Patent Publication Number: US-10309748-B2

Title: Firearm rail/handguard and mounting system

Description:
FIELD OF THE INVENTION 
     The disclosure relates to the field of firearm accessories, and, more specifically, to an assembly for mounting a modular rail assembly to a firearm which maintains proper alignment of the assembly with the firearm barrel. 
     BACKGROUND OF THE INVENTION 
     In the general field of combat and commercial weaponry, there is a broad range of accessories available for mounting onto standard firearms in order to upgrade the capability of these weapons. Of particular interest in the context of upgrade accessories is the M16/M4 weapon system that is typically utilized in military or combat settings. Most new models of the M16/M4 weapons also include a dovetail rail interface integrally formed along the top of the upper receiver. This interface rail provides a convenient mounting point for many of the available accessories for use with the M16/M4 firearm, such as scopes, sighting devices, lasers, and directed fire devices. The barrel is held in assembled relation with the upper receiver by a barrel nut that is threaded onto the outside surface of the barrel-receiving receptacle. 
     Some commercially available after market rail/handguard assembly systems require permanent modification of the firearm, such as replacing the original barrel nut with a proprietary barrel nut design, before installation thereof, while others are compatible with the existing configuration of the barrel nut provided by the manufacturer. Either way, it is critical during the installation and use of the firearm rail/handguard assembly that the alignment of the rail/handguard assembly longitudinally, axially, and radially relative to the axis of the barrel bore be free from slippage, canting, or other angular displacements, lest accessories such as scopes securable to the firearm rail/handguard assembly not provide true aiming of the firearm. 
     It would therefore be useful to provide a modular rail/handguard assembly for use with a firearm that prevents any of longitudinal, axial, or radial misalignment of the modular rail assembly relative to the barrel of the firearm at the time of installation. 
     It would be further useful to provide a modular rail/handguard assembly for use with a firearm which prevents any of longitudinal, axial, or radial misalignment of the modular rail assembly relative to the barrel axis of the firearm during use. 
     BRIEF SUMMARY OF THE INVENTION 
     Disclosed is an assembly for mounting a modular rail/handguard to a firearm which maintains proper alignment of the modular rail assembly with the firearm barrel. In particular, the disclosure is directed to an improved mounting configuration for attaching the modular rail/handguard assembly to the barrel nut of a firearm in a manner that prevents any of longitudinal, axial, or radial misalignment of the modular rail handguard assembly relative to the barrel of the firearm. The assembly utilizes a biasing element disposed intermediate the barrel nut and the interior end of the handguard and a clamping element also disposed intermediate the barrel nut and the interior end of the handguard but positioned opposite the biasing element about the perimeter of the barrel nut. One or both of the biasing element and clamping element have multiple surfaces which mimic portions of the exterior profile of the barrel nut to prevent any of longitudinal, axial, or radial misalignment of the handguard relative to the axis of the firearm barrel. 
     According to one aspect of the disclosure, an assembly apparatus for securing a handguard to a firearm having a barrel nut, the assembly apparatus comprises: a handguard having a first end with an interior diameter shaped to receive at least a portion of an exterior of the barrel nut; a biasing element disposable intermediate the barrel nut and the interior diameter of the handguard, the biasing element having first and second biasing surfaces disposable adjacent first and second exterior surface portions, respectively, of the barrel nut; a first mechanism for securing the biasing element intermediate the handguard and the barrel nut, a clamping element having first and second surfaces disposed adjacent first and second exterior surface portions, respectively, of the barrel nut; and a second mechanism for securing the clamping element intermediate the handguard and the barrel nut. 
     In one embodiment, the biasing element prevents movement of the handguard longitudinally along the axis of the barrel. In another embodiment, one or both of the biasing element and clamping element have arcuate surfaces disposed adjacent the exterior perimeter of the barrel nut and prevent radial and/or rotational movement of the barrel nut within the interior of the handguard end. 
     According to another aspect of the disclosure, an assembly kit for use with a firearm having a barrel nut and a handguard, the kit comprising: a biasing element disposable intermediate the barrel nut and an interior diameter of the handguard; a first mechanism for securing the biasing element intermediate the handguard and the barrel nut, a clamping element having first and second surfaces disposed adjacent first and second exterior surface portions, respectively, of the barrel nut; and a second mechanism for securing the clamping element intermediate the handguard and the barrel nut. 
     According to yet another aspect of the disclosure, an assembly apparatus for securing a handguard to a firearm, the firearm having a barrel nut with an exterior perimeter, the assembly apparatus comprises: a handguard having a first end with an interior diameter shaped to receive at least a portion of the exterior portion of the barrel nut; and a first clamping element disposable intermediate the interior diameter of the handguard and a first location on the exterior perimeter of the barrel nut, the first clamping element having an arcuate surface with a first radius of diameter and disposable adjacent the first location on the exterior perimeter of the barrel nut, a second clamping element disposable intermediate the interior diameter of the handguard and a second location on the exterior perimeter of the barrel nut opposite the first location, the second clamping element having an arcuate surface with the first radius of diameter and disposable adjacent the second location on the exterior perimeter of the barrel nut, wherein one of the first and second clamping elements has a second arcuate surface having the second radius of diameter and disposable adjacent the exterior perimeter of the barrel nut. 
     According to yet another aspect of the disclosure, a method for mounting a handguard to a firearm having a cylindrical barrel nut, the method comprises: A) disposing a first end of the handguard about a portion of the barrel nut; B) inserting a biasing element intermediate the first end of the handguard and the barrel nut at a first location about an exterior perimeter of the barrel nut; C) inserting a clamping element intermediate the first end of the handguard and the barrel nut at a second location opposite the first location about the exterior perimeter of the barrel nut, the clamping element having first and second surfaces disposed adjacent first and second exterior surface portions, respectively, of the barrel nut; and D) urging the clamping element against the barrel nut. 
     For a better understanding of the invention, its operating advantages, and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a front, end-on view of an embodiment of the mounting assembly in accordance with the disclosure; 
         FIG. 2  is a side, plan view of an embodiment of the mounting assembly system in accordance with the disclosure; 
         FIG. 3  is a top plan view of an embodiment of the mounting assembly system in accordance with the disclosure; 
         FIG. 4  is a bottom, plan view of an embodiment of the mounting assembly system in accordance with the disclosure; 
         FIG. 5  is a top, perspective view of the embodiment of  FIGS. 1-4  in accordance with the disclosure; and 
         FIG. 6  is a bottom, perspective view of the embodiment of  FIGS. 1-4  in accordance with the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1-6  illustrate embodiments of the modular assembly  10  for mounting to a rail/handguard in accordance with the disclosure. The mounting assembly  10  comprises a handguard  16 , optional barrel nut  12  and mounting system  15 . Handguard  16  is the structural element that supports the entire assembly and serves to transfer the loads or additional weight induced by any attachments onto the upper receiver of the firearm. Mounting system  15  comprises a clamping element  14  and biasing element  18 , as well as their respective attachment mechanisms, which are mechanically coupled intermediate barrel nut  12  and handguard  16 , as described herein in greater detail. 
     As illustrated in the Figures, a cylindrical barrel nut  12  extends longitudinally along an axis  20  and has an exterior perimeter defining first and second exterior surface portions  12 A and  12 B with different exterior diameter values relative to the axis. In the illustrative embodiment, the transition between the diameters of portions  12 A and  12 B is abrupt, causing a step down in the diameter of the barrel nut exterior perimeter. In embodiments, barrel nut  12  may have other exterior perimeter surface features as may be designed by the manufacturer of the handguard. Handguard  16  has a first end  16 A with an interior diameter  16 B shaped to receive at least a portion of one of the first and second exterior barrel nut portions  12 A and  12 B thereagainst. 
     Biasing element  18  is disposed intermediate the barrel nut  12  and the interior diameter  16 B of the handguard  16  and has first and second biasing surfaces  18 A and  18 B disposed adjacent the first and second exterior surface portions  12 A and  12 B, respectively, of the barrel nut  12 . Biasing element  18  has, in the illustrative embodiment, a generally U-shaped cross-sectional profile as seen in a plane normal to axis  20 . In embodiments, the surfaces of biasing element  18  disposed adjacent the exterior perimeter of barrel nut  12 , including one or both of first and second biasing surfaces  18 A and  18 B, may be arcuate in shape with substantially the same degree of curvature as exterior perimeter portion of barrel nut  12  against which they are disposed. In the illustrative embodiment, biasing element  18  is disposed opposite clamping element  14  about the interior of inner diameter  16 B of handguard  16  and is seated in an indentation in the interior surface of inner diameter  16 B. Two pairs of axially aligned apertures extending at least partially through both biasing element  18  and handguard  16  may accept a fastener  22  or other fastening mechanisms for securing the biasing element  18  intermediate the handguard  16  and the barrel nut  12 , as illustrated in the Figures. 
     Clamping element  14  is also disposed intermediate the barrel nut  12  and the interior diameter  16 B of the handguard  16 . In the illustrative embodiment, clamping element  14  may have a generally L-shaped length profile, as seen along an axis parallel to axis  20 , and may have a generally solid cross-sectional profile, as seen from a plane normal to axis  20 , with first and second clamping surfaces  14 A and  14 B disposed adjacent the exterior perimeter of barrel nut  12 . Clamping surfaces  14 A and  14 B may be arcuate in shape with substantially the same degree of curvature as exterior perimeter portion of barrel nut  12  against which they are disposed. In the illustrative embodiment, exterior perimeter portion of barrel nut  12  against which clamping surfaces  14 A and  14 B are disposed may be knurled or contain other surface features to enhance frictional engagement therebetween. Clamping element  14  is disposed opposite biasing element  18  about the interior of inner diameter  16 B of handguard  16  (and the exterior perimeter of barrel nut  12 ) and is seated in an indentation in the interior surface of inner diameter  16 B. A pair of axially aligned apertures extending at least partially through clamping element  14  and handguard  16  may accept a screw  24  or other fastening mechanism for securing the clamping element  14  intermediate the handguard  16  and the barrel nut  12 , as illustrated in the Figures. 
     In embodiments, clamping surfaces  14 A and  14 B of clamping element  14  and biasing surfaces  18 A and  18 B of biasing element  18  are arcuate with a radius of curvature which substantially mimics the radius of curvature of the exterior surfaces of the perimeter of barrel nut  12 . In the illustrative embodiment, barrel nut  12  may have multiple different exterior diameters, as illustrated, accordingly one or both of biasing element  18  and clamping element  14  may have multiple arcuate surfaces with respective radii of curvature which substantially mimic the respective radii of curvature of the exterior surfaces of the perimeter of barrel nut  12  to prevent any of longitudinal, axial, or radial misalignment of the handguard relative to the axis of the firearm barrel. 
     Because clamping element  14  mimics the abrupt transition between the diameters of barrel nut  12  between surfaces  12 A and  12 B, the longitudinal profile of clamping element  14  along axis  20  is generally L-shaped and prevents of longitudinal misalignment of the handguard assembly relative to axis  20  of barrel nut  12  at the time of installation and during use. Similarly, because clamping surfaces  14 A and  14 B of clamping element  14  have arcuate surfaces that mimic the respective curvatures of surfaces  12 A and  12 B of barrel nut  12  with which contact is made, axial and/or radial misalignment of the handguard  16  relative to barrel nut  12  is prevented at the time of installation and during use. 
     A method for mounting the handguard  16  to a firearm having a cylindrical barrel nut  12  comprises disposing a first end of the handguard  16  about a portion of the barrel nut; B) inserting a biasing element  18  intermediate the first end of the handguard  16  and the barrel nut  12  at a first location about an exterior perimeter of the barrel nut and then inserting a clamping element  14  intermediate the first end of the handguard and the barrel nut at a second location opposite the first location about the exterior perimeter of the barrel nut. The clamping surfaces  14 A and  14 B are disposed adjacent first and second exterior surface portions, respectively, of the barrel nut  12 . Once biasing element  18  is seated intermediate handguard  16  and barrel nut  12 , screw  24  can be used to force biasing element  18  securely against the barrel nut  12 . Similarly, once clamping element  14  is seated intermediate handguard  16  and barrel nut  12 , fasteners  22  can be used to force clamping element  14  securely against the barrel nut  12 . 
     Handguard  16  may be formed generally as a tubular enclosure that is configured to encircle the barrel of the firearm when assembly  10  is installed on the firearm in a mounted position. In the illustrative embodiments, handguard  16  has a unitary or monolithic construction defined by left and right side walls that extend between ends thereof and generally outwardly and downwardly in an arcuate manner from an integrally formed top dovetail rail to form a substantially cylindrical body. Top dovetail rail extends at least partially longitudinally between the forward end and the rearward end. An optional supplemental dovetail rail interface may be slidably attached to the bottom of handguard  16  utilizing an integrally formed projection having a complementary mating cross-sectional profile. 
     In the embodiments, any elements of assembly  10  and mounting system  15  may be formed of substantially rigid materials including steel, stainless steel, aluminum, ceramics, or other materials capable of withstanding heat generated by the barrel nut  12  during use of the firearm. 
     As illustrated in the Figures, side walls of the handguard  16  may have a plurality of wall vents extending therethrough to facilitate cooling of the firearm barrel by allowing heated air from the interior of handguard  16  to escape through the vents. It will be obvious to those reasonably skilled in the art that any configuration or shape of sidewall vents, including an open lattice structure, may partially define one or both of sidewalls. It will be further obvious to those reasonably skilled in the art that handguard  16  may have other cross-sectional profiles, such as a pentagon or octagon or other configuration. In addition, although handguard  16  in the illustrative embodiment forms an integral sleeve-like structure, it is contemplated herein that one or more constituent components thereof may be separately assembled into a sleeve-like structure which is insertable over the open end of the barrel. 
     In embodiments, fasteners  22  may be implemented with a helicoil inserts and threaded fastening mechanisms. The helicoil inserts may have threaded exteriors for coupling with threaded interiors of apertures which extend through the handguard  16 . The helicoil inserts may also have a threaded interior which can couple with the threaded exterior of a fastening mechanisms or screw. In some cases, such helicoil inserts may be formed from a stronger and more rigid material than the handguard  16  (i.e., steel versus aluminum) to prevent the handguard  16  from warping, crushing, or otherwise deforming due to force through the fastening mechanisms. In embodiments, the lower surfaces of the fastening mechanisms and the surfaces on clamping element  14  with which they have contact may be flat to maximize contact area. While the fasteners  22  illustrated with regard to the illustrative embodiments have been shown to be helicoil inserts, other fastening mechanisms may be equivalently substituted, including conventional threaded screws such as screws  24 . 
     While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.