Abstract:
Disclosed herein is a retrofit device to be attached to shotguns and other long barrel firearms, such as some rifles, to allow adaptation of the firearm for attachment to a detachable box magazine.

Description:
RELATED APPLICATIONS 
     This application claims priority benefit of U.S. Ser. No. 61/292,372, filed Jan. 5, 2010. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     This disclosure relates generally to a retrofit device to be attached to shotguns and other long barrel firearms, such as some rifles, to allow adaptation of the firearm for attachment to a detachable box magazine. Many prior art firearms, such as that disclosed in U.S. Pat. No. 2,081,235, were specifically formed to allow insertion of a removable box magazine by way of engaging the forward portion of the box magazine generally, as indicated at  42 , and then pivoting the box magazine around this point until a rearward engagement latch, such as that shown at  48 , would maintain engagement of the box magazine within the firearm. Additionally, some firearms were formed with non-removable magazines, wherein the magazine would be attached to the firearm, and once attached, shells would be fed into the magazine normally through the firearm breech or a similar portion of the firearm. One such non-removable magazine is the tube magazine found in many pump-action shotguns. Another example is the fixed box magazines often found in bolt action firearms. Enclosed herein is the disclosure to retrofit these and other styles of firearms with non-removable magazines or no magazines, which allows for linear insertion of a modern-style straight insert box magazine. Such straight insert magazines are well known in current automatic weapons and some semi-automatic weapons, including AAR-15&#39;s, M-16&#39;s and others. 
     SUMMARY OF THE DISCLOSURE 
     Disclosed herein are several embodiments of a retrofit magazine well for a shotgun having a receiver location. The retrofit magazine well comprises a magazine well body and a release lever. The magazine well body comprises an exterior surface, an interior surface configured to removably receive a shotgun shell box magazine, an upper surface configured to engage the receiver location of the shotgun, and a plurality of surfaces defining voids configured to receive fasteners therethough, which engage aligned threaded surfaces within the shotgun adjacent the receiver location of the shotgun. The release lever comprises a user engagement end, a pivotable coupling to the magazine well body, and a magazine engagement end, operatively configured to release or retain the box magazine within the interior surface of the magazine well body. 
     The retrofit magazine well body is comprised of two separate sub portions, which are substantially mirror images of each other. The retrofit magazine may be arranged wherein the user engagement end of the release lever extends rearward beyond the well body. 
     Also disclosed is a method for retrofitting a firearm comprising the steps of providing a magazine well body and a release lever as described, gaining access to the chamber of the firearm, and fixing the magazine well body to the firearm such that the interior surface of the magazine well body is contiguous with the chamber of the firearm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of the retrofit adapter being mounted upon a highly schematic firearm. 
         FIG. 2  is an isometric exploded view of the components of the adapter. 
         FIG. 3  is a plan view of the release latch, in one form. 
         FIG. 4  is a side hidden line view of the release latch, in one form. 
         FIG. 5  is a plan view of an assembled adapter. 
         FIG. 6  is a side hidden line view of the adapter, in one form. 
         FIG. 6  is a side hidden line view of the adapter, in one form. 
         FIG. 7  is a side partial cutaway view of a prior art shotgun. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Looking to  FIG. 1 , the adapter  20  is shown being attached to a highly schematic firearm  22  by way of a plurality of forward fasteners  24  and a plurality of rear fasteners  26 , of which only one can be seen in this view. In one form, the fasteners  24  and  26  are attached through a plurality of clearance holes  28 , and they engage a plurality of threaded holes  30  in the firearm  22 . The adapter  20  generally comprises two separate portions, one being the magazine receiver  32  and the other being a latch  34 , generally comprising a release lever  36  and other components to be disclosed below. The magazine receiver  32  is configured to accept a straight insert, detachable box magazine  38 , which is held in place by way of the latch  34 , as will be discussed later. 
     Looking to  FIG. 2 , an exploded view of the adapter  20  can be seen, wherein the magazine receiver  32  comprises a right side portion  32   a  and a left side portion  32   b , which are substantially mirror images of each other and may be attached by way of fasteners  40  or other means. It may be desired to have a clearance hole  42  within the left side portion  32   b  and possibly a recess  44  to allow the head  46  of the fastener  40  to reside therein, such that the head  46  of the fastener  40  does not extend outward beyond the left outer surface  48 . Furthermore, a threaded hole  50  may be provided in the right side portion  32   a  to receive the threaded portion  52  of the fasteners  40 . Additionally, each of these portions may comprise a tapered cutout, engagement or receiving surface  54 , which is configured to allow easy placement of the box magazine  38  within the interior portion  56  of the adapter  20 . These receiving surfaces  54  will be described in more detail with regards to  FIG. 6 . 
     The latch  34 , in one form, can also be quite readily understood by looking at  FIG. 2 . The latch  34  in this embodiment comprises the release lever  36 , which is pivotably attached to the magazine receiver  32  by way of a pivot pin  56 , which is fitted through a matching void  58  in the adapter  20  and a matching a void  60  in an extension  62  of the release lever  36 . The extension  62  generally fits within a void  64  provided in the receiver  32 , wherein the void  64  is sized and configured to allow rotation of the release lever  36  about the pivot pin  56 . As shown, the release lever  36  comprises a forward surface  66 , which is normally parallel to and in contact with the right outer surface  68  of the adapter  20 , such that a tapered extension  70  extends through a void  72  to the interior portion of the adaptor  20 . The tapered extension  70  is operatively configured to engage a void in a modern, straight insert, box magazine, such as is well known in the art. A spring  74  or similar apparatus may be configured to provide elastic force to maintain the release lever  36  in this position until a user exerts force upon the rearward extension  76  toward the right outer surface  68 , which will pivot the release lever  36  about the pivot pin  56 , thus removing the tapered extension  70  from the interior portion of the adapter  20 , and thus releasing the box magazine  38  by way of gravity, or in some cases by elastic means. One example of a magazine utilizing this type of attachment is described in U.S. Pat. No. 4,139,959, incorporated herein by reference, which includes an opening generally at  18  of  FIG. 1  for connection to the tapered extension  70 , as described above. This is but one example of such a cartridge, and other arrangements are well known in the art. 
     While the latch is shown as extending from and being activated from the right side of the firearm, the latch could just as easily extend from the left side, or alternately could be configured to extend from both sides, with special provisions made for this arrangement. 
     Looking to  FIG. 3 , the release lever  36  is shown in plan view, including a recess  78  for the spring  74 , as well as the void  60  for passage of the pivot pin  56 . It can also be seen how in one form the release lever  36  is bent at points  80  and  82  to allow the user to easily engage the rearward extension  76  and to allow the release lever  36  to pivot about the void  60 . These elements are also shown in the side view of  FIG. 4 . 
     The release lever  36  and adapter  20  are also shown in an assembled plan view in  FIG. 5 . Additionally,  FIG. 6  shows a side cutaway view of these components. Additionally, in  FIG. 6 , it can be seen how the receiving surfaces  54   a  and  54   b  allow for easy positioning of the box magazine into the opening  84  of the adapter  20 , as the adapter opening  84  is substantially larger than at the upper portion  86  where the guide surfaces  88   a  and  88   b  are substantially parallel and only slightly larger than the magazine  38 , such that once the magazine passes the border  90  between the tapered portion  54  and the parallel portion  88 , the magazine  38  will be in the correct alignment relative to the chamber of the firearm  22 . 
     In one form, to mount the adapter  20  to a firearm  22 , such as a shotgun, the “elevator”  92  of a tube-fed shotgun  94  would be removed and the adapter  20  would be attached thereto so as to allow the firearm to utilize a straight-insert, detachable box magazine  38 . 
     While the present invention is illustrated by description of several embodiments and while the illustrative embodiments are described in detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the scope of the appended claims will readily appear to those sufficed in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants&#39; general concept.