Abstract:
Disclosed is an integral firearm sound suppressor, comprising a barrel, a first tube, and interior connector, a baffle tube, and at least one baffle. The barrel has an axial bore, a chamber end, and a muzzle end. The chamber end is attachable to a receiver by the barrel nut. The first tube extends forwardly of the barrel nut to define an annular first chamber at least partially surrounding the barrel and having a closed forward end. The barrel has at least one port providing fluid communication between the bore and the first chamber. The interior connector supports the muzzle end of the barrel. The baffle tube extends forwardly of the muzzle end of the barrel and has a forward end wall defining an exit opening. The at least one baffle is positioned in the baffle tube and spaced forward of the muzzle end of the barrel.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 62/206,894, filed Aug. 19, 2015, and incorporates the same herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to an integral firearm sound suppressor, and particularly one used with an AR15-pattern upper receiver in which the barrel is mounted to the upper receiver using a barrel nut. More particularly, it relates to an integral firearm sound suppressor, especially for use with pistol caliber ammunition, in which an outer tube of the suppressor is integrally formed with the barrel nut and in which both ends of the barrel may be supported by the outer tube and in tension. 
       BACKGROUND OF THE INVENTION 
       [0003]    AR15-pattern firearms, in rifle or pistol configuration, have become extraordinarily popular, in part because of how easily they may be adapted to a variety of configurations, types of actions, and barrel/caliber combinations. A sound suppressor for this type of firearm, whether muzzle-mounted or integral in design, is typically mounted on and supported by the barrel. In pistol caliber configurations, shorter barrels (under 16 inches) are often desirable for a variety of reasons. However, under current federal law, a rifle having a barrel shorter than 16 inches with an integral suppressor typically requires two National Firearms Act (NFA) tax stamps for each transfer (one for the short barrel rifle and one for the sound suppressor). 
         [0004]    Another possible problem with combining a relatively short barrel and integral suppressor, especially in pistol caliber configurations, is that unburned powder could accumulate in the suppressor baffles. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides an integral suppressor for use with a relatively shortened barrel, particularly but not exclusively for center fire, pistol caliber rounds that can support the barrel in tension and attach the barrel to the upper receiver with a barrel nut that is an integral part of the suppressor housing. 
         [0006]    Disclosed is an integral firearm sound suppressor, comprising a barrel, a first tube, and interior connector, a baffle tube, and at least one baffle. The barrel has an axial bore, a chamber end, and a muzzle end. The chamber end is attachable to a receiver by the barrel nut. The first tube extends forwardly of the barrel nut to define an annular first chamber at least partially surrounding the barrel and having a closed forward end. The barrel has at least one port providing fluid communication between the bore and the first chamber. The interior connector supports the muzzle end of the barrel. The baffle tube extends forwardly of the muzzle end of the barrel and has a forward end wall defining an exit opening. The at least one baffle is positioned in the baffle tube and spaced forward of the muzzle end of the barrel. 
         [0007]    The connector can define a forward closed end of the first annular chamber. A blast wall may be spaced forwardly from the muzzle end of the barrel and form a blast chamber. According to one embodiment, the blast wall may include a close passageway axially aligned with the bore and spaced forwardly from the muzzle end of the barrel with a diameter providing close clearance of a projectile to be fired. The length of the close passageway may be at least 0.75 times length of projectile to be fired and may be in the range of approximately 0.75 to 2.5 times length of projectile to be fired. 
         [0008]    The first tube may be integral with or permanently affixed to the barrel nut. The baffle tube may be integral with or permanently affixed to the first tube. Such a configuration can be used to provide an overall length of the barrel assembly that meets minimum legal requirements. 
         [0009]    The connector can be threaded to the muzzle end of barrel and can abut an internal shoulder when assembled. This allows the barrel to be placed in tension by tightening of the connector on the muzzle end of the barrel. 
         [0010]    The port may be positioned in a rearward portion of the first chamber. In one embodiment, there may be multiple, axially spaced apart ports. This can cause multiple interfering pressure waves to form in the first chamber when a projectile is fired and before the projectile exits either the muzzle of the barrel or before it passes completely through the close passageway. 
         [0011]    Other aspects, features, benefits, and advantages of the present invention will become apparent to a person of skill in the art from the detailed description of various embodiments with reference to the accompanying drawing figures, all of which comprise part of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0012]    Like reference numerals are used to indicate like parts throughout the various figures of the drawings, wherein: 
           [0013]      FIG. 1  is a top plan view of an integral suppressor according to one embodiment of the present invention; 
           [0014]      FIG. 2  is a longitudinal sectional view thereof taken substantially along line  2 - 2  of  FIG. 1  as mounted on an upper receiver; 
           [0015]      FIG. 3  is an isometric longitudinal section taken substantially along line  2 - 2  of  FIG. 1 ; 
           [0016]      FIG. 4  is a fragmentary longitudinal sectional view enlarged to illustrate the primary chamber surrounding the barrel; and 
           [0017]      FIG. 5  is an isometric exploded view thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    With reference to the drawings, this section describes particular embodiments and their detailed construction and operation. Throughout the specification, reference to “one embodiment,” “an embodiment”, or “some embodiments” means that a particular described feature, structure, or characteristic may be included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the described features, structures, and characteristics may be combined in any suitable manner in one or more embodiments. In view of the disclosure herein, those skilled in the art will recognize that the various embodiments can be practiced without one or more of the specific details or with other methods, components, materials, or the like. In some instances, well-known structures, materials, or operations may not be shown or described in detail to avoid obscuring aspects of the embodiments. 
         [0019]    Referring now to the various figures of the drawing, and first to  FIGS. 1-3 , therein is shown at  10  an integral, barrel-nut-mounted firearm sound suppressor according to an embodiment of the invention. An outer housing of the suppressor  10  may include a barrel nut portion  12  and a forward tube  14 . The barrel nut portion  12  secures a barrel  16  to the threaded attachment  18  at a forward end of an upper receiver  20  in an otherwise well-known and ordinary manner. According to one aspect of the present invention, when the barrel  16  is less than sixteen inches in length and is to be configured as a rifle, the barrel nut portion  12  and forward tube  14  may be integrally formed or otherwise permanently fixed together, together creating an extension greater than sixteen inches in length and that is essential to assembly of the barrel  16  to the receiver  20 . In this manner, when assembled as a rifle, it will not be considered a “short barreled rifle” (SBR), which is currently regulated under the National Firearms Act (NFA) separate from sound suppressors, thus otherwise requiring payment for two transfer tax stamps. 
         [0020]    According to one embodiment, the barrel  16  may be externally threaded  22  at a forward end thereof. An interior connector or coupling nut  24  may be sized to be slidably received within the forward tube  14 , to have internal threads that mate with the threaded forward portion  22  of the barrel  16 , and to bear against an internal annular shoulder  26  of the barrel nut portion  12 . The coupling nut  24  can be rotated within the forward tube  14 , such as with a non-round tool socket  28 , thereby applying longitudinal tension to the mounted barrel  16 . In this manner, rather than having a barrel support a sound suppressor, as is the usual case, the barrel  16  of the present invention is attached to the receiver  20  and supported by the external body of the sound suppressor  10 . Perfect alignment between the barrel and suppressor can be maintained, as well, because part of the suppressor housing is supporting and controlling both ends of the barrel  16 . 
         [0021]    Referring now in particular to  FIG. 4 , it can be seen that the barrel  16  includes a chamber  30  sized to receive an ammunition cartridge (not shown) and a rifled bore  32 . The barrel  16  is held securely to the upper receiver  20  by threaded engagement of the barrel nut portion  12  to the threaded attachment  18  of the receiver  20 . Orientation of the barrel  16  is maintained in a well-known manner by a key pin  34  that engages a notch in the threaded portion  18 . Thus, the barrel  16  is held against rotation as the barrel nut portion  12  is tightened onto the receiver  20 . A forward tubular extension  36  of the barrel nut portion  12  may be spaced away from the barrel  16  to provide an annular first or primary chamber  38  substantially surrounding at least a portion of the barrel  16 . The forward end of this primary chamber  38  may be closed by the coupling nut  24  that engages the threads  22  at the forward end of the barrel  16  and the internal annular shoulder  26 . Again, the barrel  16  is restrained from rotation by the key pin  34  as the coupling nut  24  is threaded onto the barrel  16  and tensioned. 
         [0022]    According to another feature of the invention, at least a pair of axially spaced-apart ports  40 ,  42  may be provided in the barrel  16  to provide fluid communication between the bore  32  and primary chamber  38 . In the illustrated embodiment, the aft port  40  may be a series of radial openings, such as four openings circumferentially spaced at about  90  degrees from each other. Also in the illustrated embodiment, the forward port  42  may be a pair of radially extending, opposed openings. Thus, in the illustrated embodiment, the aft port  40  provides approximately twice the fluid communication of the forward port  42 . The fluid communication can be controlled by the number and/or relative size of the openings comprising each port  40 ,  42 . In the illustrated embodiment, these ports  40 ,  42  are positioned relatively aftwardly along the length of the bore  32  such that propulsion gases behind a projectile can vent into the primary chamber  38  before the projectile has left the bore  32  of the barrel  16 . If desired, the length of the barrel  16 , volume of the primary chamber  38 , and position/size of the ports  40 ,  42  may be selected such that the cartridge propellant is substantially fully burned and propulsion gases fully expanded just as the projectile reaches the forward end of the bore  32  at the muzzle  43 . These parameters may also be selected to cause the projectile velocity to remain subsonic, further reducing the resulting perceived sound level. 
         [0023]    When a pressure wave passes along a closed end chamber, the pressure wave may be reflected back when it encounters the closed end of the chamber. Multiple pressure waves can interfere or resonate to produce a standing wave in such a chamber. The rapidly burning propellant from a firearm cartridge, however, typically acts as only a single pressure wave. Referring again to  FIG. 4 , as a pressure wave of expanding gasses enters the primary chamber  38  through the aft port  40 , a pressure wave begins to travel forwardly through the annular primary chamber  38 . Depending upon the duration of the pressure wave, it can be reflected back upon reaching the forward, closed end  47  of the primary chamber  38 . It is believed that expanding gasses entering the chamber  38  through the forward port  42  can create a separate, and slightly delayed, pressure wave within the primary chamber  38 , particularly if the expansion of propellant gases can be timed to end just as the projectile reaches a muzzle end  43  of the barrel  16 . Interfering pressure waves in the primary chamber  38  can be sufficient to cause a momentary delay in evacuation of the high pressure propulsion gases from the chamber  38 , back through the ports  40 ,  42 , and into the bore  32 . This momentary delay can be sufficient to allow a significant amount of energy to be consumed by heat transfer and turbulence caused by the reversal of flow, significantly reducing the perceived noise resulting from the pressure wave of the propellant blast. 
         [0024]    Immediately forward of the coupling nut  24  can be a blast baffle  44 . According to the illustrated embodiment, the blast baffle  44  includes an annular chamber  46  which, together with the tool socket  28  of the coupling nut  24 , provides an expansion chamber immediately forward of the muzzle. The blast baffle  44  may include rearwardly oriented nozzle  45  with a central close passageway  48  that is axially aligned with the bore  32  of the barrel  16 . This passageway  48  may have a diameter that is only slightly greater than that of the projectile, such that a relatively close clearance is provided while assuring no contact is made between the projectile and walls of the passageway  48 . According to another aspect of the invention, the central passageway  48  may have an axial length equal to at least 0.75 times the length of a projectile expected to be used with the suppressor  10 . If desired, the longitudinal length of the central passageway  48  may be from about 0.75 to about 2.5 times the length of the projectile to be used. By providing a relatively close fit and extended passageway length, the time required for the projectile to clear the central passageway  48  can be sufficient to allow significant expansion and corresponding reduction in pressure of the propellant gases escaping from the muzzle  43  and cause a momentary delay before the gases are free to flow through the central passageway  48 . 
         [0025]    As shown in  FIGS. 2, 3, and 4 , a series of baffles  50  may be provided forward of the blast baffle  44  along the remaining length of the forward tube  14 . These baffles  50  and blast baffle  44  may be held in place by a threaded end cap  52  having a central passageway  54  axially aligned with the bore  32  of the barrel  16 , the central passageway  48  of the blast baffle  44  and central openings in each of the forward baffles  50 . Although the illustrated baffles  50  are what may be known as an “M-baffle,” other baffle shapes (such as, but not limited to, K-baffles or cone baffles) may be used and the exact design and/or number of the forward baffles  50  is not essential to the present invention. In fact, the illustrated stack of twenty baffles  50  is likely to be greater in number than required to effectively suppress the sound of most center-fire, pistol caliber rounds, particularly at subsonic velocity. However, if the forward tube  14  is extended to provide a permanent overall barrel length greater than sixteen inches, there is no performance penalty, and relatively trivial added weight and cost, to filling the forward tube  14  with a full series of baffles  50 . 
         [0026]    Referring now in particular to  FIGS. 1 and 5 , the integral suppressor  10  may be assembled as follows: 
         [0027]    The barrel nut portion  12  and forward tube  14  of the outer housing may be integrally formed, separable parts, or permanently fixed together, such as by welding, bonding, or locking a threaded engagement with a lock pin (not shown). The barrel  16  may be seated against the threaded attachment portion  18  of the upper receiver  20  and held in place by threading the barrel nut portion  12  onto the receiver  20 . The coupling nut  24  may be inserted through the forward open end of the tube  14  and then rotated to threadingly engage exterior threads  22  at the forward end of the barrel  16 . The coupling nut  24  may be rotated, such as with an elongated tool (not shown) inserted into the tube  14  into engagement with the non-round (such as hexagonal) tool socket  28 . The coupling nut  24  can be threaded into place until it contacts the internal annular shoulder  26  and exerts a desired longitudinal tension on the barrel  16 , holding the barrel  16  firmly in place and in alignment relative to the outer housing  12 ,  14 . The blast baffle  44  and stack of sound suppression baffles  50  may then be inserted into the forward tube  14  and secured with the threaded end cap  52 . If desired, a hand guard (not shown) may be installed over the suppressor  10 , such as with fasteners that interface with threaded sockets  56  provided on an exterior surface of the barrel nut portion  12 . 
         [0028]    While one or more embodiments of the present invention have been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. Therefore, the foregoing is intended only to be illustrative of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not intended to limit the invention to the exact construction and operation shown and described. Accordingly, all suitable modifications and equivalents may be included and considered to fall within the scope of the invention.