Abstract:
The invention comprises a device and various optional modifications to the lower receiver of a semiautomatic firearm whereby the firearm is at least semi-permanently rendered incapable of quickly removing and replacing a cartridge magazine. The device comprises a means to mechanically retain the magazine in the lower receiver of the firearm such that special tools and at least several minutes are required to remove and replace the magazine. The optional modifications comprise elimination of certain standard machined features which accept and allow the use of a magazine catch, magazine catch spring and magazine catch button; introduction of a hole or slot through the sidewall of the magazine well to accommodate a magazine retention fitting which holds the magazine in place; and the interruption of the lower portion of a clearance slot in the magazine well to prevent installation of a magazine from the bottom of the receiver. The various embodiments of this invention allow the user or manufacturer to control the time required to remove and replace a magazine over a range of approximately 3-20 minutes and the level of special tooling needed to accomplish the exchange.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Modern Sporting Rifle Design Modifications for Enhanced Public Safety—Disclosure #2; Provisional Patent Application Number 61/951,052; Filing Date Mar. 11, 2014 
     Modern Sporting Rifle Design Modifications for Enhanced Public Safety—Disclosure #3; Provisional Patent Application Number 61/973,981; Filing Date Apr. 2, 2014 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
     Not applicable 
     TECHNICAL FIELD 
     The invention relates generally to semi-automatic firearms and more specifically to a means for semi-permanently retaining the magazine of a semi-automatic firearm, rendering in at least temporarily incapable of accepting a detachable magazine. 
     BACKGROUND OF THE INVENTION 
     Modern Sporting Rifles (MSR) based on the AR-10 and AR-15 platforms, firearms originally designed by Armalite, with calibers ranging from 0.22 to 0.308, are among the most popular firearms sold in the world today. These AR-platform MSRs, however, have come under increased public scrutiny recently as the result of several high profile shooting incidents. State legislatures in a number of states, most notably Connecticut and New York, have enacted tough new laws to curb the use of these rifles and limit the perceived danger to the public. These restrictions have generally focused on the possession and use of high capacity magazines and features such as pistol grips and flash suppressors that are closely associated with guns often referred to as assault weapons. Unfortunately, these provisions do little to physically prevent the use of high capacity magazines or, more importantly, modify the speed with which a shooter can swap out one low capacity magazine for another and resume firing. Thus, the opportunity for Law Enforcement or potential victims to respond, during periods when a deranged shooter is trying to reload and resume shooting, has not been substantially affected. Moreover, efforts to physically limit the number of rounds that can be loaded into a firearm have been generally ineffective. Yes, laws regulating the possession and use of high capacity magazines (more than 10 rounds) have been passed, but higher capacity magazines are easily obtainable and nothing physically prevents their use in standard MSRs. 
     Given that the public interest in owning MSRs is unlikely to diminish and the ready availability and ease of use of high capacity magazines, while now illegal in some states, has not really changed, another approach to limiting the lethality and negative impact on public health is needed. 
     The standard MSR is manufactured and sold in a configuration allowing it to accept a detachable magazine that can be removed and replaced in seconds. This process does not require disassembly of the action of the firearm. 
     What is needed are new designs which physically limit the use of high capacity magazines and/or slow the reloading process. Such design modifications could significantly enhance the public safety without unreasonably interfering with Second Amendment rights to bear arms. This combination of design modifications would create longer interruptions in the use of one of these weapons during a shooting spree and provide an opportunity for potential victims to escape or time for others to rush in and overwhelm the shooter. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a means for converting a semi-automatic firearm from a configuration capable of readily and quickly accepting or exchanging a detachable magazine into a configuration which semi-permanently fixes the magazine and thereby temporarily renders the firearm incapable of accepting or exchanging a detachable magazine. 
     For the purpose of this summary and later descriptions, the terms “semi-permanent” or “semi-permanently” and “temporary” mean a configuration or state of being that requires special tools and/or disassembly of the action of the firearm and a period of time on the order of approximately 3-20 minutes, or more, to remove and exchange a magazine or modify the configuration to one capable of readily accepting a detachable magazine. 
     It is another purpose of the invention to optionally make it more difficult to reconfigure the firearm back to a standard configuration, i.e., to easily replace the standard magazine catch, magazine catch spring and magazine catch button so as to easily defeat the fixed magazine nature of the firearm “on demand.” 
     It is another object of the invention to optionally modify the way a magazine is inserted into the receiver of the firearm such that certain (curved) high capacity magazines cannot be used. 
     It is another object of the invention to require that the magazine can only be removed and replaced when the firearm is in a disassembled state. 
     It is another object of the invention to optionally require that at least one other component (besides the magazine retention components) of the lower receiver be removed prior to the removal of the magazine. 
     It is another object of the invention that a magazine can only be loaded into the firearm when the magazine is empty. 
     It is another object of the invention to prevent the use of reloading aids such as stripper clips that would greatly speed up the loading of cartridges into the magazine. 
     It is another object of the invention to create a parts kit that can be used to quickly accomplish the conversion of the firearm to a semi-permanently fixed magazine configuration. 
     It is a purpose of the invention to significantly increase the amount of time required to reload a semi-automatic firearm. 
     It is another purpose of the invention to provide a strong visual cue to any observer when the firearm is out-of-service and being reloaded. 
     A standard semi-automatic AR-platform firearm contains a magazine catch assembly housed within various machined recesses within the lower receiver. A standard magazine catch assembly is comprised of a magazine catch, a magazine catch spring, and a magazine release button. The magazine catch consists of two ends which occur at a substantially right angle. One end is provided with screw threads. The other end is a substantially flat member with a small protrusion on one side distal to the threaded screw portion. The magazine catch assembly is installed into a recess in the lower receiver by first inserting the threaded end of the magazine catch into a through-hole in the receiver. The magazine catch spring is then placed over the threaded screw end of the magazine catch from the opposite side of the receiver. And finally, the magazine catch button is pushed into its recess, on top of the spring, and the threaded screw end of the magazine catch is threaded into the magazine catch button. When fully assembled, the flat end of the magazine catch, with its small protrusion, is nested into a slot which passes through the side wall of the magazine well. The small protrusion on this flat extends into the magazine well and is available to engage with a feature on the side wall of the magazine to hold it in place. Once a magazine is inserted into the magazine well, and the protrusion on the magazine catch slides into the recess in the magazine, the magazine is held in place until the user releases the magazine by pushing the magazine release button. When the magazine release button is depressed, the magazine catch is lifted from the recess in the magazine wall and the magazine freely slides out of the magazine well. 
     A standard lower receiver has a magazine well with a uniform profile in cross-section from top to bottom of the well, typically achieved by passing a broaching tool through the entire length of the magazine well. The standard profile hence incorporates a full-length clearance slot along the side to allow easy passage of a raised portion on the side of the magazine which is designed to interact with the magazine catch. 
     The present invention is an alternative design for the lower receiver which can be substituted for the standard lower receiver of an AR-platform firearm. The invention maintains every current function of the standard lower receiver except the ability to quickly load and unload magazines into the magazine well. In its geometry, the alternative design is identical in all aspects to the standard lower receiver except that it preferably omits the slot, hole and machined recess which would normally accommodate the magazine catch, spring and magazine release button hardware respectively as described above. 
     In accordance with one embodiment of the present invention, the magazine is semi-permanently attached to the lower receiver using a retention screw and a retention fitting. To accommodate the fitting, the lower receiver is manufactured with a hole through the side wall of the magazine well in the same general location as the slot in the standard version. The retention fitting is held in place by a retention screw and loosely engages the magazine, passing through the recess in the magazine from the inside to the outside, and bearing on its inside surface of the magazine. In another embodiment of the present invention, the retention screw is replaced by a rivet to more permanently attach the magazine to the lower receiver. In a third embodiment of the invention, the fitting does not have threads or a hole to accommodate a screw or rivet, but is actually designed to function itself like a special rivet, having an elongated cylindrical section whose end can be deformed to prevent being withdrawn once it is fully installed. In accordance with all three of these embodiments of the invention, the fitting can only be installed when the magazine is empty and the magazine follower has been retracted to allow access to the recess in the side of the magazine from the inside surface. Retraction of the magazine follower can occur either by using special tools to compress the magazine follower spring and hold the magazine follower in the retracted position or by removing the bottom plate of the magazine, removing the follower spring, and lowering the magazine follower once all spring pressure has been removed. 
     In accordance with another embodiment of the present invention, the magazine well is modified to allow magazines to be inserted only from the top of the lower receiver. This is accomplished by interrupting the full-length clearance slot along the side by one of two ways. Option one is to avoid removing the material at the bottom of the slot during magazine well forming. Option two is to fill the bottom of the slot after it is formed. The first option can be achieved, for example, by broaching or using a wire edm process to form the well without the required clearance slot and then secondarily machining away the upper portion of the slot. The second option can be achieved by broaching or using a wire edm process to form the well with the a full-length clearance slot and then filling the bottom of the slot with a metal plug or other insert generally conforming to the slot geometry while not interfering with travel of the magazine follower or follower spring. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side view of a firearm typical of a standard original equipment manufacturer (OEM) product capable of accepting a detachable magazine. 
         FIG. 2  is an exploded side view of the same firearm shown in  FIG. 1  broken down into major component groups. 
         FIG. 3  is a side view of the same firearm shown in  FIG. 1  with the upper receiver assembly rotated forward on the front pivot pin. 
         FIG. 4  is an exploded view of a standard lower receiver showing only the components associated with retaining and releasing a detachable magazine. 
         FIG. 5  is a perspective view of the top and left sides of an alternative lower receiver embodying the features of the present invention for semi-permanently fixing a magazine. 
         FIG. 6  is a perspective view of the top and right sides of an alternative lower receiver embodying the features of the present invention for semi-permanently fixing a magazine. 
         FIG. 7  is a perspective view of the top and right sides of a standard lower receiver designed for retaining and releasing a detachable magazine. 
         FIG. 8  is an exploded perspective view of the top and left sides of an alternative lower receiver assembly embodying the features of the present invention for semi-permanently fixing a magazine including the magazine and components involved in semi-permanently retaining the magazine. 
         FIG. 9  is a perspective view with the various components shown in  FIG. 8  collapsed into their normal position. 
         FIG. 10  is a close-up of the view shown in  FIG. 9 , but also showing some details on the top of the magazine that were not clearly visible in  FIG. 9 . 
         FIG. 11  is a perspective view of an alternative lower receiver assembly with the magazine follower retracted so the magazine retention fitting is visible. 
         FIG. 12  is a perspective view showing details of the magazine well geometry for an alternative lower receiver of the present invention with an uninterrupted clearance slot. 
         FIG. 13  is a perspective view showing details of the magazine well for the alternative lower receiver with an interrupted clearance slot. 
         FIG. 14  is a perspective view of one embodiment of the retention screw used in the present invention. 
         FIG. 15  is a perspective view of one embodiment of the retention fitting used in the present invention. 
         FIG. 16  is a perspective view of a typical magazine that has been slightly modified (by the addition of a drilled hole in the magazine follower) for easier installation in the lower receiver of the present invention. 
         FIG. 17  is a perspective view of one embodiment of an alternative retention fitting that could be used to retain a magazine in a standard lower receiver. 
         FIG. 18  is an exploded view of a magazine and follower along with special tooling that can be used to retract the follower for easier installation of the magazine retention fitting. 
         FIG. 19  is an enlarged sectional view of a magazine and follower showing how the special tooling described for  FIG. 18  engages the follower. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Since the basic firearm is of a well-known type, only those parts of the firearm essential to an understanding of the invention will be described in detail. Although the present invention will be described with reference to the exemplary embodiments shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms or embodiments. In addition, any suitable size, shape or type of elements or materials could be used. 
     Referring to  FIGS. 1-3  the standard firearm  100 , capable of accepting a detachable magazine  200 , is comprised of an upper receiver assembly  20  and a standard lower receiver assembly  30 . As shown in  FIG. 2  the standard lower receiver assembly  30  comprises partially a stock assembly  80  and a pistol grip  90 . Note: subsequent drawings described for this invention will show the standard lower receiver assembly  30  exclusive of the stock assembly  80  or the pistol grip  90  for clarity. As shown in  FIG. 3  the upper receiver assembly  20  and the standard lower receiver assembly  30  can scissor open when the rear takedown pin  50  is removed, allowing the upper receiver assembly  20  to be pivoted at the point of the pivot pin  60 .  FIGS. 1-3  show the standard configuration of the firearm  100 , i.e., one capable of accepting a detachable magazine  200 . 
     Referring to exploded view  FIG. 4  and  FIG. 16 , the standard lower receiver assembly  30  comprises partially a standard lower receiver  35 , a magazine catch  10 , a magazine catch spring  11 , a magazine release button  12 , and a magazine well  31 . When fully assembled, the threads  102  of the magazine catch  10  engage with the threads  125  of the magazine release button  12 . The circular end  103  of the magazine catch  10  passes through hole  104  in the standard lower receiver  35 , then through the magazine catch spring  11  which forcibly biases the magazine catch  10  toward the bottom  106  of slot  13 . When magazine catch  10  is properly aligned, the flat end  105  of the magazine catch  10  aligns with and is nested into slot  13  in the standard lower receiver  35 . When a magazine  200  is installed in the magazine well  31 , the protrusion  101  on the flat end  105  of the magazine catch  10  nests into the opening  202  of the magazine  200  and the edges of the protrusion  101  of the flat end  105  of the magazine catch  10  bears on the edges  203  of opening  202  of magazine  200 , holding it firmly in place within the magazine well  31 . 
     Referring to  FIGS. 4 and 5 , an alternative lower receiver  45  is shown for comparison with the standard lower receiver  35 . This alternative lower receiver  45  is one embodiment of the lower receiver for the present invention. The key difference visible in these two views is the presence of the hole  15  in the alternative lower receiver  45  in lieu of the slot  13  in the standard lower receiver  35 . 
     Referring to  FIGS. 4, 6 and 7 , the key difference visible in  FIGS. 6 and 7  is the absence of the oval recess  122  present in face  123  of the standard lower receiver  35  but not present in face  124  of alternative lower receiver  45 . As should be apparent, the through hole  104  of  FIG. 4 , as well as a recess/counterbore (not shown) for the magazine catch spring  11 , are also omitted in alternative lower receiver  45 . 
     Referring to the exploded view in  FIG. 8  and  FIGS. 14, 15 and 16 , the alternative lower receiver assembly  40  is partially comprised of the alternative lower receiver  45 , a fixed magazine  200 , magazine follower  210 , magazine retention screw  151 , magazine retention fitting  152 , bolt catch  120 , and bolt catch pivot screw  121 . When fully assembled, magazine  200  is positioned inside of the magazine well  41  of the alternative lower receiver  45 . Magazine  200  is primarily held in place by magazine retention fitting  152 . Magazine retention fitting  152  is designed to pass through opening  202  in magazine  200 , from the inside of magazine  200  outward. Once installed, the flat edges  155  of magazine retention fitting  152  bear against the upper and lower surfaces  203  of opening  202 , the flat face  153  of magazine retention fitting  152  bears against the inside wall of magazine  200 , and the cylindrical face  154  of magazine retention fitting  152  is concentrically aligned with and passes through hole  15  of the alternative lower receiver  45 . The length of the cylindrical face  154  is configured to be long enough that the magazine retention fitting does not bear forcibly against the inside wall of magazine  200  once flat face  156  of magazine retention fitting  152  makes contact with the bearing face  159  of magazine retention screw  151 , after the screw threads  158  of magazine retention screw  151  have fully engaged the screw threads  157  of magazine retention fitting  152 . At the same time, the length of the cylindrical face  154  is configured to be short enough that the magazine retention fitting does interfere with the movement of the magazine follower  210  or the follower spring. 
     The method of capturing the magazine retention fitting  152  described above involves use of a magazine retention screw  151 . In  FIG. 14  this screw is illustrated as a button head screw suitable for use with a hexagonal drive wrench. Alternatively, the magazine retention fitting  152 , could be captured using a screw of any other configuration (torx, phillips, slotted), an anti-tamper screw that cannot be easily unscrewed, or even a rivet and washer. These options give the producer of this invention some flexibility in the degree of permanence of fixing the magazine  200  in place. Alternatively, the magazine retention fitting  152  could be fabricated with an elongated cylindrical section  154  and, omitting the through-hole and threads, be configured as a custom-shaped rivet. This custom rivet could be installed as described for the current magazine retention fitting  152  from the inside of the magazine  200  and then have the outside cylindrical face  156  deformed as is typically done with a rivet with the deformation occurring on the outside of the alternative lower receiver  45  once the rivet end has passed through hole  15 . This deformation would most permanently install retention fitting  152  and magazine  200  such that the retention fitting  152  would have to be destroyed to remove magazine  200 . 
     Referring to  FIGS. 9, 10, 12 and 13 , notice that bolt catch  120  overlaps and is pushed up by magazine follower  210  when there are no cartridges in the magazine. Also note that bolt catch  120  will prevent magazine  200  from being removed vertically upward from the alternative lower receiver  45 . When combined with the interrupted clearance slot  42 A embodiment of magazine well  41  as shown in  FIG. 13 , it should be obvious that magazine  200  can only be removed from the alternative lower receiver  45  after first removing both the magazine retention screw  151  and removing the bolt catch  120 . Similarly, it should be obvious that inserting and securing magazine  200  can only be done before the bolt catch  120  is installed into the alternative lower receiver assembly  40 . If, alternatively, the present invention is produced with an uninterrupted clearance slot  42  as shown in  FIG. 12 , the magazine  200  can be inserted from the bottom of magazine well  41  and it is unnecessary to remove bolt catch  120  to accomplish insertion. 
     Referring to  FIGS. 8, 11 and 15 , the position of magazine retention fitting  152  is shown in its installed position in  FIG. 11  inside magazine  200 . Notice that to install magazine retention fitting  152 , the magazine  200  must be empty of any cartridges and the magazine follower  210  must be displaced downward to make access to hole  15  in alternative lower receiver  45  possible. In practice, installation of the magazine retention fitting  152  could be done, but with great difficulty, without special tools. To make this task easier, various special tools to retract and hold magazine follower  210  (against spring pressure from a magazine follower spring—not shown) in its retracted position inside magazine  200  and then load and position magazine retention fitting  152  through opening  202  and hole  15 , prove to be very helpful. Also note in  FIG. 11  that the thickness of the circular section of magazine retention fitting  152  defined by face  153  and its outward opposite face must be thin enough that the magazine follower  210  is not impeded as the magazine follower  210  cycles up and down inside magazine  200  as cartridges are loaded and removed. 
     Referring to  FIGS. 3, 4, 7, 12, 13, 15, 16 and 17 , the clearance slot can be created in two configurations: the interrupted geometry of clearance slot  42 A clearly differs from the constant section properties of clearance slot  42 . It is this interrupted geometry of clearance slot  42 A that creates one embodiment of the present invention as it interferes with the raised boss  201  on magazine  200  and prevents magazine  200  from being loaded into the magazine well  41  from the bottom as is the normal practice for firearms of this general type. This feature also effectively prevents the use of any curved magazine, often referred to as a “banana” magazine, since passing such a curved magazine through the entire magazine well from the top to properly seat the magazine, however it is retained, is not possible. Many, but not all, high capacity magazines have this curved profile and therefore cannot be used with this embodiment of the invention. A second embodiment of the present invention is created if the clearance slot is not interrupted as shown by clearance slot  42 . In this case the magazine  200  can be loaded into the magazine well  41  from the bottom. So long, however, as the magazine  200  is retained semi-permanently using, for example, the method described involving a magazine retention screw  151  and a magazine retention fitting  152  or  152 A, the objective of this invention to semi-permanently fix the magazine  200  is maintained. 
     The interrupted clearance slot  42 A embodiment of this invention can be achieved in two general ways. In one approach to this embodiment, the interrupted clearance slot  42 A is created by preferentially removing material from the upper half of the wall of the magazine well  41  of the alternative lower receiver  45 , by using, for example, an end mill to machine the material away. Other methods such as electronic discharge machining (EDM) or partial broaching might also be used. The specific method is not important—any suitable material removal process is acceptable so long as it results in removal of material over approximately the top half of the slot only. The other approach to this embodiment for creating an interrupted clearance slot  42 A is achieved by adding material to the bottom half of the wall of the alternative lower receiver  45  after a full-depth clearance slot  42  is first created. One likely means of creating this full-depth clearance slot is the broaching method used to manufacture most firearms of this type today. The added material could, for example, be in the form of a flat plug contoured to fit into the clearance slot  42  without interfering with the insertion of a magazine  200  thereafter. This flat plug could be secured in place by a variety of means such as, for example, one or more screws, one or more rivets, an adhesive such as epoxy adhesive, a combination of mechanical and adhesive means, or by even more permanent methods such as vibration or friction welding. The method is not important so long as it effectively prevents a magazine  200  from being inserted from the bottom of the alternative lower receiver  45 . 
     For the present invention, to load cartridges into the firearm and make it operational in a semi-automatic configuration, it is first necessary to install a magazine  200 . This magazine must be empty to be installed so magazine retention fittings  152  or  152 A can be properly located and aligned to engage with hole  15  in the alternative lower receiver  45  or slot  13  in the standard lower receiver  35 . Depending on how far forward the upper receiver assembly  20  can be scissored open, it may be necessary to fully remove the upper receiver assembly  20  for this step. In any case, and at a minimum, the upper and lower receiver assemblies,  20  and  30  or  40 , must be separated at the rear end of the lower receiver by disengaging the takedown pin  50  from its normally seated location. A second necessary step in the installation of this magazine  200 , applicable only for the interrupted clearance slot  42 A embodiment requiring loading of the magazine  200  from the top of the alternative lower receiver  45 , is the removal of the bolt catch  120 , which otherwise blocks access to magazine well  41  of the alternative lower receiver  45 . Once the bolt catch  120  is removed, magazine  200  can be slid into magazine well  41  from the top of the alternative lower receiver  45 . For the uninterrupted clearance slot  42  embodiment, removal of bolt catch  120  is not required and the magazine  200  can be inserted into magazine well  31  or  41  from the bottom of the well. In either case, the next step is preferably using a special tool to retract the magazine follower  210  to make opening  202  accessible and another special tool to easily carry and align magazine retention fitting  152  or  152 A into hole  15  or slot  13  respectively, so magazine retention screw  151  (or another means of fixation) can be engaged into the magazine retention screw  152  or  152 A to affix it in place. Fully tightening a magazine retention screw  151  requires preventing rotation of the magazine retention fitting  152  while the magazine retention screw  151  is fully seated into the magazine retention fitting  152 . This is easily accomplished when the flat faces  155  of the magazine retention fitting  152  are aligned with and pass through the faces  203  of opening  202  of magazine  200 . Once the magazine retention screw  151  and magazine retention fitting  152  are fully seated so surface  159  bears on surface  156 , or the retention fitting is otherwise affixed, the bolt catch  120  and bolt catch pivot screw  121  can be installed (if they were necessarily removed beforehand). This task is also easier, but can be done otherwise, if the magazine follower  210  is retracted. Once the bolt catch  120  is installed, the magazine follower  210  can be released, any special tooling removed, and the magazine is ready to be loaded with cartridges. 
     Cartridge loading of this fixed magazine firearm can only take place with the upper receiver assembly  20  scissored open from the lower receiver assembly  30  or  40 . Assuming normal dimensions and tolerances specified in most designs for the magazine well, the clearances between the magazine well  31  or  41  and the magazine  200  are too small to allow insertion of a device known as a stripper clip guide—a means to facilitate rapidly loading multiple cartridges that have been preloaded into a special clip to quickly fill the magazine  200 . When the magazine has been loaded with as many cartridges as the shooter wishes to load, up to its maximum capacity, the upper receiver assembly  20  is rotated back into its normal operational configuration and the takedown pin  50  is reinstalled. 
     For this invention, it is only envisioned that the magazine  200  would be removed from the alternative lower receiver  45  to facilitate cleaning or to replace a magazine that has become excessively worn or damaged. The process of removal and replacement of a magazine  200  is preferably done in an area where sufficient lighting and the special tools noted are available and where small components can be easily handled without risk of getting lost. In practice, while it may be done faster with a highly experienced user, the time to remove and replace a magazine  200 , given the embodiment of alternative lower receiver  45  and an interrupted clearance slot  42 A, is typically in the range of 3-5 minutes. 
     Since removal and replacement of the magazine  200  could occur multiple times over the life of a firearm, and since removal and replacement of the magazine  200  requires removal and replacement of the bolt catch  120  for the embodiment incorporating the interrupted clearance slot  42 A, the means for securing the bolt catch  120  for this embodiment has been described as installing a bolt catch pivot screw  121 . Use of this bolt catch pivot screw  121  is in lieu of using a more permanent spring pin as might be more common for the uninterrupted clearance slot  42  embodiment where magazine  200  can be loaded from the bottom of the magazine well  31  or  41 . Spring pins, by their nature, rely on an interference fit between the pin and the hole(s) it is inserted into, said interference being accommodated by the ability of the spring pin to slightly flex diametrically. This approach, using a spring pin, would be problematic if periodic removal of the bolt catch  120  was needed because frequent removal and replacement of this spring pin, necessary for removing and replacing the bolt catch  120 , would cause wear and possible other damage to the lower receiver as it is forced in an out of the mating holes used to position the bolt catch  120 . 
     Referring to  FIGS. 11, 16, 18 and 19 , the small hole  211  in magazine follower  210  is a modification intended to make the retraction of the follower easier. One means of retracting magazine follower  210  is through the use of special tooling comprising a rod  300  (typical of the rods used for cleaning the inside surface of a rifled barrel) with male threads on one end and female threads on the other, a retraction spacer  301 , two flat washers  302 , a machine screw  303  and a nut  304 . Using this tooling, the rod  300  is passed through a hole in the bottom of the magazine  200  and then through hole  211  in magazine follower  210 . Once in position, the rod can be secured in place using the screw  303 , the two flat washers  302  and the nut  304  as shown. Then using the rod  300  as a means for pulling on the magazine follower  210  against the follower spring (not shown), the magazine follower  210  can be retracted into the magazine  200  and the rod  300  secured temporarily in this position using retraction spacer  301 . With a properly sized retraction spacer  301 , the magazine follower  210  will be retracted sufficiently to make opening  202  accessible to the magazine retention fitting  152 . Once magazine  200  is secured into the magazine well  41  of the alternative lower receiver  45 , the bolt catch  120  can be installed while the magazine follower  210  is still retracted. Once installation of the bolt catch  120  is complete, the retraction spacer  301  can be removed, the magazine follower  210  can be allowed to return to its fully extended position, nut  304  and its associated washer  302  can be removed, and rod  300  can be withdrawn. 
     Referring to  FIGS. 4, 15, 16 and 17 , alternate retention fitting  152 A is designed to semi-permanently fix the magazine in a standard lower receiver  35 . The rectangular section of retention fitting  152  defined by sides  155  has been extended by an additional length equivalent to the length of the cylindrical section defined by sides  154  for retention fitting  152  such that the rectangular section aligns with and slideingly passes through both the opening  202  in magazine  200  and the magazine catch slot  13  of a standard lower receiver  35 . The overall length of retention fittings  152  and  152 A is thus the same. While this embodiment of the retention fitting would allow the lower receiver to be reconfigured back to its original capability for accepting a detachable magazine  200 , the level of effort and time to do so could be controlled by the means of affixing the modified retention fitting  152 A into the standard lower receiver  35 . For example, if the modified retention fitting  152 A were configured as a deformable rivet, reverting to a configuration capable of readily accepting a detachable magazine would require grinding, filing or drilling away the deformed head of the retention fitting, a process that would require at least several minutes and would be an obvious (and potentially illegal) modification when completed. Similarly, use of an anti-tamper screw, one which can be easily installed, but is very difficult to remove, would make the conversion process time consuming and require special tools. 
     Referring to  FIGS. 4, 9, 10 and 15 , the alternative lower receiver  45 , the magazine assembly  200 , a retention screw (or rivet)  151 , a retention fitting  152 , and a bolt catch pivot screw  121  can be included together in a parts kit, with or without a standard Lower Parts Kit (a commercially available group of components including, for example, a hammer, trigger, a connector, bolt catch, various pins and springs—not shown in any of the FIGS., but well known in the industry), to create an alternative lower receiver assembly  40  that can be easily substituted for a standard lower receiver assembly  30 .