Patent Publication Number: US-9851167-B2

Title: Switch barrel recoil lug

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/308,760 filed Mar. 15, 2016, the entire contents thereof are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to firearms, in particular bolt action rifles having interchangeable barrels, and more particularly to a recoil lug designed to allow the user of the firearm to change barrels under field conditions with repeatable accuracy and a minimum number of tools. 
     BACKGROUND OF THE INVENTION 
     Depending upon the type of game being hunted or the conditions in which a hunter is pursuing the game, different caliber ammunition can be required. Consequently to accommodate different caliber ammunition, a hunter must carry a number of different firearms which can be inconvenient. Consequently rifles have been developed with a single action and stock that will accept a variety of different barrels thereby eliminating the need to carry separate firearms. In these instances, interchangeable rifle barrels of different calibers can be conveniently carried by the hunter. The interchangeable rifle barrels have different caliber bores as desired. 
     As can be appreciated, changing barrels on a firearm must be done precisely and accurately to avoid issues with firearm performance. Prior firearm designs included complicated constructions to provide accuracy and compatibility or the need for complicated or specialized tools to exchange the barrels. One can appreciate that it would be desirable for a hunter in the field to have a rifle design which can provide repeatable accuracy for changing the barrel and can be done with a minimum number of tools. Consequently a need exists for a firearm having a switch barrel recoil lug which can provide the user to change barrels under field conditions with repeatable accuracy and a minimum number of tools. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a switch barrel recoil lug for a bolt action rifle having interchangeable barrels which allows the user to change barrels under field conditions with repeatable accuracy and a minimum number of tools. The switch barrel recoil lug of the present invention is positioned between a face of a rifle action and a torque shoulder of the rifle barrel and replaces a standard recoil lug and therefore acts as both a recoil lug and a barrel clamping system. The switch barrel recoil lug of the present invention can include various embodiments, and for example, includes a body portion having a rifle barrel shank bore and a stock flange extending below the rifle action. The body portion is solid having front and back surfaces machined parallel to each other. The stock flange allows the lug to be properly fitted to the rifle stock for optimum accuracy and prevents flexing of the lug under recoil stress when the rifle is fired. 
     The switch barrel recoil lug has a clamping system which can include a split flange on a top portion of the lug to allow expansion and contraction of the lug around the barrel shank. A single screw extends through a threaded bore in the split top flange on an axis perpendicular to the barrel axis. The barrel shank bore through the recoil lug, through which the barrel passes, is larger in diameter than the diameter of the barrel shank so that the shank can pass through the lug freely when the clamp screw is loose. 
     The barrel of the rifle is threaded into the rifle action on one end and hand tightened against the face of the recoil lug. Once the barrel is hand tight, the clamp screw is tightened which contracts the sides of the lug against the barrel shank. The clamping force of the lug holds the barrel securely in place and prevents loosening of the barrel from the rifle action. In one configuration, the barrel shank bore hole in the recoil lug can be machined flat or in another embodiment, is machined with a tapered surface that increases in diameter toward the front face of the lug. In this embodiment, the barrel shank is also machined with a matching tapered surface. The tapered bore surface exerts a multidirectional force on the barrel shank when the clamp screws are tightened, forcing the external threads on the barrel shank into more positive contact with the internal threads of the rifle action. The tapered surface also helps with an alignment of the barrel to the rifle action when the recoil lug is clamped thereby providing an increase in repeatability of point of impact when the rifle is fired. 
     The recoil lug is aligned to the rifle action by the use of index pins or other alignment fasteners. These and other aspects of the present invention will be more clearly understood by reference to the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front view of a switch barrel recoil lug of the present invention; 
         FIG. 1B  is a front view of an alternative embodiment switch barrel recoil lug of the present invention; 
         FIG. 2  is perspective view of the switch barrel recoil lug of  FIG. 1A  installed between a rifle action and rifle barrel; 
         FIG. 3  is an end perspective view of the switch barrel recoil lug of  FIG. 1A  installed on the rifle action and in the stock of the rifle with the barrel removed; and 
         FIG. 4  is an exploded perspective view of the switch barrel recoil lug of  FIG. 3  illustrating the tapered rifle barrel shank bore. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1A and 2-4 , the present invention is directed to a switch barrel recoil lug  10  for use between a rifle action  12  and a barrel  14  of a bolt action rifle. The recoil lug allows for the ability to switch barrels under field conditions with repeatable accuracy and a minimum number of tools. The recoil lug is positioned between a face  16  of the rifle action and a torque shoulder  18  of the rifle barrel. The switch barrel recoil lug replaces a standard recoil lug and acts as both a recoil lug and a barrel clamping system. The switch barrel recoil lug has a barrel face  20  and a rifle action face  22  that are parallel to each other. The switch barrel recoil lug has a split top flange  24  and a lower rifle stock flange  26 . The lower stock flange protrudes below the rifle action and fits within a groove  28  formed in the stock  30 . The stock flange  26  provides for proper fitting to the rifle stock for optimum accuracy and prevents flexing of the recoil lug under recoil stress when the rifle is fired. 
     In the embodiment illustrated in  FIG. 1A  the top flange  24  is machined with a split section  32  extending therethrough to allow expansion and contraction of the recoil lug around the barrel shank  34 . The top flange has a threaded bore  36  extending on either side of the split  32  for receipt of a threaded bolt  38 . The bolt extends through the threaded bore on an axis perpendicular to the barrel axis. The recoil lug has a barrel shank bore hole  40  extending therethrough, through which the barrel shank  34  passes and is machined slightly larger than the diameter of the barrel shank so that the shank can pass through freely when the clamp bolt  38  is loose. The end  42  of the barrel is threaded for engagement in the threaded end  44  of the rifle action. As indicated, the barrel shank bore hole of the recoil lug has a larger diameter than the barrel shank allowing the barrel to be threaded into the rifle action. The threaded end of the barrel is threaded into the threaded end of the rifle action and hand tightened against the barrel face of the recoil lug thereby contacting the rifle action face of the recoil lug against the end face of the rifle action. Once the barrel is hand tightened, the clamp bolt is also tightened which contracts the barrel shank bore against the barrel shank. The clamping force of the recoil lug holds the barrel securely in place and prevents loosening of the barrel from the rifle action. 
     As shown in  FIG. 1B , an alternative embodiment switch barrel recoil lug  46  is illustrated. In this embodiment, the recoil lug is machined as a two piece component having an upper portion  48  and a lower portion  50 . The lower portion  50  includes a stock flange  52  for similarly fitting within groove  28  of the stock. Recoil lug  46  has a barrel shank bore hole  54  positioned therein. Threaded holes  56  and  58  are positioned on either side of the barrel bore hole for receipt of clamp bolts  60  and  62  extending through threaded holes  64  and  66  in top portion  48 . Top portion  48  moves freely in the vertical direction when the clamp bolts are loose. With the clamp bolts loose, the barrel can be inserted through the barrel shank bore hole into the rifle action and hand tightened against the barrel face  68  of the recoil lug. Clamp bolt  60  and  62  are then tightened which contracts the top section of the recoil lug against the barrel shank  34 . The clamping force of the recoil lug holds the barrel securely in place and prevents loosening of the barrel from the rifle action. 
     As shown in  FIG. 3  the barrel shank bore hole in the recoil lug through which the barrel shank passes can be flat or with a tapered surface  70  as shown in  FIG. 4 . The tapered surface  70  increases in diameter toward the barrel side surface of the recoil lug. In this configuration barrel shank  34  is also machined with a matching tapered surface. Tapered bore surface  70  exerts a multidirectional force on the barrel shank when the recoil lug is tightened, forcing the external threads on the barrel shank into more positive contact with the internal threads of the rifle action. The tapered surface also helps with alignment of the barrel within the rifle action when clamped providing an increase in repeatability of point of impact when the rifle is fired. 
     The switch barrel recoil lug can be aligned to the rifle action  12  by a steel index pin  72  which is press fit into the end  16  of the rifle action. Index pin  72  is received within an index hole  74  extending into the rifle action face  22  of the recoil lug. Although a single index pin positioned at six o&#39;clock as illustrated in the drawings, it is to be understood that multiple pins separated from one another could be incorporated. The index pin serves both to align the lug to the barrel tenon threads of the rifle action, and also to prevent lateral movement of the lug during tightening or loosening of the rifle barrel. As previously indicated, forward movement of the lug is prevented by precisely fitting the stock flange to the rifle stock. Once the recoil lug has been installed onto the rifle action and the barrel is tightened in place the rifle action and lug are bedded into the stock with a bedding compound such as Devcon, Acra-Glas or Marine Tex. Once properly fitted to the rifle action and stock, the clamp portion of the recoil lug can be operated properly with no lateral or forward movement of the recoil lug. 
       FIG. 4  illustrates an alternative method to secure the recoil lug to the rifle action wherein threaded holes  76  can be machined through the recoil lug and also threaded holes  76  can be machined into the end face of the rifle action. The recoil lug could then be attached by means of threaded screws with countersunk or counter bored heads so that they do not protrude into the contact area for the barrel shank torque shoulder. Screws  78  would need to be coated with a thread locking adhesive during installation to guard against loosening from vibration over time. Given the minimal area between the index holes and the barrel shank bore hole for the barrel shank, once the screws are installed the portion of the screw heads that may protrude into the barrel bore hole would be machined flush with the inside diameter of the barrel shank bore hole. As shown in  FIG. 2 , further alternatively, the switch barrel recoil lug could be welded to the rifle action along a bottom seam  80 . This could be accomplished by TiG welding with an appropriate filler rod. For instances of welding, the rifle stock would be inletted in the corresponding area for clearance of the seam so that the rifle action face of the recoil lug is in full contact with the stock bearing surface. 
     Although the present invention has been described and illustrated with multiple embodiments thereof, it is to be understood that other modifications could be made therein which are within the full intended scope of the invention as hereinafter claimed.