Abstract:
This tool makes it possible to more conveniently handle the “selector” element on a conventional M16/M4 family weapon when the selector must be removed or reinserted. As will be appreciated by those in the gun repair trade, in the disassembly or reassembly of such weapons the handling of the selector element is a tricky and painstaking activity. This disclosed tool handily is an assist in such activities. The tool is inserted in the opening in the receiver of the selector element and rotated. An offset circular cam means on the tool when rotated will handily depress the detent element (which necessarily must be done and it also has a spring beneath it). A bumper end cap at the distal end of the tool will carefully engage the selector element to gently push on it if needed (or in the reverse operation for the tool to be gently backed away there from as the selector is repositioned into the weapon). A longitudinal groove on the cam means will signal to the user when the proper rotation has been achieved to adequately depress said detent element.

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 makes it possible to more conveniently handle the “selector” and other allied elements on a conventional M16/M4 family weapon when the selector and/or other elements need to be removed or reinserted. As will be appreciated by those in the gun repair trade, in the disassembly or reassembly of such weapons the handling of the selector and allied elements is a tricky and painstaking activity, greatly needing improved assist. This disclosed tool handily is a great addition and assist 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, 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. 
     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 fire control group (i.e., mechanism, assembly, etc.) of such weapons, e.g., hammer, trigger, disconnector (or intermediate sear), selector (i.e., safety selector, safety, or control member), auto sear for selective fire weapons, associated springs and pins, as is well known to those skilled in the art of the assembly, maintenance, and repair the weapons of the are often removed and installed (or reinstalled). U.S. Pat. Nos. 3,045,555 and 5,760,328 describe examples of the fire control components of the conventional M16 rifle. 
     Operations that require the removal and installation of the fire control group (FCG) components of the weapon, in particular the trigger, disconnector and disconnector spring subassembly (i.e., trigger subassembly), is problematic because the selector obstructs ready access to the trigger subassembly. Many repair and maintenance instructions recommend removal of the selector to provide the desired access to the trigger subassembly. However, the selector is retained via a selector detent and spring that are in the firearm lower receiver and which are retained by the firearm hand grip which is, in turn, retained by a screw inside the grip. The grip retention screw fastens into the lower receiver. 
     Unfortunately, the removal of the grip screw and grip, and selector detent and selector detent spring has a number of deficiencies. Such deficiencies include (i) the process is time consuming; (ii) there is risk of loss of components, especially loss of the relatively small selector, detent and selector detent spring; (iii) usually requires repositioning the lower receiver; (iv) risks stripping the grip screw threads in the lower receiver which generally ruins or requires expensive repair to the lower receiver; and (vi) when a Allen head grip screw is used to retain the grip as is common in some commercial weapons, requires a special, long reach Allen wrench which is often an additional expense. 
     Because of such deficiencies, a number of alternative conventional approaches have been implemented to remove and reinstall the selector without removing the grip (and the selector detent and selector detent spring). Selector removal can be performed by cocking the hammer or otherwise depressing the rear of the trigger and rotating the selector to a position intermediate to the ‘safe’ and ‘fire’ (or ‘semi’) detent hole locations, and then pressing the selector out (that is, to the left). The step of pressing the selector out is generally aided by the use of a non-scratching, cylindrically shaped tool having a diameter less than the diameter of the selector such as a wooden or plastic dowel, a push tool (for example, a pin push tool as shown in  FIG. 1 ), or the like. Re-installation of the selector with the detent still in place is; however, typically more problematic. Conventional alternatives to reinstall the selector, with the respective deficiencies, have been used with limited success. 
     One conventional approach to reinstall the selector is to depress the detent with an appropriately sized flat blade screwdriver (or a round punch) with one hand, and with the other hand, the selector is held rotated intermediate to the ‘safe’ and ‘fire’ detent hole locations and slid to the right and back into place. Such a procedure has the deficiencies of (i) the detent is typically pointed and thus difficult to properly depress with the screwdriver blade or punch end which slips off the detent point; (ii) the detent spring is strong and so the detent is difficult to hold down; (iii) there is risk of scratching the selector or the lower receiver finish with the screwdriver blade or punch end; (iv) the lower receiver obstructs the view of the detent; and (v) the technique requires some degree of coordination, dexterity, skill and practice as there is difficulty maneuvering the screwdriver or punch and manipulating the selector in different directions and with different movements simultaneously. 
     Another conventional approach is to depress the detent with an appropriately sized slanted end tool similar to a tool that is sometimes used to install the firearm pivot pin detent; rotating the tool; and sliding the selector back in place. However, such a tool has does not have lateral support as does a front pivot pin detent tool, and hence, has similar deficiencies to the procedure of using a screwdriver or punch noted above. 
     Yet another conventional approach is to rotate the selector intermediate to the ‘safe’ and ‘fire’ (or ‘semi’) detent hole locations, and attempt to rapidly slide and wiggle the selector to the right and back into place. Such attempts generally only result in damage to the selector and/or the detent, and failure to reinstall the selector as selectors typically do not have a sufficiently and appropriately beveled edge to adequately depress the detent to provide for reinstallation. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The description herein assumes the level of knowledge held by an ordinary armorer, gunsmith, repair or assembly technician, 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 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. 
     For ease of description and explanation, U.S. Pat. No. 3,045,555, issued Jul. 24, 1962 to E. M. Stoner, titled “Automatic trigger mechanism with three sears and a rotatable control member”, (the &#39;555 patent) is hereby incorporated by reference in its entirety. As is known to one of ordinary skill in the art, the &#39;555 patent illustrates and describes the fire control mechanism of the conventional M16 pattern rifle and/or M4 pattern carbine. The conventional AR-15 rifle implements a simplified (i.e., semi-automatic fire) version of the fire control mechanism of the &#39;555 patent. In particular, referring to the &#39;555 patent on FIGS. 2 and 3 and at col. 3, line 20 through col. 4, line 41, the physical layout and operation of the relevant components of the firearm fire control mechanism is illustrated and described. The numbering of elements of the &#39;555 patent (i.e., elements having numbers below 200) are implemented for description of the environment which is described herein. The environment forms no part of the invention. 
     The description as follows is directed to a firearm selector removal and installation tool  200  (wherein elements of the tool  200  are numbered 200 and above), and includes directional designations such as up, down, left, right, lateral, transverse, longitudinal, 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 designated element 10 in the &#39;555 patent) as typically held and operated (e.g., fired). 
     The description is generally related to and made in connection with the fire control group (FCG) (i.e., mechanism, assembly, etc.) of such weapons, e.g., hammer  62 , trigger  50 , disconnector (intermediate sear)  68 , selector (common control member, rotatable control member, safety selector, safety) numbered as 120 in the&#39;555 patent, auto sear  96  for selective fire weapons, and associated springs and pins of 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 selector generally rotatably controls the mode of operation (e.g., safe, semiautomatic, burst, or full automatic fire) of the gun  10 . The description is generally applicable to removal and installation of the selector, and the installation tool  200  may be advantageously implemented in connection with, other firearms having the same or similar FCGs. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a conventional, prior art AR-15/M16 rifle and M4 carbine pin push tool; 
         FIG. 2  is an isometric view of a firearm selector removal and installation tool of the present invention; 
         FIG. 3  is a simplified end view that illustrates some relative dimensions and positions of elements of the tool of  FIG. 2 ; 
         FIG. 4  is a broken view of a portion of the right side a firearm receiver from the inside looking left that illustrates the tool of  FIG. 2  as installed during the selector installation process prior to rotation of the tool; 
         FIG. 5  is a partial sectional view of the right side of the firearm receiver from the rear that illustrates the tool of  FIG. 2  during the selector installation process after rotation of the tool; 
         FIG. 6  is a partial sectional view of the right side of the firearm receiver from the rear that illustrates the tool of  FIG. 2  during the selector installation process after rotation of the tool, and also illustrates further details of the tool; 
         FIG. 7  is an end view of a collar that comprises a component of the tool of  FIG. 2 ; and 
         FIG. 8  is a broken side view of an alternative embodiment of the collar of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a conventional, prior art AR-15/M16 rifle and M4 carbine pin push tool; Referring to  FIG. 2 , an isometric view of the firearm selector removal and installation (or insertion) tool (i.e., apparatus, device, unit, etc.)  200  is shown. The tool  200  is generally implemented in connection with removal and installation of the selector of a conventional AR-15/M16 pattern rifle and/or M4 pattern carbine  10 , and variants thereof (i.e., firearm, weapon, etc.) having a lower receiver (e.g., the receiver  14 ). The selector is mounted within the receiver  14  in two circular apertures (openings, holes) that are laterally situated across from each other in the left and right sides of the receiver  14  (see, for example, the &#39;555 patent on FIG. 3). The end of the selector having control handle  122  is mounted in the left side of the receiver  14  and the end of the selector having control cam  124  is mounted in the right side of the receiver  14 . The firearm tool  200  is generally used by a user such as an armorer, gunsmith, repair or assembly technician, maintenance personnel, and the like. 
     The tool  200  has a generally screwdriver like shape. The tool  200  generally comprises a handle  202 , a support shaft  204 , a detent cam  206  having a groove  208 , a collar  220 , and a bumper  230 . The tool  200  has a first end (handle  202  end) and a second end (cam  206  end). The handle  202 , the support shaft  204 , and the detent cam  206  are a generally longitudinal, integral unit  200 . 
     The handle  202  generally includes longitudinal grooves and/or swells, stippling, and the like to aid user gripping and twisting the tool  200 . The handle  202  is generally made of a tough, durable plastic such as nylon or urethane. In alternate embodiments, materials such as wood or metal may be implemented. 
     The support shaft  204  is generally integral to the handle  202 , and the support shaft  204  is generally coaxial with the handle  202 . The support shaft  204  is typically made of tough, durable plastic. The support shaft  204  may be molded integral with or inserted into the handle  202 . 
     The detent cam  206  is generally made of steel or a similar strong, hard metallic substance. The cam  206  is generally molded integral into or inserted into the support shaft  204  and handle  202 . 
     The collar  220  (described in further detail in connection with  FIGS. 6-8 ) may be ring shaped, and generally fits snugly but rotatably around the shaft  204 . The collar  220  is typically made of tough, durable plastic. 
     The bumper  230  (described in further detail in connection with  FIGS. 5 and 6 ) is generally installed into the outer end of the cam  206 . The bumper  230  is typically made of tough, durable plastic. 
     Referring to  FIG. 3 , a simplified end view of the second end of the tool  200  illustrates the spatial relationship of the shaft  204  and the cam  206 . The shaft  204  has a diameter, D 1 , and the cam  206  has a diameter, D 2 , that is smaller than the diameter D 1 . The cam  206  is offset relative to the shaft  204  such that the outer circumference edge of the cam  206  containing the groove  208  coincides with the outer circumference edge of the shaft  204 . 
     Referring to  FIG. 4 , a broken view of a portion of the right side of the firearm receiver  14  from the inside looking left illustrates the tool  200  as installed during the selector installation process prior to rotation (twisting) of the tool  200 . When the selector is not mounted in the right side of the receiver  14 , the detent  130  is biased upward by spring  132  (seen in  FIG. 5  and  FIG. 6 ) to a protrusion (or extended) height, H. When protruded, the safety detent  130  generally prevents installation of the selector  120 . As such, the detent  130  should be depressed to enable the installation of the selector  120 . 
     The diameter of the support shaft  204 , D 1 , is selected such that the shaft  204  fits snugly but rotatably in the hole in the receiver  14  for the end of the selector that contains the control cam  124  when the selector is mounted in the receiver  14  (i.e., the diameter, D 1 , may be about the same diameter as the diameter of the ends of the selector). The diameter of the detent cam  206 , D 2 , is selected to provide clearance to the protrusion (i.e., extended) height, H, of the detent  130  such that, with the cam  206  at the top, the cam  206  may be inserted into the receiver  14  (generally from right to left). When the tool  200  is inserted into the receiver  14 , the groove  208  is generally at or near the top. During the selector installation operation, after insertion into the receiver  14 , the tool  200  may be rotated either clockwise or counter-clockwise to depress the detent  130  via camming action of the outer radial surface of the detent cam  206  and, thereby, enable insertion of the selector (from left to right). 
     Referring to  FIG. 5 , a partial sectional view of the right side of the firearm receiver  14  from the rear illustrates the tool  200  during the selector installation process after rotation of the tool  200 . The receiver  14  has a thickness, RT; and the detent  130  has a point that is inward from the right outside surface of the receiver  14  at an inward offset, PD. The shaft  204  extends from the handle  202  at a length, L 1 ; and the cam  206  extends from the shaft  204  at a length, L 2 . The top (or head) of the bumper  230  has a thickness, BT. 
     The dimensions of the elements that comprise the tool  200  are selected (e.g., calculated, determined, chosen, and the like) such that when the tool  200  is inserted into the receiver  14 , rotation of the tool  200  will depress the detent  130  such that the selector may be readily inserted (generally from the left to the right) into the receiver  14 . In particular, the length L 1  is generally selected such that the support shaft  204  remains within the outer wall of the receiver  14  (i.e., to the right of the hole that contains the detent  130 ). The length L 2  is generally selected such that the cam  206  extends inward beyond the point offset, PD, and, preferably but not necessarily, beyond the inner edge of the hole that contains the detent  130 . However, the sum of the lengths L 1  plus L 2  plus the outer thickness of the bumper  230 , BT, is less than the thickness RT such that a gap, G, that provides clearance such that the control cam  124  end of the selector may readily be guided (piloted) into the respective mounting hole in the receiver  14 . 
     The groove  208  generally has a depth that is selected to provide the user with a tactile and audible click when the point of the detent  130  is engaged into the groove  208  during rotation of the tool  200  while depressing the detent  130  sufficiently to enable the selector to be readily inserted into the right wall of the receiver  14 . The diameter of the bumper  230  is selected such that the outer circumference of the bumper  230  is slightly inside the groove  208 . 
     Referring to  FIG. 6 , another partial sectional view of the right side of the firearm receiver  14  from the rear illustrates further details of the tool  200 . The collar  220  has a thickness, T, and the collar  220  is snugly but rotatably mounted in a circumferential groove  212  in the shaft  204 . The bumper  230  generally comprises a head section that is at the outer end of the detent cam  206  and a push-in retainer section having a generally cylindrical stem with multiple layers of flexible radial fins thereon (typically called in the art a “Christmas-tree” retainer). 
     During a process to remove the selector, the head section of the bumper  230  may be advantageous implemented as a push tool and operated similarly to a conventional push tool. During a process to install the selector, the selector is held at a position between “safe” and “fire” and is pushed left to right, and the selector ejects the tool  200 . The head section of the bumper  230  generally provides reduction or elimination of damage to the finish of the outer right end of the selector during removal and installation processes. The “Christmas-tree” section of the bumper  230  may be installed in a respective appropriately sized hole in the cam  206 . The hole in the cam  206  is generally threaded to aid retention of the bumper  230  in the cam  206 . 
       FIG. 7  is an end view of the collar  220 . The collar  220  generally has a flat ring shape. Referring to  FIGS. 6 and 7  simultaneously, the collar  220  has an inner diameter, D 3 , and an outer diameter, D 4 . The thickness T and the diameter D 3  are selected to provide the snug but rotatable fit to the groove  212  on the shaft  204  as noted. The diameter D 4  is sized such that the collar  220  extends radially outward past the shoulder of the handle  202 . When the tool  200  is inserted in the receiver  14 , the collar  220  generally is stationary against the outer wall of the receiver  14  when the tool  200  is rotated. As such, the collar  220  may reduce or prevent friction against and damage to the finish of the outer surface of the receiver  14 . 
     Referring to  FIG. 8 , a broken side view of an alternative embodiment of the collar  220  is illustrated. To aid installation onto the shaft  204  and rotatability when the tool  200  is operated, the collar  220  may include a plurality of scallops (flaps, petals)  222  on the inner edge. 
     To summarize operation of the tool  200 , during the removal of the selector, the tool  200  is implemented somewhat similarly to a conventional punch or push tool. The selector is rotated to a position intermediate to (between) the “safe” and “fire” positions; the bumper  230  is placed against the right end of the selector; and the tool  200  is firmly and rapidly pushed from right to left to eject the selector. 
     To install the selector, the tool  200  fully is inserted into the selector hole from the outside into the right side of the receiver  14 , right to left, with the cam  206  at the top (e.g., as illustrated in  FIG. 4 ); the tool  200  is rotated either clockwise or counter-clockwise and the radial outer surface of the detent cam  206  depresses the detent  130  until the detent  130  clicks into the groove  208 ; the selector is held at a position between the “safe” and “fire” positions and inserted through the left side of the receiver  14  across and into the right side of the receiver  14 ; via piloting provided by the gap, G, the selector is aligned with the bumper  230 ; the selector is firmly and rapidly pushed to the right against the bumper  230 ; and the tool  200  is ejected as the selector slides into place (and is held in place by the detent  130 ). 
     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.