Abstract:
An accessory support for a firearm having a longitudinal barrel, the accessory support comprising an annular body attachable to the barrel or to a rail on the barrel and including an inner surface wherein a portion of the inner surface includes a curved surface, an accessory mounting structure coupled to the annular body for receiving an accessory to the firearm, and a coupling mechanism attached to the annular body to fixedly attach the accessory support to the firearm or rail, wherein the curved surface includes a circumferentially-extending curved recess having opposing lateral surfaces for engaging mating protrusions of a rail mounted on the firearm barrel.

Description:
FIELD OF THE INVENTION 
     This application relates to accessories for firearms. More particularly, embodiments according to this application relate to accessory supports that mount to rail systems that may include one or more accessory rails. 
     BACKGROUND OF THE INVENTION 
     An operator must grip a firearm on or adjacent the barrel to stabilize the firearm during operation. Rail systems can be provided to attach accessories that are available to aid in the proper or enhanced operation of firearms. Further, rail systems can prevent items from directly attaching to the barrel, which can alter the barrel slightly and can adversely affect the accuracy of the firearm. Also, rail systems can protect the hand from the heat of the barrel. 
     Rail systems and/or firearm accessories add weight to the firearm. Accessories and/or accessory mounting devices need to mount securely, easily, and quickly to the rail systems and certain accessories need power to operate. Further, accessory mounting devices must be constructed ruggedly and to withstand heavy use. In addition accessory mounting devices need to be cheap, fast, simple, and accurately manufactured. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an aspect of this application to address in whole or in part, at least the foregoing and other deficiencies in the related art. 
     It is another aspect of this application to provide in whole or in part, at least the advantages described below. 
     It is an object of this application to provide a rotatable accessory mount for use with a firearm, a rail system of a firearm, accessory rail, and/or methods for using the same. It is an object of this application to provide a secure and circumferentially moveable accessory mount and methods thereof. It is an object of this application to provide removable rotatable accessory mounts and/or methods of using the same. It is an object of this application to provide a support device that slidingly moves between a plurality of positions, where an inner surface engages outer surfaces between longitudinally spaced projections of a firearm rail system at each of the plurality of positions and methods thereof. It is an object of this application to provide a rotatable mount including a curved inner surface with a recess or race or cavity that engages curved lower surfaces between and side surfaces of spaced radial projections of a rail system. The curved inner surface can include a recess corresponding to a spaced radial projection of the rail system. 
     In one embodiment, an accessory support for a firearm can include an annular body including an inner surface, a portion of the inner surface includes a curved surface, where an accessory mounting structure coupled to the annular body, and a coupler to fixedly attach the accessory support to firearm. 
     In another embodiment, a mount apparatus for an integrated rail system can include a mount body including an inner surface, an outer surface, a first side surface to connect the inner and outer surfaces, and a second side surface to connect the inner and outer surfaces, an accessory mount coupled to a surface of the mount body, and an engagement portion of the mount apparatus includes a curved portion of the inner surface of the mount body. 
     In yet another embodiment, a method can include forming a mount structure including a curved surface, and attaching the mount structure to an accessory rail system for a firearm using the curved surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Novel features that are characteristic of the embodiments of the application are set forth with particularity in the claims. The application itself may be best be understood, with respect to its organization and method of operation, with reference to the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a diagram that shows a perspective exterior view of an exemplary firearm and rail system; 
         FIG. 2  is a diagram that shows a perspective exterior view of exemplary rail system for use with embodiments of the application; 
         FIG. 3  is a diagram that shows a front end view of an exemplary rail system shown in  FIG. 2 ; 
         FIG. 4  is a diagram that shows a perspective view of another exemplary rail system having a curved surface between tabs of an accessory rail for use with embodiments of the application; 
         FIG. 5  is a diagram that shows a perspective view of an exemplary embodiment of an accessory mount according to an embodiment of the application; 
         FIG. 6  is a diagram that shows a side view of the exemplary embodiment of the accessory mount shown in  FIG. 5 ; 
         FIG. 7  is a diagram that shows an exploded perspective view of the exemplary embodiment of the accessory mount shown in  FIG. 5 ; 
         FIG. 8  is a diagram that shows a top view of the exemplary accessory mount according to an embodiment of the application; and 
         FIG. 9  is a diagram that shows a flowchart of an exemplary method to operate a mount structure according to an embodiment of the application. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Referring to  FIG. 1 , firearm  10  has a barrel  12  extending beyond an exemplary rail system  20 . Rail system  20  can include top rail  22 , side rails  24 , and bottom rail  26 . Rail system  20  can be mounted on firearm  10  by various structures and methods known to one skilled in the art. Rail system  20  can be an integrated accessory rail system that can be extruded as a single piece having each element integrally formed therewith. Alternatively, rail system  20  can be manufactured in a plurality of pieces and assembled before or assembled simultaneously when mounting directly or indirectly to firearm  10 . While rail system  20  can be mounted on a rifle as shown in  FIG. 1 , exemplary rail systems can be mounted on substantially any firearm. Further, embodiments of accessory mounts according to the application can be mounted on substantially any firearm. 
     Any or all of top rail  22 , side rails  24 , and bottom rail  26  can be referred to herein as “rail assembly.” Additionally, while top rail  22 , side rails  24 , and bottom rail  26  are illustrated carried by rail system  20 , some, or all may be omitted as desired. Further, for example, exemplary rails, accessory rails, and/or various rail assemblies described herein such as rail system  20  (and/or rail system  30 , rail system  400 ) can adhere to all the critical dimensions of MIL-STD 1913, and/or Picatinny rail, which is hereby incorporated by reference in its entirety. 
     Referring now to  FIG. 2 , an exemplary rail system  30  can include top accessory rail  32 , side accessory rails  34 , or bottom accessory rail  36 . The following descriptions of exemplary rail system  30  include a description of the various accessory rails. Those skilled in the art will understand that rail system  30  can be used without accessory rails, and conversely, accessory rails can be employed on other rail systems, hand guard systems, or firearms in general. Rail system  30  can include a tubular body  38  that can be spaced from, but surround or cover a portion/majority of barrel  12  of a firearm. Tubular body  38  may be fabricated, for example, by extrusion and subsequent milling. Top accessory rail  32  can be formed manufactured with tubular body  38  and can be used to mount rail system  30  to firearm  10  (e.g., at an upper mount of firearm  10 ). Rail system  30  can, for example, engage a barrel nut of barrel  12  for support. Alternative or additional support can be provided to rail system  30  and/or top accessory rail  32 , if present. 
     In the event that one or all of top accessory rail  32 , side accessory rails  34 , or bottom accessory rail  36  are used without tubular body  38 , they may be attached to a firearm using another rail system or by structures other than a rail system (e.g., attachment rings, hand guards, or other mounting devices). As described herein, structure mounting one or all of the top accessory rail  32 , side accessory rails  34 , and/or bottom accessory rail  36  can be included in the “mounting structure,” which is intended to include any structures mounting one or all of the top accessory rail  32 , side accessory rails  34 , or bottom accessory rail  36  on a firearm, including tubular body  38 . Further, one or all of top accessory rail  32 , side accessory rails  34 , and bottom accessory rail  36  and the mounting structure for the rails can be considered to be in the “rail system” as described herein. 
     Referring to  FIG. 2 , openings  38   a  (e.g., longitudinal slots) can be formed in tubular body  38 , between top accessory rail  32 , side accessory rails  34 , and bottom accessory rail  36  to reduce weight and/or increase air flow between tubular body  38  and the firearm and/or barrel  12 . Openings  38   a  can be formed crossing or within accessory rails. 
     A plurality of equally spaced transverse ribs  33  can be formed on a portion, a majority, or substantially the entire length of top accessory rail  32 , side accessory rails  34 , and/or bottom accessory rail  36  separated or interspaced by a plurality of corresponding recesses  35 . As shown in  FIG. 2 , the recesses  35  of the rail system  30  can have a flat planar bottom surface between adjacent tabs or ribs  33 . Transverse ribs  33  can be used to mount accessories to a firearm and can reduce or prevent movement (e.g., forward, sideways, or rearward) of accessories attached thereto. 
     Referring to  FIG. 3 , a front view of rail system  30  is illustrated. Top accessory rail  32  and side accessory rails  34  are substantially identical; therefore, only top accessory rail  32  will be described in detail herein. Bottom accessory rail  36  is similar to top accessory rail  32  but includes a central longitudinal groove  47  and/or openings  38   a . It is understood that central groove  47  can have different cross-sections (e.g., stepped, angled, tiered, or the like) to provide additional internal referencing surfaces. 
     Referring to  FIG. 3 , top accessory rail  32  can include at least first (e.g., lower) external referencing surfaces  41  and  42 , which can be defined by opposing longitudinal side cuts or grooves  41  and  42 , respectively. Second (e.g., upper) external referencing surfaces  41   b  and  42   b  adjoin first external referencing surfaces  41   a  and  41   b . A third (e.g. top) referencing surface  33   a  can join second referencing surfaces  41   b  and  42   b . Additional external or internal referencing surfaces may be included for an accessory rail. For example, optional internal referencing surfaces  47   a  and  47   b  can be defined by central longitudinal cut or groove  47 . 
     In top accessory rail  32 , side accessory rails  34 , or bottom accessory rail  36 , one or more longitudinally extending conduits (e.g., passageways, tubes)  39  can be provided as shown in  FIG. 3 . Exemplary conduits  39  can pass through one or more of ribs  33 , recesses  35 , tubular body  38  and/or longitudinal slots  38   a ,  38   b . Further, conduits  39  can pass through at least one transverse rib  33 , a plurality of transverse ribs  33 , a majority of transverse ribs  33 , or all transverse ribs  33  in a corresponding accessory rail. 
     Referring to  FIG. 4 , exemplary rail system  400  is similar to exemplary rail system  30 . However, a bottom surface  135   a  between transverse tabs  133  is curved. As shown in  FIG. 4 , transverse tabs  133  can include surfaces  162 , which can be used to mount accessories. Surfaces  162  can be substantially vertical and can include first lateral surfaces  162   a  and second opposing lateral surfaces  162   b  (e.g., forward lateral surfaces and back lateral surfaces  162   b ), which can define recess  135  therebetween. 
     As shown in  FIG. 4 , a bottom surface  135   a  of recess  135  can be curved. For example, the bottom surface  135   a  can have the shape of a portion of a cylindrical surface. Further, an intersection between bottom surface  135   a  of recess  135  and lateral surfaces  162   a  or  162   b  forms a curved or non-linear line  170 . In contrast,  FIG. 2  illustrates of the rail system  30  having a flat lower surface of the recess  35 . 
     Referring to  FIG. 3 , exemplary accessory mounting structures can be detachably held by one or more of external referencing surfaces  41   a ,  41   b ,  42   a ,  42   b  or internal referencing surfaces  47   a ,  47   b . Various types of accessory mounting structures known to one skilled in the art can be used with rail system  30 . 
     Referring to  FIG. 5 , an exemplary embodiment of a rotatable accessory mount is illustrated. As shown in  FIG. 5 , rotatable mount structure  500  includes a curved lower (e.g., inner radial surface) surface  535 . For example, the curved lower surface  535  has a cylindrical shaped that is substantially continuous. In one embodiment, the curved lower surface  535  includes first and second contacting surfaces  535   a ,  535   a ′ separated by at least one recess  533 . The recess  533  can include a first lateral wall  562   a  and an opposing second lateral wall  562   b  that can be separated by connecting surface  533   a . The curved lower surface  535  can be generally configured to interlock (e.g., frictionally fit) with recesses (e.g.,  35 ,  135 ) between tabs (e.g.,  33 ,  133 ) in an integrated rail system or an accessory rail of a rail system. In one embodiment, the first and second contacting surfaces  535   a ,  535   a ′ can implement a matching curvature (e.g., radius or radial circumference) to the curved bottom surface  135   a . Further, the recess  533  can be generally configured to interlock (e.g., frictionally fit) with a corresponding rib  33  (e.g., lateral surfaces  162   a ,  162   b ) from an integrated rail. Alternatively, the recess  533  can be dimensioned to prevent contact between the mount structure  500  (e.g., the recess  533 ) and longitudinal or external surfaces or (e.g.,  41 ,  42 ) a top surface of the ribs  33 . 
       FIG. 6  is a diagram that illustrates a side view of the mount structure  500  of  FIG. 5 . As shown in  FIG. 6 , the mount structure  500  can include an accessory mounting portion  610 , a second fastener or second locking mechanism  620 , an annular section  630  and a first fastener or first locking mechanism  640 . In one embodiment, the second locking mechanism  620  is optional. In one embodiment, the second locking mechanism can be included in the annular section  630 . 
     As shown in  FIG. 6 , the accessory mounting portion  610  can be formed to accommodate any selected standard accessory size or configuration. For example, the accessory mounting portion  610  can have a standard sized footprint, which can cooperatively affix at least one standard accessory type. As shown in  FIG. 5 , the accessory mounting portion  610  can have a standard sized (e.g., 1″, ¾″, ½″) cylindrical footprint, which can satisfy at least one standard accessory type including a helmet camera. However, the accessory mounting portion  610  is not intended to be so limited. For example, other accessories including but not limited to cameras, sights, scopes, flashlights, lasers, infrared devices, recording devices or the like, which can be fit to a standard accessory mount instantiated by accessory mounting portion  610 , can be used. Further, the accessory mounting portion  610  can have alternative standard mounting configurations or shapes (e.g., including rectangular, polygonal, etc.) As shown in  FIG. 5 , the accessory mounting portion  610  can be used to mount any cylindrical accessory with an outer diameter of 0.7 to 1.1 inches (18 to 28 mm). Further, accessories mounted to the accessory mounting portion  610  can be powered by internal sources (e.g., batteries) or external sources using adaptors or cables to supply the power (e.g., via connections to external power sources or batteries). 
     As shown in  FIGS. 5-8 , the first fastener or first locking mechanism  640  can be formed to releasably fasten a first elongated side piece  510 - 1  and a second elongated side piece  510 - 2  together. As shown in  FIG. 5 , the first fastener  640  can be mounted at a distal end of the rotatable mount structure  500  from the accessory mounting portion  610 . However, embodiments of the application are not intended to be so limited. For example, the first fastener  640  can be at any point around the curved lower surface  535  or the annular section  630 . 
     In one embodiment, the first fastener  640  can operate to reciprocally move between first and second positions. In both the first and second positions of the first fastener  640 , the curved lower surface  535  can frictionally engage the rail system at recesses  35 ,  135 . However, in the second position, the mount structure  500  can not be moved (e.g., using unassisted manual force or without damaging the rail system or the mount structure  500 ), and in the first position, the mount structure  500  can rotatably move (e.g., using manual force). For example, in the first position the mount structure  500  can move around a longitudinal axis of the annular section  630  and/or the longitudinal axis of the integrated rail. 
     In the first position, the first fastener  640  can remain connected to both the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2 . Alternatively, in the first position, the first fastener  640  can remain connected to only one of the first and second elongated side pieces. In either exemplary configuration, the first position of the first fastener  640  can produce sufficient dimensional fit or frictional force to support the rotatable mount structure  500  in the rail system to remain in place unless moved by force applied by a user. Alternatively, in the first position of the first fastener  640 , a frictional fit to a corresponding rail system can be negligible so that the mount structure  500  slides freely (e.g., from gravity) in the first position of the first fastener  640 . 
     In one embodiment, in the first position of the first fastener  640 , the second engagement points  512 - 1 ,  512 - 2  ( FIG. 8 ) of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2  are separated by a gap  514  therebetween. In the second position of the first fastener  640 , the second engagement points  512 - 1 ,  512 - 2  of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2  can be adjacent or a size of the gap  514  is reduced relative to the first position of the first fastener  640 . 
     In one embodiment, the first lateral wall  562   a  and/or the opposing second lateral wall  562   b  can frictionally engage corresponding lateral walls  162   a  and  162   b  of the tabs  133  in both of the first and the second positions of the first fastener  640 . Alternatively, the first lateral wall  562   a  and the second lateral wall  562   b  can frictionally engage the lateral walls  162   a ,  162   b  of the tabs  133  in only the second position of the first fastener  640 . 
     As shown in  FIG. 7 , in one embodiment, the first fastener  640  can include a hinge  720  tangentially attached to upper surfaces (e.g., outer surfaces) of the first and second elongated side pieces  510 - 1 ,  510 - 2 . In one embodiment, the hinge  720  can include latch  722  including first pin  722   a , second pin  724 , first link  726  and second link  728 . The first link  726  and the second link  728  are pivotably connected to only the first pin  722   a  or both the first pin  722   a  and the second pin  724 . The first pin  722   a  passes through corresponding holes in first radial projections  732  of the first elongated side piece  510 - 1 . The second elongated side piece  510 - 2  has second radial projections that form a lip  734  at an outer edge of a recess  736  configured to receive the second pin  724  when the mount structure  500  is attached to the integrated rail assembly. For example, the lip  734  can be configured to retain the second pin  724  in just the first position of the first fastener  640  or both the first and second positions of the first fastener  640 . 
     As shown in  FIGS. 5-8 , the second fastener or second locking mechanism  620  can be formed to releasably fasten a first elongated side piece  510 - 1  and a second elongated side piece  510 - 2  together. As shown in  FIG. 5 , the second fastener  620  can be mounted between the annular section  630  and the accessory mounting portion  610 . However, embodiments of the application are not intended to be so limited. For example, the second fastener  620  can be positioned in the annular section  630 . The first fastener  640  and the second fastener  620  are spaced apart from each other on the first and second elongated side pieces  510 - 1 ,  510 - 2 . 
     In one embodiment, the second fastener  620  can operate to reciprocally move between first and second positions. In both positions of the second fastener  620 , the curved lower surface  535  can frictionally engage the lower surfaces of recess  35 ,  135 . However, in the second position of the second fastener  620 , an accessory (e.g., flashlight) mounted in the accessory mounting position  610  is rigidly or lockingly held and cannot be moved (e.g., using unassisted manual force or without breaking the mount structure  500 ). In the first position of the second fastener  620 , the accessory (e.g., flashlight) can move. For example, in the first position of the second fastener  620 , the accessory can be changed. 
     The second fastener  620  corresponds generally to and is intended to reciprocally hold together the first engagement points  516 - 1 ,  516 - 2  of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2 , which are by are separated by a gap  518  therebetween. In the second position of the second fastener  620 , the first engagement points  512 - 1 ,  512 - 2  of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2  are held together, adjacent or a size of the gap  518  is reduced relative to the first position of the second fastener  620 . Alternatively, the first engagement points  516 - 1 ,  516 - 2  can be configured to touch in both positions of the second fastener  620  so that the first fastener  640  alone changes an inner circumferential size of the annular section  630  (e.g.,  535 ). 
     In addition, in the first position of the second fastener  620 , the third engagement points  522 - 1 ,  522 - 2  of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2  are separated by a gap  524  therebetween and fourth engagement points  526 - 1 ,  526 - 2  of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2  are separated by a gap  528  therebetween. In the second position of the second fastener  620 , the third engagement points  522 - 1 ,  522 - 2  and the fourth engagement points  526 - 1 ,  526 - 2  of the first elongated side piece  510 - 1  and the second elongated side piece  510 - 2 , respectively, can be adjacent or a size of the gap  524  and/or the gap  528  can be reduced relative to the first position of the second fastener  620 . 
     As shown in  FIG. 7 , in one embodiment, the second fastener  620  can include a bolt  740  to pass through a corresponding hole  742  in the first elongated side pieces  510 - 1  and engage internal threads  744  in a receiving hole passing through the second elongated side piece  510 - 2 . Alternatively, a nut can be used to reciprocally engage the bolt  740  in the second position of the second fastener  620  and release the bolt  740  in the first position of the second fastener  620 . Other connecting structures are intended for and can be interchangeably used for the first and second fasteners. 
     In one embodiment, the mount structure  500  can include an alternate configuration for the curved lower (e.g., inner radial surface) surface  535  to provide additional contacting surfaces for the lower flat surface  35   a  shown in  FIG. 2 . For example, to controllable align to and provide the additional contacting surfaces with the lower flat surface  35   a  shown in  FIG. 2 , the curved lower surface  535  can include four flat portions (not shown) to correspond with the lower flat surfaces  35   a  on the top, sides and bottom rails. The four flat portions of the curved lower surface  535  can project into the annular section  630  and can have approximately the width of a top surface  33   a  of the rib  33 . Alternatively, the curved lower surface  535  can include a multiple of four (e.g., eight, twelve, sixteen, etc.) flat portions to correspond with the lower flat surfaces  35   a  and to allow additional frictional contact when the mount structure  500  is not aligned directly with the accessory rails (e.g., top, side, or bottom rails) of a rail system, however, a width of the flat portions may be reduced. In another embodiment, the curved lower surface  535  can include a plurality of corner portions, each to align with one of the two ends of each of the lower flat surfaces  35   a . Such exemplary corner portions in the curved lower surface  535  can project away from an interior of the annular section  630  and into the curved lower surface  535 . Each connecting side forming the corner portion of the curved lower surface  535  can have a prescribed dimension. Further, the curved lower surface  535  can include additional corner portions (e.g., eight, ten, twelve, etc) to correspond with the lower flat surfaces  35   a  and to allow additional frictional contact when the mount structure  500  is not aligned directly with the accessory rails (e.g., top, side or bottom rails) of a rail system. 
     In one embodiment, the rotatable mount structure  500  can include an alignment indicator to indicate the accessory mounting portion  610  is accurately aligned with the corresponding accessory rail (e.g., top rail  32 , side rails  34 , or bottom rail  36 ). For example, the alignment indicator can be marking on the forward lateral face of the first and second elongated side piece  510 - 1 ,  510 - 2  in view of the operator. Alternatively, the alignment indicator could be a projection from the rail system that sufficiently engages a portion of the mount structure  500  to be detected or felt by the operator while the mount structure  500  is rotating about the integrated rail. In one embodiment, the alignment indicator can be a longitudinal projection on a top surface  33   a  of the rib  33  having a corresponding shape to the gap  514  so that as the mount structure  500  rotates around the integrated rail the projection slides into an out of the gap  514  to be detected by the operator. When the projection enters the gap  514  the accessory mounting portion  610  is accurately aligned with the opposite rail. Alternatively, the mount structure  500  can include an elastic projection that could engage an adjacent tab  133  (e.g., longitudinal or exterior surface  41 ,  42 ) where the accessory mounting position is accurately aligned. Other structures are possible and intended to be used for the alignment indicator. 
     Mount structure  500  can be fabricated, cast or molded of metal, such as aluminum, titanium, etc., or plastics as known to one skilled in the art. 
     Referring to  FIG. 9 , a flowchart of an exemplary method for attaching a mount structure to an integrated rail system according to embodiments of the application will now be described. The method for attaching a mount structure of  FIG. 9 , will be described using and can be applied to the mount structure  500 ; however, the method of  FIG. 9  is not intended to be limited to the mount structure  500 . 
     Referring to  FIG. 9 , after a process starts, a camera or flashlight can be mounted into the accessory mounting portion  610  and locked into place using the second fastener  620  (operation block  910 ). Then, the accessory mount structure (e.g., rotatable)  500  can be attached to an integrated rail assembly with the hinge  720  in the first position (operation block  920 ). The camera can be oriented to the top accessory rail  32  by the operator or using the alignment indicator of the mount structure  500  (operation block  930 ). The mount structure  500  can be locked in place by moving the hinge  720  or the latch  722  into its second or locking position (operation block  940 ). To mount a scope (e.g., different accessory) on the top rail  32 , the operator can move the hinge  720  or the latch  722  to its first position and the locked camera can be rotated with the mount structure  500  to a side rail  34  (operation block  950 ), aligned to the side rail  34  (operation block  960 ), and locked into place by moving the hinge  720  to its second position (operation block  970 ). Then the scope can be attached to the top rail  32  and not be obstructed (operation block  980 ). From operation block  980 , the process can end. Although described in sequence, it is understood that operations described in the method of  FIG. 9  can be performed in various sequences or in parallel. 
     In one embodiment, the rotatable mount structure  500  can be quickly moved from an orientation of a mounted accessory to a first side rail  34  (e.g., left side) to an orientation of the mounted accessory to the opposite side rail  34  (e.g., right side). Switching the mounted accessory from one side of firearm to the other can reduce clearance needed for the firearm and operator when rounding a corner, entering a room, passing thorough a doorway, etc. by valuable inches depending on whether the operator is acting from the right side or the left side when the operation (e.g., entering the doorway) is performed. 
     In one embodiment, the mount structure  500  can include a curved surface for mounting to a firearm and a coupling mechanism. The coupling mechanism can move between a first position to rigidly attach the mount structure to the firearm, a second position to slidingly attach (e.g., rotational movement) the mount structure  500  to the firearm, and a third position to detach the mount structure from the firearm. The first and second position of the coupling mechanism can use the curved surface. The coupling mechanism for the mount structure can include a single fastener or a single locking mechanism. Alternatively, the coupling mechanism for the mount structure  500  can include at least two fasteners or two locking mechanisms. 
     In one exemplary rail system, a bottom surface of recesses formed between opposing lateral faces have a curved surface (e.g., a convex surface when viewed from a front/back perspective). The curvature of a bottom surface between opposing lateral faces can be related to the radial size of rail system unitary body. Reduced debris in the recess can result because the curved or sloped bottom surface can trap less debris and/or previously trapped debris will be forced or urged out of the recess by the slope or curvature. 
     Although grooves  41 ,  42 , and/or  49  are illustrated as a single groove or cut, a plurality of cuts or grooves may be used, for example, to define various surfaces  41   a ,  41   b . Further, longitudinal grooves  41  and/or  42  can define a plurality of additional external referencing surfaces, for example, a fourth external reference surface can be located between first and second external referencing surfaces  41   a  and  41   b  or  42   a  and  42   b . Alternatively, additional external referencing surfaces can be below first external referencing surfaces  41   a  or  42   a.    
     Although embodiments of the application have been described with respect to symmetric and separate first and second elongated side pieces, embodiments are not intended to be so limited. For example, exemplary mount structure embodiments can be formed as single integral piece. In one embodiment, the gap  518 , the gap  524 , and the gap  528  the accessory mounting portion  610  can be eliminated. In one embodiment, just the gap  524  and the gap  518  can be eliminated. In one embodiment, just the gap  528  can be eliminated. In one embodiment, the gap  528  can be replaced with a pivoting fastener such as a hinge. Further, the separate first and second elongated side pieces do not need to be symmetric. In one embodiment, the first elongated side piece could form more than half (e.g. ¾) of the annular section and the second elongated side piece can form less than half (e.g., ¼) of the annular section. 
     Although embodiments of the application have been described with respect to a hinge as a first fastener or locking mechanism, embodiments are not intended to be so limited. For example, the first fastener can be a coupler such as but not limited to a releasable connector, a hinge, a joint, a juncture, a pivot, a two position connector, a one-handed operational configuration. In addition, for example, the first fastener can be a coupler such as but not limited to a releasable connector, a hinge, a joint, a juncture, a pivot, a two position connector, or having a one-handed operational configuration. 
     While the present invention has been described with reference to a number of specific embodiments, it will be understood that the true spirit and scope of the invention should be determined only with respect to claims that can be supported by the present specification. Further, while in numerous cases herein wherein systems and apparatuses and methods are described as having a certain number of elements it will be understood that such systems, apparatuses and methods can be practiced with fewer than the mentioned certain number of elements. Also, while a number of particular embodiments have been set forth, it will be understood that features and aspects that have been described with reference to each particular embodiment can be used with each remaining particularly set forth embodiment.