Patent Publication Number: US-2018038664-A1

Title: Apparatus and method of removing a gas block without removing attached muzzle device

Description:
RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 62/371,896, filed Aug. 8, 2016, and incorporates the same herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an apparatus and method that allows removal of a gas block from the barrel of a gas operated semi-automatic firearm without removing an attached muzzle device, such as a flash suppressor or muzzle brake. 
     BACKGROUND OF THE INVENTION 
     In a gas operated semi-automatic firearm, a portion of the propulsion gas which drives a projectile through the barrel bore is bled off through a gas port in the barrel. The energy of this gas pressure is used to cycle the action of the firearm, either by direct impingement or a gas piston. 
     A gas block is mounted on the barrel at the location of the gas port to direct the ported gas flow through a passageway in the gas block to a gas tube or piston. Typically, the gas block is assembled to the barrel by sliding a bore opening in the gas block over the muzzle end of the barrel and moving it rearwardly (toward the chamber end of the barrel) until the gas block&#39;s passage way is aligned with the gas port in the barrel. Needing to contain the internal pressures of the chamber, the breech end of the barrel is usually the largest diameter part of the barrel. Often, the exterior profile of the barrel will include an annular shoulder against which the gas block will abut when in place. The inside diameter of the opening in the gas block closely matches that of the outside diameter of the barrel at the location where the gas block is to be mounted. These interface areas are machined with precision and usually have a clearance of less than 0.005 inches in diameter. The outside diameter of the barrel profile forward of the gas block position can be no greater than that of where the gas block is mounted, in order to allow assembly. 
     After the gas block is mounted, a muzzle device may be attached to the threaded muzzle end of the barrel. When the rotational position of the muzzle device, such as a brake or compensator, must be indexed to the barrel (to coincide with a predetermined “up” direction), a crush washer or spacing shims are often used in the attachment of the muzzle device. In order to comply with arbitrary total barrel length requirements in some jurisdictions, the muzzle device may be permanently affixed to the barrel, such as by drilling a hole through the threaded engagement, inserting a pin that will prevent subsequent rotation, and welding the pin in place to prevent removal. Known muzzle devices have an outside diameter greater than the bore diameter of known gas blocks. Thus, once installed, a gas block cannot be removed from the barrel without removing the muzzle device. If the muzzle device is permanently affixed to the barrel, removal requires cutting (and, typically, destroying) either the gas block or muzzle device. If the gas block is cut for removal and the muzzle device remains in place, the gas block can then be replaced only with a clamp-on or multi-part gas block body, which is heaver and typically creates a larger cross-sectional profile than one-piece gas blocks. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method of removing a gas block without removing the muzzle device. The apparatus provides a combination of a barrel, gas block, and muzzle device having an outside diameter no greater than the bore of the gas block or outside diameter of the barrel at the point where the gas block is mounted. The method provides selection of these parts and allows the gas block to be slid off the barrel, over the muzzle end, and over the low profile muzzle device and re-installation of a gas block over the muzzle device, without removal of the muzzle device. 
     Accordingly, it has been one objective of the invention to provide a combined barrel, gas block and muzzle end apparatus of a firearm wherein the gas block can be removed from or assembled to the barrel over the muzzle end apparatus. 
     A further objective of the invention has been to provide a method by which a gas block of a firearm is removed from or assembled to a barrel of a firearm over a muzzle end device secured to the barrel. 
     A further objective of the invention has been to provide a method of assembling a gas block to, or removing a gas block from, the barrel of a firearm and over a muzzle end device affixed to the barrel. 
     A yet further objective of the invention has been to provide a method of removal from, or assembling to, a barrel of a firearm an integral gas block without removal of a muzzle end device affixed to the barrel and without cutting or destruction of the gas block. 
     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 DRAWINGS 
       Like reference numerals are used to indicate like parts throughout the various figures of the drawings, wherein: 
         FIG. 1  is a side elevation view of a barrel for a gas operated semi-automatic firearm showing a gas block and muzzle device installed on the barrel thereof according to the prior art; 
         FIG. 2  is a longitudinal sectional view of the prior art apparatus of  FIG. 1 ; 
         FIG. 3  is a side elevation view of a barrel, gas block, and flash hider device assembly for a gas operated semi-automatic firearm according to one embodiment of the present invention; 
         FIG. 4  is a longitudinal sectional view of the apparatus of  FIG. 3 ; 
         FIG. 5  is a side elevation view of a similar but an alternate embodiment of the present invention in which the muzzle device is a muzzle brake; 
         FIG. 6  is a longitudinal sectional view of the apparatus of  FIG. 5 ; 
         FIG. 7  is a side elevation view of one embodiment of the invention illustrating a method of removing a gas block from the firearm barrel without removal of the muzzle device according to one embodiment of the present invention; and 
         FIG. 8  is a longitudinal sectional view of the apparatus of  FIG. 7  illustrating movement of the gas block for removal or assembly over a muzzle device according to an apparatus combination and method of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawing figures, particular embodiments of the invention and their detailed construction and operation are described. 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 are not shown or not described in detail to avoid obscuring aspects of the embodiments. 
     Referring first to  FIGS. 1 and 2 , therein is shown a prior art assembly of a firearm barrel  10 , gas block  12 , and muzzle device  14 . The rotational position of the muzzle device  14  relative to the barrel  10  may be fixed by use of shims or a crush washer  16 , as shown. The illustrated barrel  10  is that of a common profile used for AR15-pattern firearms. It includes an enlarged annular shoulder  18  against which the gas block  12  may be positioned. In this position, an internal gas passageway  20  in the gas block  12  is aligned with a gas port  22  in the barrel  10  that communicates gas flow from the axial bore  24  of the barrel  10 . 
     The portion  26  of the barrel  10  where the gas block  12  is mounted will typically have an outside diameter of 0.625 inches on lightweight barrel profiles and 0.750 inches on medium or heavier weight barrel profiles, with the integral barrel-receiving bore of gas block  12  of similar dimension but allowing a fit of block  12  over barrel portion  26 . A muzzle device  14 , such as the common A 2  flash hider illustrated, typically has an outside diameter in excess of 0.850 inches. 
       FIGS. 3 and 4  show assemblies of a barrel  10 , gas block  12 , and muzzle device in the form of a flash hider  28  according to one embodiment of the present invention.  FIGS. 5 and 6  show an alternate embodiment in which the muzzle device is a muzzle brake  30  fixed in place with a pin  32  permanently locking the threaded connection. In these illustrated embodiments, the portion  26  of the barrel  10  where the gas block  12  is mounted may be 0.625 inches in diameter and the outside profile of the flash hider  28  or muzzle brake  30  is at or less than this diameter, such as 0.620 inches. Accordingly, this apparatus combination allows removal of the gas block  12 , and reassembly thereof, over the muzzle device and barrel without removal of the muzzle device  28 ,  30 . 
     Preferably, the outer diameter of barrel portion  26  and the inner diameter of gas block  12  are both slightly larger than the maximum outer diameter of any portion of any muzzle end device. While these relationships could be of equal diameter some slight tolerance between them facilitates removal and assembly of a gas block  12  over the muzzle end device and the barrel portion  26 . Said in a another way, the maximum outside diameter of the muzzle end device is never greater than the outside diameter of the barrel portion. 
     In any event, it will be appreciated that the relationship of the outer diameter of barrel portion  26  and the maximum outside diameter of the muzzle end device  28 ,  30  (including any crush washer  16 ) is significant as it is desired that the inner diameter of gas block  12  be closely fitted to the outer diameter of barrel portion  26 , but not with an inner diameter less than the outer diameter barrel portion  26  (or of the muzzle end device). With such desired relationships, and according to the invention, the outer diameter of any muzzle device  28 ,  30 , and of any crush washer  16  or similar element, is no greater than the outer diameter of barrel portion  26 , and preferably slightly less. More particularly, the term “slightly less” means, herein, at least a few thousandths of an inch thus insuring an easy passage of gas block  12  over devices  28 ,  30 . This relationship insures that the inner diameter of gas block  12  is thus always slightly in excess of the outer diameter of any muzzle end device  28 ,  30 , or washer  16 , according to the invention. Thus, in a combination of barrel, gas block and muzzle end device according to the invention, the gas block can be slid over the muzzle end device and any related apparatus such as a crush washer  16 . 
     Referring now in particular to  FIGS. 7 and 8 , therein are illustrated methods of assembly and/or disassembly according to the present invention. As shown, a muzzle device, such as a flash hider  28 , may be installed on the muzzle end of a barrel  10  either before or after a gas block  12  is installed. Likewise, a gas block  12  may be installed on a barrel  10  either before or after a muzzle device, such as a flash hider  28 , is installed. 
     Removal of the gas block  12  may be accomplished by disconnecting any other means (such as cross pins or set screws, not shown) for attaching the gas block  12  to the barrel  10  and sliding the gas block  12  toward the muzzle end of the barrel  10 , as represented by arrow  34 . As shown in  FIG. 8 , the gas block  12  is passed over the muzzle end device, such as flash hider  28 , and off the barrel and muzzle end device without prior removal of the muzzle device when its outer profile or diameter is selected to be no greater than that of the portion  26  of the barrel  10  where the gas block  12  would be mounted. Accordingly, a gas block  12  may be removed by sliding it (arrow  36 ) over the muzzle device (hider  28 ) even if the muzzle device is permanently pinned (shown at  32 ) to the barrel  10 . Likewise, the same or a different gas block  12  according to the invention, may be installed by sliding it over the muzzle device (as represented by arrow  38 ) and fixing it in place on the barrel  10  against the annular shoulder  18  in alignment with the gas port  22  according to a method of the present invention. Cutting of either the gas block  12  or muzzle device  28 ,  30 , or its removal is unnecessary for removal of block  12 . Likewise, a new gas block  12  can be installed on the barrel and over the muzzle device  28 ,  30  without the use of a two-part or clamp-on gas block, which increases weight and/or profile of the gas block. 
     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, defined by the following claim or claims.