Abstract:
This trigger guard roll pin tool makes it possible to safely and quickly install or remove the trigger guard roll pin on a conventional M16/M4 family weapon. In the disassembly or reassembly of the trigger guard on such weapons the handling of the trigger guard roll pin element is often a manually challenging and painstaking activity that can result in damage to the weapon if done incorrectly. This disclosed tool handily is an assist in such activities. The trigger guard roll pin tool makes it possible to remove and install the trigger guard roll pin without risking breakage of the roll pin flanges on the lower receiver.

Description:
U.S. GOVERNMENT INTEREST 
     The inventions described herein may be made, used, or licensed by or for the U.S. Government for U.S. Government purposes. 
    
    
     BACKGROUND AND SUMMARY OF INVENTION 
     This tool generally makes possible more convenient handling of the removal and installation of a roll pin that retains a trigger guard in a lower receiver on a conventional M16/M4 family weapon when the installation or removal of the trigger guard, hence the installation or removal of the retaining roll pin, is desired. As will be appreciated by those in the gun repair trade, the disassembly or reassembly of the trigger guard and allied elements (e.g., the roll pin) of such weapons is a challenging, tricky and painstaking activity sometimes resulting in damage to the lower receiver, thus greatly needing improved assist. The disclosed tool handily is a great addition and assists in such activities. 
     The description as follows includes directional designations such as up, down, left, right, lateral, transverse, longitudinal, top, bottom, vertical, and the like, that are taken from the perspective of a firearm (e.g., a conventional AR-10/AR-15/M16 family, style, platform, or pattern rifle and M4 pattern carbine, and variants thereof) as typically held and operated by a user. 
     The description assumes the level of knowledge held by an ordinary armorer, gunsmith, repair or assembly technician, user, operator, maintenance personnel, and the like for a conventional AR-15/M16 pattern rifle and M4 pattern carbine, and variants thereof, and the respective components and operation thereof. The environment forms no part of the invention. Likewise, designations such as “a”, “an”, and “the” are not to be construed to be limited to a singular item or action unless apparent from the context or definitely described as such. 
     As used herein, elements having numbers more than  9  and less than  100  generally refer to conventional elements known in the art by one having ordinary skill with respect to a rifle, firearm, weapon, carbine, and the like; generally AR-10, AR-15/M16 rifle, M4 carbine families; while elements number  100  and above refer to the present invention, or elements, components, and the like thereof. Like numbered elements generally refer to the same element; however, the like numbered elements may include a suffix “L” to designate the left side element and a suffix “R” to designate the right side element when left and right elements are mirrors of each other. 
     Conventional elements include:
       10 : lower receiver assembly;     12 : trigger guard;     14 : trigger guard retention roll pin;     16 : pistol grip (hand grip) mounting flange;     20  ( 20 L,  20 R): trigger guard retention flange (tang, ear, wing, and the like), roll pin flange;     22  ( 22 L,  22 R): trigger guard roll pin hole (lateral hole in the flange  20 );     30 : hand grip retention screw hole;     32 : hand grip retention screw;     34 : selector (safety, fire control lever);     40 : pin punch;     42 : hammer;     44 : pad, block, or the like;   TO: tang offset (inward offset of the trigger guard tangs  20  from the outer surfaces of the lower receiver  10 );   U: User, armorer, gunsmith, repair or assembly technician, operator, maintenance personnel, aid the like.   

     As further understood by those having ordinary skill in the art, the conventional M16/M4/AR-15 family weapons are made to an exacting technical data description that is agreed upon by manufacturers of not only the firearms but the numerous aftermarket accessories as well; and, as such, provides interchangeability and modularity within and between manufacturers using such designation. As such, designation of the subject firearms as being within M16/M4/AR-15 family weapons provides the indication (designation) of de facto standardization of the components so designated. Thus, such designation is distinct and particular as used in connection with claims directed thereto. 
     During assembly and repair operations of AR-15/M16 pattern (style or family) rifles and M4 pattern (style or family) carbines (i.e., weapons), and variants thereof (referred to as guns, weapons, or firearms hereafter), the trigger guards (i.e., mechanism, assembly, devices, etc.) of such weapons, as is well known to those skilled in the art of the assembly, maintenance, and repair of the weapons, are often removed and installed (or reinstalled). Such operations may include tasks such as but not limited to initial firearm assembly, installation of new trigger guards to replace damaged trigger guards, upgrading of trigger guards, etc. 
     Referring to  FIGS. 1-3 ,  FIGS. 1-3  illustrate conventional, prior art AR-15/M16 rifle and M4 carbine pattern lower receivers  10 .  FIG. 1  is a left side elevation of a bare (stripped) lower receiver  10 . The lower receiver  10  shown on  FIG. 1  is intact.  FIG. 2  is an isometric view from the upper, right, front with inset  2 A which is an isometric view from the upper, right, rear that illustrates the user, U, using the conventional tools (i.e., the punch  40 , the hammer  42 , and the pad  44 ) during the process of trigger guard retention roll pin  14  installation or removal.  FIG. 3  is an isometric view of the receiver  10  from the lower, left, rear that illustrates an example of a flange  20 L that was broken during an unfortunate but all too common failed attempt to install the trigger guard retention roll pin  14 . 
     During assembly, repair, and replacement operations of the AR-15/M16 pattern rifles and M4 pattern carbines (i.e., firearms, weapons, etc.)  10 , and variants thereof, a trigger guard element  12  of the lower receiver  10  may be installed or removed. As understood by one of skill in the art, e.g., an armorer, gunsmith, user, operator, repair or assembly technician, maintenance personnel, and the like, U, the rear portion of the trigger guard  12  is held (retained) in the lower receiver  10  by a tension pin (e.g., roll pin, split pin, C pin, spiral pin, coil pin, etc.)  14  that is inserted between (driven into) lateral holes  22  (e.g., holes  22 L and  22 R) within laterally opposing first and second flanges (tangs, tabs, ears, etc.)  20  (e.g., ears  20 L and  20 R) on the lower receiver subassembly  10  of the firearm forward of the hand grip mounting region (e.g., a hand grip flange  16 ) and through an intervening lateral hole (channel, passage, etc.) in the rear of trigger guard  12 . The most commonly used tension pin is a roll pin (split pin). As such, hereinafter, the tension pin  14  is non-exclusively referred to as a roll pin. The hand grip flange  16  includes a threaded hole  30 , which matingly receives a threaded screw or bolt  32  (see, for example,  FIGS. 5-7 ) to retain a hand (pistol) grip (not shown) as part of the assembly process, as understood by one skilled in the art. 
     As illustrated on  FIG. 2  including inset  2 A, conventional tools and a conventional process that have been used for AR-15/M16 rifle and M4 carbine  10  trigger guard roll pin  14  installation and removal include a pin punch (i.e., punch with a flat tip)  40 , a hammer  42 , and an impact resistant pad or block  44  that is placed behind the lower receiver  10  at the roll pin flange  20  that is opposite the side from which the roll pin  14  is inserted. The pad  44  is typically placed on a work bench or table (not shown). The user, U, manually positions the trigger guard  12 , laterally aligns the roll pin  14 , and drives the roll pin  14  into position through the holes  22  via taps, hits, blows, and the like to the punch  40  with the hammer  42 . Alternatively (not illustrated), the roll pin  14  may also be pressed (squeezed) into position through the holes  22  (e.g., pressed using a C-clamp, pliers, or the like) laterally positioned across the roll pin tangs  20 ; however, the pressing of the roll pin  14  approach also has the same occasional, undesirable consequences (i.e., breakage of a roll pin flange  20 , described below in connection with  FIG. 3 ) as drying the pin  14 . 
     Unfortunately, as illustrated on  FIG. 3 , even when care is taken by attempting to remove burrs, lubricate, and correctly align the roll pin  14  with both of the lower receiver flange holes  22 L and  22 R (and the intervening hole through the rear of the trigger guard  12 ) and the impact pad  44  is carefully positioned, occasionally the roll pin  14  insertion or removal process will go awry and one of the roll pin flanges  20  is broken off the lower receiver  10 . As the lower receiver  10  is a costly and federally regulated (i.e., registered as a firearm) part, breaking the lower receiver  10  is a potentially costly burdensome occurrence. On  FIG. 3 , the distance, TO, illustrates a tang offset by which the trigger guards  20  are offset inward from the outer lateral surfaces of the receiver  10 . 
     The broken receiver  10  may be rendered inoperable by the user and discarded. Alternatively, users who break one or both roll pin flanges  20  may: (i) repair the broken flange  20  with expensive welding, grinding, and refinish processes; (ii) repair the broken flange  20  with a relatively weak epoxy joint and hope that the broken flange  20  does not encounter any mechanical stress; or (iii) hide the broken flange  20  with a commercially available pistol grip that incorporates a trigger guard (e.g., STARK SE-1 grip, MAGFUL MIAD (registered trademark) grip) which may be costly and uncomfortable to the user. So common is the breakage of the flange  20 , that the replacement grips that hide the broken roll pin flange  20  are often referred to, sometimes with Schadenfreude, as “the grip of shame”. Clearly, a better approach is to not break the roll pin flange  20 . 
     A conventional approach to avoid breaking the roll pin flange  20  is to not use a roll pin  14 , instead to: tap threads or install thread adapter inserts into the holes  22 , and install low profile head screws to retain the trigger guard  12 . However, such an approach has the deficiencies of being expensive, requires special tools and skills to perform, may defeat the swing down (“winter”, i.e., thick glove use) feature of the trigger guard  12 , the trigger guard  12  may be loose (flop, wiggle), and the screws may back out unless additional steps such as adding retention compound are taken which may make removal of the screws difficult. 
     Thus, there is a need and a desire for a system and a process that overcomes one or more of the deficiencies of conventional devices and processes. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The description herein assumes the level of knowledge held by an ordinary armorer, gunsmith, repair or assembly technician, user, operator, maintenance personnel, end the like for a conventional AR-15/M16 pattern rifle and M4 pattern carbine, and variants thereof, and the respective components and operation thereof. The description may include directional designations such as up, down, left, right, lateral, transverse, longitudinal, top, bottom, vertical, and the like, that are taken from the perspective of a firearm (e.g., a conventional AR-10/AR-15/M16 family, style, platform, or pattern rifle and M4 pattern carbine, and variants thereof) as typically held and operated by a user. 
     The present invention is directed to an armorer or gunsmith tool. In particular, the invention is a tool used as a trigger guard roll pin installation and removal process aid for AR-15/M16 rifles and M4 carbines. AR-15/M16 pattern rifles and M4 pattern carbines, and variants thereof, are very prolific having been produced more or less continuously since first introduced circa 1961. Such firearms are found throughout the world with millions of copies of each produced, and in use by numerous civilian personnel, and law enforcement and military agencies including use as the standard infantry firearm in much of the U.S. military. The invention is a tool that may be implemented in connection with an AR-15/M16 rifle and M4 carbine lower receiver to quickly and easily provide trigger guard retention roll pin installation and removal and prevent damage to the firearm, specifically breakage of the trigger guard retention flanges, at a relatively low cost. The invention will generally help reduce or prevent damage to components of the firearm during assembly, repair, and replacement operations. 
     The invention provides a secure, robust, relatively low cost trigger guard roll pin installation and removal tool for easy and convenient use in connection with a conventional AR-15/M16 pattern rifle and M4 pattern carbine firearms, and variants thereof. The invention securely mounts on a conventional lower receiver at the pistol grip mounting location (i.e., the pistol grip flange  16 ); and provides positive, stable support of the lower receiver flange  20  to reduce or prevent likelihood of breakage of the trigger guard pin flanges  20  during trigger guard retention pin  14  installation and removal processes. The trigger guard roll pin tool is quickly and easily removed when the desired tasks are completed. Mounting is achieved by mounting the trigger guard roll pin tool on the pistol flange  16  and securing the tool via the standard pistol grip (hand grip) screw  32  or similarly sized and threaded bolt, screw, wing bolt, or the like installed into the hand grip screw hole  30 . Furthermore, the trigger guard roll pin tool may be used when the fire control selector  34  remains installed in the lower receiver  10 . Thus avoiding the lost time involved with removal and re-installation of the selector  34 . 
     For the user, U, to determine whether the roll pin  14  is driven in to the proper depth (i.e., not too shallow and not too deep) during installation, or when the roll pin  14  has been driven out during removal; techniques such as (i) visual inspection, (ii) insertion of a shim or other thin device between the tool and the flanges of the lower receiver, (iii) inspection of the length of the pin punch  40  shaft portion that extends outside of the installation guide tool, or the like can be used. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a left side elevation view that illustrates a bare (or stripped) conventional, prior art AR-15/M16 rifle lower receiver section; 
         FIG. 2  is an isometric view from the upper, right, front isometric view from the upper, right, rear with an inset  2 A; 
         FIG. 3  is an isometric view of a broken example of the receiver  10  from the lower, left, rear; 
         FIG. 4  is an isometric view from the left, front, upper point of view of the trigger guard roll pin tool invention; 
         FIG. 5  is a left side elevation view that illustrates the tool of  FIG. 4  as installed a conventional lower receiver at the pistol grip mounting location, and also illustrates the installation screw; 
         FIG. 6  is a right side elevation view that illustrates the tool of  FIG. 4  as installed a conventional lower receiver at the pistol grip mounting location; 
         FIG. 7  is a bottom view that illustrates the tool of  FIG. 4 . as installed a conventional lower receiver; 
         FIG. 8  is a top (plan) view of the tool of  FIG. 4  as installed on a conventional lower receiver at the pistol grip mounting location and illustrates the support that the tool of  FIG. 4  provides, as a well as clearance that the tool provides for the selector; 
         FIG. 9  is a top view that illustrates the tool of  FIG. 4 ; 
         FIG. 10  is a front view of the tool of  FIG. 4 ; 
         FIG. 11  is a rear view of the tool of  FIG. 4 ; 
         FIG. 12  is a right side elevation view of the tool of  FIG. 4 ; 
         FIG. 13  is a sectional view taken at line  13 - 13  of  FIG. 9 ; wherein  FIG. 13  illustrates detail of the interior of tool of  FIG. 4 ; 
         FIG. 14  is a sectional view taken at line  14 - 14  of  FIG. 9 ; wherein  FIG. 14  illustrates additional detail of the interior of tool of  FIG. 4 ; 
         FIG. 15  a sectional view taken at line  15 - 15  of  FIG. 9 ; wherein  FIG. 15  illustrates additional detail of the interior of tool of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 ,  2 , and  3 , as described above, illustrate the conventional, prior art AR-15/M16 rifle and/or M4 carbine lower receiver  10 , and the use of conventional hand tools during installation and removal of the trigger guard retention roll pin  14 . 
     The description as follows is directed to a trigger guard roll pin tool  100  (wherein elements of the tool  100  are numbered  100  and above), and includes directional designations such as up, down, left (L), right (R), lateral, transverse, longitudinal, front, forward, back/backward/rearward, top, bottom, vertical, and the like, that are generally taken from the perspective of a firearm (gun, weapon, and the like, e.g., a conventional AR-10/AR-15/M16/M4 family, style, platform, or pattern rifle and carbine, and variants thereof as typically held and operated (e.g., fired). 
     The description is generally related to and made in connection with the AR-15/M16 pattern (platform, style, or family) rifles and M4 pattern carbines (i.e., weapons), and variants thereof (referred to as guns, weapons or firearms hereafter). The description is generally applicable to removal and installation of the retention roll pin  14  for the trigger guard subassembly  12  (e.g., the roll pin  14 ), and the tool  100  may be advantageously implemented in connection with other firearms having the same or similar trigger guards. The trigger guard roll pin tool  100  is generally mounted on the lower receiver  10  in lieu of the hand grip to aid the removal and installation of the trigger guard subassembly  12 . The trigger guard roll pin tool  100  generally provides a strong, secure, stable support to the trigger guard flange  20  (e.g., the trigger guard flanges  20 R and  20 L) the thus reducing the risk of breakage during removal and installation of the retention roll pin  14 . 
     Elements (numbered  100  and above) of the present invention may include but are not necessarily included in all embodiments and are not limited to:
       100 : trigger guard roll pin tool (apparatus, device, assembly, part, and the like);     102 : mounting body;     104 : flange (tang, ear, wing) support;     106 : spacer;     110 : base (shroud);     120 : grip flange cavity     124 : retention screw hole;     130 : roll pin passage hole;   BT: base thickness (thickness of the base  110  at the outer wall to the left of the spacer  106 )   CD: total clearance distance, is the distance from the inner wall of the base  110  to the left outer edge of the receiver  10 . CD=SC+SD;   R: radius, which is greater than the length of the selector  34  and thereby provides clearance   SC: clearance between the inner wall of the base  110  and the selector  34 ;   SD: distance that the selector  34  extends away (to the left) from the receiver  10 ;   TL: forward extension length of the roll pin flange  20  from the grip mounting flange  16 ;   TT: total thickness, is the distance from the left inner wall of the mounting body  102  to the left outer wall of the base  110 .   

     Referring to  FIG. 4 , an isometric view from the left, front, upper point of view of a trigger guard roll pin tool  100  of the present invention is shown. The trigger guard roll pin tool  100  comprises a mounting body  102 , and successively to the left of the mounting body  102 , a flange support  104 , a spacer  106  and a base  110 . Alternatively (not shown) a right side mirror embodiment of the invention may be implemented instead of the left side embodiment. The right side embodiment may be preferred by left handed users. 
     The tool  100  is generally molded, cast and/or machined from a high (or heavy) density polyethylene (HDPE), ultra high molecular weight polyethylene (UHMWPE or UHMW), high strength nylon (e.g., Nylon 6), DELRIN, RYNITE, filled/reinforced polymer, or metal such as aluminum, steel, brass, or the like. The tool  100  may be formed as a single unit; alternatively, the tool  100  may be an assembly of two or more parts that are securely joined. However, any appropriate material and manufacturing technique (process) may be implemented to meet the design criteria of a particular application. 
     The roll pin tool  100  provides support to the lower receiver flange  20  to reduce or prevent likelihood of breakage of the trigger guard pin flanges  20  during the trigger guard roll pin  14  installation and removal processes. The trigger guard roll pin tool  100  is quickly and easily removed when the desired tasks are started and when completed. The mounting body  102  includes a cavity (void)  120  that is sized and shaped to provide for mounting the tool  100  on the grip mounting flange  16 . 
     The flange support  104  is generally implemented as a step (ledge, ridge, and the like) at the front of the tool  100 . The flange support  104  fits tightly against (e.g., adjacent) the flange  20 L and thereby reduces or prevents flex and breakage of the ear  20 L when the roll pin  14  is driven in or out of (i.e., through) the pin hole  22 L. The spacer  106  spaces the base  110  away from the receiver  10  and provides clearance for the selector  34  such that the selector  34  does not have to be removed from the receiver  10 . The base  110  holds the receiver  10  and provides an impact resistant surface. 
       FIG. 5  is a left side view that illustrates the tool of  FIG. 4  as installed the conventional lower receiver  10  at the pistol grip (hand grip) mounting location  16 . FIG.  5  also illustrates the installation screw  32  which is installed through the retention screw hole  124  and into the grip screw hole  30  to threadedly secure the tool  100  to the receiver  10 . When the trigger guard roll pin tool  100  is installed, no conventional pad  44  is needed (i.e., implementation of the pad  44  may be avoided). The roll pin  14  installation and removal processes can be conducted essentially as illustrated on  FIGS. 2 and 2A  and described above in connection therewith. 
       FIG. 6  is a right side view that illustrates the tool of  FIG. 4  as installed. Also indicated is the forward extension length, TL, of the roll pin flange  20  from the grip mounting flange  16 . The flange support  104  extends forward from the mounting body  102  by at least the forward extension length, TL, to provide support for the roll pin ear  20 . 
       FIG. 7  is a bottom view that illustrates the tool of  FIG. 4  as installed. 
       FIG. 8  is a top view that illustrates the tool of  FIG. 4  as installed.  FIG. 8  illustrates the support that the tool of  FIG. 4  provides via the base  110 , as a well as selector distance, SD, which is the distance that the selector  34  extends away (to the left) from the receiver  10 ; and clearance, SC, between the inner wall of the base  110  and the selector  34 . 
       FIG. 9  is a top view of the tool of  FIG. 4 . The screw retention hole  124  is positioned and sized within the body  102  to align with the grip screw hole  30  and to receive the grip retention screw  32 . The tool  100  is constructed such that the innermost edge of the flange support  104  fits tightly against (i.e., adjacent to) the left trigger guard flange  20 L when the tool  100  is installed on the receiver  10 . 
       FIG. 10  is a front view of the tool of  FIG. 4 . The base thickness BT, is the thickness of the base  110  at the outer wall to the left of the spacer  106 . The total clearance distance, CD, is the distance from the inner wall of the base  110  to the left outer edge of the receiver  10  (see also,  FIG. 11 ). CD=SC+SD. The tang offset, TO, is the inward offset of the trigger guard tangs  20  from the outer surfaces of the lower receiver  10 . The total thickness, TT, is the distance from the left inner wall of the mounting body  102  to the left outer wall of the base  110 . 
       FIG. 11  is a rear view of the tool of  FIG. 4 . The receiver  10  is shown in phantom to illustrate a reference for the total clearance distance, CD. 
       FIG. 12  is a right side elevation view of the tool of  FIG. 4 . The roll pin eject (clearance) hole  130  is illustrated. The roll pin eject hole  130  is horizontally and vertically positioned at a location to directly align with the roll pin hole  22 L, and extends laterally through the flange support  104 , spacer  106 , and base  110  sections of the tool  100  and is sized having a slightly larger diameter than the roll pin holes  22 . As such, during a process to remove the roll pin  14 , the roll pin  14  may be readily driven (tapped) out through the trigger guard  12  and is loosely received into and through the roll pin clearance (eject) hole  130 . 
       FIG. 13  is a side sectional view taken at line  13 - 13  of  FIG. 9 .  FIG. 13  illustrates detail of the interior mounting cavity  120  of tool of  FIG. 4 . The line  13 - 13  is at the center of the retention screw hole  124 . 
       FIG. 14  is a side sectional view taken at line  14 - 14  of  FIG. 9 .  FIG. 14  illustrates detail of the flange support  104  and the spacer  106 . The line  14 - 14  is slightly interior (to the right) of the left edge of the grip flange mounting cavity  120  such that  FIG. 14  illustrates the inner left edge of the cavity  120  as well as interior details of the flange support  104  and the spacer  106 . 
       FIG. 15  is a side sectional view taken at line  15 - 15  of  FIG. 9 . The line  15 - 15  is interior (to the right) of the left edge of the inner wall of the base  110 .  FIG. 15  illustrates additional detail of the spacer  106 . In particular, the spacer  106  has a radius, R, at the top that provides clearance for installation (and rotation, if desired) of the selector  34 , shown in phantom. Note that the spacer  106  is not necessarily formed having a curved surface so long as adequate clearance for the selector  34  is provided. 
     The firearm tool  100  is generally used by a user such as an armorer, gunsmith, repair or assembly technician, maintenance personnel, and the like. However, a home (non-commercial) user may find the trigger guard roll pin tool  100  to be a useful aid as well. 
     While the invention may have been described with reference to certain embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.