater detail below. 
         [0045]      FIG. 7B  is an isometric view of the rail extension device of  FIG. 4A  with the rail member in the second rail member position. In the illustrated embodiment, the release trigger  726  may be coupled to at least one hook  744 . The at least one hook  744  is configured to matingly engage at least one catch  746  coupled to the base plate  402  when the rail member  408  is in the first rail member position. The at least one catch  746  is configured to retain the rail member  408  in the first rail member position. In the illustrated embodiment, the release trigger  726  is coupled to first and second hooks  744  via a shaft  808  (shown in  FIG. 7C ), wherein the shaft  808  may be positioned within a channel  810  (shown in  FIG. 7C ) configured to receive the shaft  810  and first and second hooks  744 . The first and second hooks  744  may each define apertures through which the shaft  810  may pass. The first and second hooks  744  may be extending from a bottom surface of the rail member  408 , wherein the bottom surface may be sized and shaped to correspond to and cooperate with a portion of the base plate  402  when the rail member  408  is in the first rail member position. 
         [0046]    The release trigger  726  may be configured to apply a force to the first and second hooks  744  when in the second release trigger position, such that the first and second hooks  744  disengage from the first and second catches  746 . When the release trigger  726  is in the second release trigger position, the first and second hooks  744  disengage from the first and second catches  746 , thereby allowing the rail member  408  to rotate about axis  736  from the first rail member position to the second rail member position. In the illustrated embodiment, when the first and second hooks  744  disengage from the first and second catches  746 , the rail member  408  is configured to rotate in a direction towards the left side (from a proximal or user facing view) of the rail extension device  400 , generally in a direction away from the carrying handle  116 . It should be noted that in another embodiment, rotation of the rail member  408  from the first rail member position to the second rail member position may be reversed, wherein the rail member  408  may rotate to the right side (from a proximal or user facing view) of the rail extension device  400  (assuming the carrying handle  116  position is also reversed, such that the carrying handle is on the left side of the firearm  100 ). 
         [0047]    The rail extension device  400  further includes a bracket  748  having a first end coupled to a lever member  764  (shown in  FIG. 7C ) of a spring assembly  754  and a second end coupled to the rail member  408 . The spring assembly  754  includes a torsion spring  756  coupled to an arbor member  758 . The spring assembly  754  described in greater detail below. The rail extension device  400  further includes a first link  750  and a second link  752 , wherein the first and second links  750 ,  752  have first and second ends. The first end of the first link  750  is coupled to the base plate  402  and the first end of the second link  752  is coupled to the rail member  408 . The second end of the first link  750  is coupled to the second end of the second link  752 . The first and second links  750 ,  752  are configured to retain the rail member  408  when in a second rail member position, thereby preventing the rail member  408  from over-rotating past the second rail member position. 
         [0048]      FIG. 7C  is an exploded view of the rail extension device of  FIG. 4A  with the rail member in the second rail member position. In the illustrated embodiment, the first end of the bracket  748  is rotatably coupled to the rail member  408  via a fastener, such as a spring pin  802 , configured to retain the first end of the bracket  748  and provide an axis, generally parallel with axis A, about which the bracket  748  may rotate. The second end of the bracket  748  is coupled to the lever member  764  of the spring assembly  754  via a protrusion formed on the second end of the bracket  748 . The protrusion is sized and/or shaped to matingly engage a first aperture defined on a portion of the lever member  764 , wherein the protrusion forms an axis, generally parallel with axis A, about which the bracket  748  may rotate. The lever member  764  further defines a second aperture through which a fastener  766  passes and fixes the lever member  764  to the arbor member  758 . 
         [0049]    In the illustrated embodiment, the torsion spring  756  has a first torsion spring end  757 A and a second torsion spring end  757 B. The first torsion spring end  757 A is coupled to the arbor member  758  and the second torsion spring end  757 B is coupled to a torsion adjuster member  760 . The base plate  402  includes a channel  762  generally extending along a longitudinal length of the base plate  402  in a direction generally parallel to axis A. The channel  762  is configured to house at least a portion of the torsion spring  756 . The arbor member  758  and torsion adjuster member  760  may be configured to retain the torsion spring  756  within the channel  762 . The torsion spring  756  may include a flexible metal wire or a high-strength elastic material and have a general helical shape, wherein the torsion spring  756  may provide an axis B, generally parallel to axis A, about which first and second torsion spring ends  757 A,  757 B may rotate. The torsion spring  756  may be configured to store a mechanical energy when the first and second torsion spring ends  757 A,  757 B are rotated about axis B in opposite directions. Those skilled in the art will recognize that the torsion spring  756  may be configured to store a mechanical energy when the first torsion spring end  757 A is rotated about axis B and the second torsion spring end  757 B is fixed and/or vice versa (first torsion spring end  757 A fixed and second torsion spring  757 B is rotated). It should be noted that in other embodiments, a torsion bar may be included as opposed to a spring. 
         [0050]    In the illustrated embodiment, the torsion adjuster member  760  may be configured to secure the second torsion spring end  757 B in a fixed position and to increase and/or decrease torque of the torsion spring  756 . The arbor member  758  may be configured to rotate about axis B from a first arbor member position to a second arbor member position. As described above, the arbor member  758  is coupled to the lever member  764  via a fastener  766  and the lever member  764  is further coupled to the bracket  748  via a protrusion formed on the second end of the bracket  748  sized and/or shaped to engage the first aperture on the lever member  764 . Thus, when the rail member  408  rotates about axis  736  from the second rail member position to the first rail member position, the bracket  748  is configured to apply a force to the arbor member  758  via the lever member  764 , thereby causing the arbor member  758  to rotate about axis B. 
         [0051]    When the rail member  408  is in the second rail member position (shown in  FIG. 7C ), the arbor member is in the second arbor member position. When the user desires to engage the hooks  744  of the rail member  408  with the catches  746  of the base plate  402 , the user may move the rail member  408  from the second rail member position to the first rail member position, thereby causing the bracket  748  to apply a force to the arbor member  758 , in turn causing the arbor member  758  to move from the second arbor member position to the first arbor member position. As the arbor member  758  moves from the second arbor member position to the first arbor member position, the arbor member  758  applies a force to the first torsion spring end  757 A, thereby twisting the first torsion spring end  757 A about axis B, resulting in the increase of stored energy, or torque, in the torsion spring  756 . Similarly, the torsion spring  756  is configured to “unwind”, wherein the first torsion spring end  757 A may apply a force to the arbor member  758 , thereby causing the arbor member  758  to rotate about axis B from the first arbor member position to the second arbor member position, which in turn causes the lever member  764  to rotate and apply force to the bracket  748  and rail member  408 . 
         [0052]    The torsion spring  756  has a first amount of stored force, or torque, when the rail member  408  is in the first rail member position and the torsion spring  756  has a second amount of stored torque when the rail member  408  is in the second rail member position, wherein the first amount of stored torque is greater than the second amount of stored torque. Therefore, as generally understood by one skilled in the art, the torsion spring  756  may be fully loaded when the rail member  408  is in the first rail member position. 
         [0053]    As described above, when the rail member  408  is in the first rail member position, the first and second hooks  744  of the rail member  408  are engaged with the first and second catches  746  of the base plate  402 . When the rail member  408  is in the first rail member position, the torsion spring  756  is fully loaded and the first amount of stored torque is applied to the rail member  408 . When the contact portion  728  of the release trigger  726  makes contact with a portion of the receiver assembly  108  of the firearm  100 , the release trigger  726  rotates about axis  738  from the first release trigger position to the second release trigger position, thereby causing the first and second hooks  744  to disengage from the first and second catches  746 . When the first and second hooks  744  disengage from the first and second catches  746 , the rail member  408  moves to the second rail member position due to the application of the first amount of stored torque from the torsion spring  756 . 
         [0054]    The release trigger  726  is coupled to first and second hooks  744  via the shaft  808 , wherein the shaft  808  is sized and/or shaped to pass through apertures defined on the first and second hooks  744 . The shaft  808  may define a recess configured to receive and retain a fastener, such as an e-clip  806 . In the illustrated embodiment, the shaft  808  may define multiple recesses configured to receive and retain multiple c-clips  806 . The e-clips  806  are configured to retain a portion of the first and second hooks  744  in a secure position and/or in alignment with the first and second catches  746 . The e-clips  806  may be further configured to apply a force in a generally longitudinal direction, generally parallel to axis A, from the shaft  808  to the first and second hooks  744 , thereby moving the hooks  744  from the engaged position with the catches  746 , to a disengaged position. Double-torsion springs  820  may further be provided to create a spring bias force that urges the first and second hooks  744  in a linear direction towards the engaged position. In addition, a return spring  814  may be provided to create a spring bias force that urges the shaft  808  in a linear direction towards the release trigger  726 . 
         [0055]    When the base plate  402  moves from the first base plate position to the second base plate position, the contact portion  728  of the release trigger  726  may make contact with a portion of the receiver assembly  108  of the firearm  100 , thereby causing the release trigger  726  to move from the first release trigger position to the second release trigger position. When in the second release trigger position, the release trigger  726  is configured to apply a force to the shaft  808  in a direction towards the second rail member end  409 B and generally parallel to axis A. In turn, the shaft  808  is configured to apply a force to the first and second hooks  744  via the e-clips  806 , thereby causing the first and second hooks  744  to disengage from the first and second catches  746 . When the first and second hooks  744  disengage from the first and second catches  746 , the first amount of stored torque in the torsion spring  756  is applied to the arbor member  758 , wherein the torsion spring  758  “unwinds” thereby causing the arbor member  758 , and lever member  764 , to rotate from the first to the second arbor member position, thereby applying a force against the bracket  748 . The bracket  748  forces the rail member  408  to rotate about axis  736  from the first rail member position to the second rail member position. 
         [0056]    As described above, first and second links  750 ,  752  are provided and configured to prevent the rail member  408  from over-rotating past the second rail member position. The first end of the first link  750  is coupled to a third base plate knuckle member  818  formed on the base plate  402 , wherein the third base plate knuckle member  818  and the first end of the first link  750  define apertures through which a fastener, such as a pin  816 B, may pass. The pin  816 B is configured to retain the first end of the first link  750  to the third base plate knuckle member  818 . The pin  816  may provide an axis about which the first link  750  may rotate. The first end of the second link  752  is coupled to a third rail member knuckle member  812  formed on the rail member  408 , wherein the third rail member knuckle member  812  and the first end of the second link  752  define apertures through which the shaft  808  may pass, wherein the shaft may provide an axis about which the second link  752  may rotate. The second ends of the first and second links  750 ,  752  are coupled to one another, wherein the second ends may define apertures through which a fastener, such as a pin  816 A, may pass. Similarly, the pin  816 A may provide an axis about which the first and second links  750 ,  752  may rotate. 
         [0057]    As described above, the rail member  408  may be rotatably coupled to the base plate  402 . In the illustrated embodiment, the base plate  402  includes a first base plate knuckle member  796 A and a second base plate knuckle member  796 B. The rail member  408  includes a first set of rail member knuckle members  798 A and a second set of rail member knuckle members  798 B sized and/or shaped to correspond to and cooperate with the first and second base plate knuckle members  796 A,  796 B, respectively. The rail member  408  is coupled to the base plate  402  via the knuckle members, wherein the first set of rail member knuckle members  798 A is coupled to the first base plate knuckle member  796 A and the second set of rail member knuckle members  798 B is coupled to the second base plate knuckle member  796 B. The knuckle members  796 A,  796 B,  798 A,  798 B may define apertures through which fasteners may pass, such as spring pins  800 A,  800 B. In the illustrated embodiment, spring pin  800 A is configured to secure the first set of rail member knuckle members  798 A to retain the first base plate knuckle member  796 A and spring pin  800 B is configured to retain the second set of rail member knuckle members  798 B to the second base plate knuckle member  796 B. The spring pins  800 A,  800 B may provide the axis  736  about which the rail member  408  may rotate from the first rail member position to the second rail member position. 
         [0058]    As described above, a user may desire to open the feed tray cover  114 . The feed tray cover release assembly  412  is configured to provide a force against locking latches  224  of the feed tray cover  114 , thereby allowing the user to open the feed tray cover  114 . In the illustrated embodiment, the feed tray cover release assembly  412  may be coupled to the base plate  402  via the fastener  768 . In particular, the rail mount body  514  may define an aperture  772  sized and/or shaped to receive the fastener  768 . The rail mount body  514  may further define a bottom surface configured to be attached to the existing mounting rail  120  of the firearm  100 . As described above, the feed tray cover release assembly  412  includes first and second rigid members  516 A,  516 B coupled on either side of the rail mount body  514 . In the illustrated embodiment, the rail mount body  514  may include apertures  774  positioned on either side of the rail mount body  514 , wherein the apertures  774  are sized and/or shaped to receive fasteners, such as first fastening pins  784 A. The first and second rigid members  516 A,  516 B define a first set of apertures  780  corresponding to and aligned with apertures  774 , wherein the first set of apertures  780  are sized and/or shaped to receive the first fastening pins  784 A. The first and second rigid members  516 A,  516 B are rotatably coupled to either side of the rail mount body  514  via the first fastening pins  784 A configured to pass through apertures  774  and the first set of apertures  780  and to retain the first and second rigid members  516 A,  516 B to the rail mount body  514 . The first fastening pins  784 A may provide axes  742 A,  742 B about which the first and second rigid members  516 A,  516 B may rotate about, respectively. 
         [0059]    The feed tray cover release assembly  514  further includes a z-bar member  776  positioned between a top surface of the rail mount body  514  and a bottom surface of the base plate  402 . The z-bar member  776  may define apertures  778  on either side of the Z-bar member  776  sized and/or shaped to receive fasteners, such as second fastening pins  784 B. The first and second rigid members  516 A,  516 B define second apertures  782  corresponding to and aligned with apertures  778 , wherein the second apertures  782  are sized and/or shaped to receive the second fastening pins  784 B. The first and second rigid members  516 A,  516 B are securely coupled to either side of the z-bar member  776  via the second fastening pins  784   b  configured to pass through apertures  778  and the second apertures  782  and to retain the first and second rigid members  516 A,  516 B to the z-bar member  776 . 
         [0060]    The second fastening pins  784 B provide fixed pivot points about which the first and second rigid members  516 A,  516 B may pivot. For example, as described above, the release lever  520  may be configured to apply a force to the cammed surface  517  of the first rigid member  516 A via the roller member  786  when the release lever  520  rotates to the second release lever position, such that the first and/or second contact portions  518 A,  518 B move in an inward direction towards to the rail mount body. As the roller member  786  follows the cammed surface  517 , the first rigid member  516 A is forced in an inward direction and rotates about axis  742 A, thereby applying an inward force to left side of the z-bar member  776  at the pivot point created by the second fastening pin  784 B. As the z-bar  776  is forced towards the opposing side, the pivot pivot point on the opposite side of the z-bar member  776  applies an outward force against the second aperture  782  of the second rigid member  516 B. In turn, the second rigid member  516 B is configured to pivot about the pivot point, thereby causing the second rigid member  516 B to rotate about axis  742 B and the contact portion  518 B of the second rigid member  516 B to move in an inward direction toward the rail mount body  514 . The roller member  786  may define an aperture through which a pin  788  may pass and fix the roller member  786  to the release lever  520 . In addition, the release lever  520  may be coupled to the shaft  515  via a washer  790  and a fastener, such as a snap ring  792 . 
         [0061]      FIG. 8  is an isometric view of the rail extension device of  FIG. 7A  mounted to the mounting rail of the firearm of  FIG. 1  showing front and rear scopes attached to the rail extension device with the feed tray cover in the opened position and the rail member in a second rail member position. In the illustrated embodiment, the rail member  408 , coupled with a night vision scope  222 , is in the second rail member position, thereby allowing the feed tray cover  114  to fully rotate to an open position. In the illustrated embodiment the night vision scope  222  does not make any impact with any portion of the receiver assembly  108 . In this instance, the user is not required to remove the night vision scope  222  in order for the feed tray cover  114  to fully rotate to the open position. 
         [0062]      FIG. 9  is a front view of the rail extension device of  FIG. 7A  mounted to the mounting rail of the firearm of  FIG. 1  showing front and rear scopes attached to the rail extension device with the handle and barrel of the firearm alternating between a first position and a second position during a barrel exchange. In the illustrated embodiment, the night vision scope  222  is attached to rail member  408 , wherein the rail member is in the second rail member position, thereby allowing the handle  116  and barrel  102  to fully move from the first to second positions, thus allowing the barrel to be rapidly changed without requiring the user to remove the additional night vision scope  222 . 
         [0063]      FIG. 10  is an isometric view of one embodiment of another rail extension device  600  mounted on the standard rail interface system of the firearm of  FIG. 1  with the feed tray cover  114  in the closed position, consistent with the present disclosure.  FIG. 11  is an alternate isometric view showing a feed tray cover release assembly of the rail extension device of  FIG. 10 ; MG.  12  is an isometric view of the rail extension device of  FIG. 10  mounted on the standard rail interface system of the firearm of  FIG. 1  with the feed tray cover in the opened position;  FIG. 13  is an isometric view of the rail extension device of  FIG. 10  with the rail member in a first rail member position;  FIG. 14  is an isometric view of the rail extension device of  FIG. 10  with the rail member in a second rail member position;  FIG. 15  is an exploded view of the rail extension device of  FIG. 10  with the rail member in the second rail member position;  FIG. 16  is a section view taken through line  1 - 1  in  FIG. 10 ; and  FIG. 17  is an end view of the rail extension device of  FIG. 10 . 
         [0064]    The rail extension device  600  may be secured to the mounting rail  120  of the firearm  100 , e.g. an M240 machine gun, with one or more fasteners  630 . The rail extension device  600  may have a first rail member  602  and a second rail member  604 . The second rail member  604  may rotate about a pin  610 , which may have an axis generally parallel with the longitudinal axis A of the firearm  100 . The second rail member  604  may be movable from a first rail member position shown in  FIG. 13  to a second rail member position shown in  FIG. 14 . The fasteners  630  may extend through washers  632 , brackets  608 A,  608 B, and  608 C in the first rail member  602 . The fasteners  630  may have a clamp  634  coupled to one end with a washers  636  and another fastener  638 . The clamp may have a profile that cooperates with and comes into contact with the mounting rail  120 . Alternatively, the fasteners may incorporate an adjustable over-center mechanism. As shown in  FIG. 16 , one side of the underside of first rail member  602  may also be contoured to cooperate with the profile of the mounting rail  120 . When the fasteners  630  are tightened, the first rail member  602  is coupled to the mounting rail  120 . The underside of the first rail member  602  may have one or more protuberance that cooperate with slot in the mounting rail  120  to resist longitudinal motion. The feed tray cover  114  with the first rail member  602  coupled thereto may rotate about an existing pin  140  from a closed position shown in  FIG. 10  to an open position shown in  FIG. 12 . 
         [0065]    As described above with reference to  FIG. 1 , a user may desire to open the feed tray cover  114 . The operator may rotate a feed tray cover release actuator  670  which may be configured to force first paddle  684  and second paddle  682  inward against locking latches  224  (See  FIG. 5 ) of the feed tray cover  114 , thereby allowing the user to open the feed tray cover  114 . A bracket  680 , pins  686 , and fasteners  688  may be configured to translate the inward rotation of first paddle  684  into an inward rotation of the second paddle  682 . The feed tray cover release actuator  670  may rotate about a member  690  extending from the bracket  680  and may be secured with sleeve  674  and a clip  672 . A protrusion, for example a wheel rotatable about an axis generally parallel with the longitudinal axis A of the weapon  100 , may translate the rotation of the feed tray cover release actuator  670  into linear movement of the first paddle  684  along the member  690 . The bracket  680  may have an opening sized to cooperate with an upstanding portion of the mounting rail  120  to resist longitudinal movement. 
         [0066]    In the embodiment shown in  FIG. 15 , the underside of the bracket  680  may be contoured to cooperate with the profile of the mounting rail  120  and the bracket  680  may be secured to the first rail member  602  with a fastener extending through opening  692  in the bracket  680  and an opening  694  in the first rail member  602 . In another embodiment shown in  FIG. 17 , one of the undersides of a bracket  680 ′ is contoured to cooperate with the profile of the mounting rail  120  and a clamp  634 ′ having a profile that cooperates with and comes into contact with the mounting rail  120  may be secured in place with a fastener  630 ′. 
         [0067]    The rail extension device  600  may include a release trigger  628  rotatably coupled to the second rail member  604  via a fastener  662 . The release trigger  628  may be actuated when the feed tray cover  114  is rotated from the closed position towards the open position. The fastener  662 , for example a pin or screw, inserted through an opening  604 E in the second rail member  604  and an opening  628 A in the release trigger  628  and then into a boss  604 A may rotational couple the release trigger  628  to the second rail member  604 . Rotational movement of the release trigger  628  may be translated into linear movement of a latch  652  that may cooperate with features in the first rail member  602  to secure the second rail member  604  in a “locked” position. A spring  658  or other biasing member may be used to bias the latch towards an engaged position. The spring  658  may be coupled to the latch  652  with one or more fasteners  656  and washers  654 . Pins  660  may couple the latch  652  to the second rail member  604  and allow the latch to travel in a direction parallel with the longitudinal axis A of the weapon  100 . 
         [0068]    When the release trigger  628  is actuated, one or more springs  612 ,  614  or other biasing member(s), may cause the second rail member  604  to rotate about a pivot pin  610  from its first position shown in  FIG. 13  to its second position shown in  FIG. 14 . The pin  610  may extend generally parallel with the longitudinal axis A of the weapon  100  through bosses  602 A on the first rail member  602  and bosses  604 A,  604 B, and  604 C on the second rail member  604 . The linear travel of the pin  610  may restricted by fasteners  616 ,  618  inserted in opposing ends of the pin  610 . 
         [0069]    When an operator wishes to recommence firing of the weapon  100  after reloading ammunition, he or she simply rotates the feed tray cover  114  about the pin  140  and then rotates the second rail member  604  about pin  610 . When the feed tray cover  114  comes into contact with the feed tray  112  the latches  224  will automatically reengage with the feed tray  112  and when the second rail member  604  comes into contact with the first rail member  602 , the latch  652  will reengage with the first rail member  602 . 
         [0070]    While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention. 
         [0071]    All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. 
         [0072]    The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
         [0073]    The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements, that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified, unless clearly indicated to the contrary.