Jig for manufacturing of firearm lower receiver

An improved jig for manufacturing a firearm lower receiver is comprised of a power tool mount; an adapter; a guide plate with plate screws; a rear support with mounting screws; a front support; and at least one of a carriages with at least one locating pin. A guide plate is disposed below the top surface of a lower receiver in conjunction with an adapter. The jig is a universal fitment and includes a bearing to support a rotary tool and at least one guiding feature can be used to facilitate in the guidance of the rotary tool without placing the rotary tool in direct contact with any of the guidance features. A removable locating pin is situated a long the front and rear takedown pin holes of a firearm receiver that is not threaded and is provided with at least one of a pull, string or other handle.

FIELD OF THE INVENTION

This invention relates to systems and methods for manufacturing an 80% (partially unfinished) firearm receiver, with a high rate of success with improved quality, by an unskilled user.

BACKGROUND OF THE INVENTION

A market exists for incompletely/partially manufactured firearm lower receivers. A firearm lower receiver is unregulated until a minimum level of manufacturing is completed. This level is typically known as “80%”. Firearm lower receivers completed to this level are typically referred to as “80%” lower receivers. These firearms must then be completed by the end user to be operable. In a typical configuration the lower receiver is cast and/or forged and is partially machined, with certain aspects of the inner slot (in which the trigger mechanism resides) remaining uncut. The finishing task cuts this remaining slot with appropriate dimensions and accuracy.

The completion of these lower receivers can be time consuming and quality results may be difficult to achieve with prior art. In accordance with the prior art, the technique for finishing the receiver can place a rotary power tool in a position that is effectively too far away from the lower receiver. As such this prior art technique can produce poor results and broken tooling. Additionally, the prior art technique can involve placement of a rotating tool in direct contact with guiding areas of a jig, which can result in premature wear.

It would be desirable to provide a jig assembly that effectively reduces the unsupported distance between the rotary power tool and the 80% lower receiver and that avoids direct contact between the rotating tool and its guiding features.

SUMMARY OF THE INVENTION

This invention overcomes the disadvantages of the prior art by providing a device that reduces the distance between the lower receiver and the rotary power tool and by using additional features to guide the rotary tool instead of placing it in direct contact with any of the plurality of guiding features. An improved jig for manufacturing a firearm lower receiver is comprised of a power tool mount; an adapter; a guide plate with plate screws; a rear support with mounting screws; a front support; and at least one carriage with at least one locating pin. A guide plate is disposed around and below the top surface of a lower receiver and is mounted to the carriage(s) in conjunction with a rotary power tool adapter. The jig is a universal fitment. The jig includes a bearing to support a rotary tool and is constructed and arranged to provide for use of at least one guiding feature to facilitate in the guidance of the rotary tool without placing the rotary tool in direct contact with any of a plurality of guidance features for firearm lower receiver manufacturing. A removable locating pin is situated in a location along the front and rear takedown pin holes of a firearm receiver that is not threaded and is provided with at least one of a pull, a string or other handle for firearm lower receiver manufacturing.

DETAILED DESCRIPTION

The primary function of a jig is to provide repeatability, accuracy, and interchangeability in the manufacturing of products. InFIG. 1, an improved jig100is assembled by placing left carriage302(seeFIG. 3, not shown inFIG. 1) on the left side of a lower receiver116and by placing right carriage114, on the right side of the lower receiver116. The lower receiver in this example is a form of popular AR-style receiver (for example the semi-automatic version of the AR-15, M-16, M-4 carbine, and variants thereof). The lower receiver is the portion of the firearm that includes a shoulder stock, pistol grip, trigger mechanism and magazine well. The upper receiver includes the barrel, chamber and bolt assembly. The lower receiver is attached to the upper receiver by two takedown pins. The firearm is available in fully automatic and semi-automatic versions. Note that the jig is adapted to finish the receiver with holes and cuts appropriate to the semi-automatic version. However, the jig can be adapted for the use by licensed manufacturers to finish other versions (e.g. fully automatic) of the firearm. The jig100is an assembly that is comprised of a rotary power tool mount103, an adapter122, a guide plate108with plate screws106,120, a threaded rear support110with mounting screws112, a front support118, and at least one carriage114with at least one locating pin306. As described below, the plate screws106are machine screws with an appropriate diameter, thread size and length, and the screw120can also be a machine screw (for example, a #8-32 flat head machine screw), sheet metal screw, or another form of self-tapping screw. The receiving hole of the front support118is drilled and/or tapped to accommodate the screw120. The illustrative jig defines a universal fitment. A removable locating pin306(SeeFIG. 3) is readily inserted through all three parts302,116and114to hold them in alignment relative to each other. This renders assembly highly straightforward for use by even an inexperienced user. In an embodiment, the jig assembly can be provided as a kit with appropriate instructions (printed, on electronic media and/or available via the Internet). See for example, the instructions in attached Appendix A, which describe setup and use of the jig assembly. The kit can include a rotary power tool having and appropriate size, shape, torque and power supply.

As described herein, the lower receiver116includes a buffer mount117for receiving a buffer assembly within the shoulder stock at one end, and the front surface of the magazine well119at the other. As defined herein, the buffer mount117is at the “rear” end of the lower receiver, while the magazine well119is at the “front” end of the lower receiver. As presented inFIG. 1, the rear end of the lower receiver116is on the left side and the front end of the lower receiver116is on the right side and the visible face of the lower receiver is the “right” side. The right carriage114is resting on the right side of the lower receiver116. Thus, the relative orientation of the jig assembly100(i.e. left, right, front, rear, top and bottom) is described with respect to the corresponding, confronting sides of the lower receiver116.

Note that the carriage plate114is provided with three drill guide holes,132,134,136, along its side for the location of and drilling of appropriate diameter pin holes into the lower receiver116. These guide holes are used to guide and align a drill bit to bore desired holes into the lower receiver side. By way of non-limiting example drill guide hole132is a guide hole for a hammer pivot/pin hole, for the subsequent mounting of an assembly that retains the hammer mechanism within the lower receiver. Drill guide hole134is a guide hole for a trigger pivot/pin hole, for the later mounting of a trigger pivot/pin to retain the trigger mechanism. Drill guide hole136is a guide hole for a selector/safety pivot hole, for the subsequent mounting of a selector/safety lever. These carriage guide holes provide for the accurate and precise placement of the pin holes and are constructed so that an unskilled user can properly place the pivot/pin holes for completion of the assembly of a functioning lower receiver. Holes can be provided on each of opposing carriage plates to drill each side of the receiver in an embodiment. In alternate embodiments holes are provided on one side and the drill passes through both sides of the receiver. The thickness of the carriage plate(s) and close tolerance of the hole to the drill shaft is sufficient to ensure minimal skew or wobble as the drill passes into the receiver side.

The rotary power tool mount103is adapted to receive an appropriately sized and shaped rotary power tool102, as described further below. The rotary power tool retains an appropriate rotary tool104in accordance with various embodiments. The term “rotary tool” shall be taken broadly herein to mean any one of a variety of rotating cutting elements that can be mounted removably (or permanently) within a chuck or arbor of the rotary power tool102. For example a two-flute or four-flute end mill of appropriate diameter (for example, a ¼ inch diameter, or another appropriate diameter between (e.g.) ⅛ inch and ½ inch) can be mounted within the rotary power tool. The mill can include a cutting end and a shaft that is free of cutting surfaces. The shaft is adapted to confront the jig so as to avoid cutting its sides while the cutting end is adapted to reside within the receiver so as to cut the appropriate slot(s) in conjunction with the jig's outline(s). The rotary tool104can be constructed from a variety of high-strength materials, such as high-speed steel, tungsten carbide, etc.

As shown, the rear support110is threaded into lower receiver116via the receiver's rear buffer mount (a large round hole at the rear of the receiver in which a buffer assembly normally resides when assembled into a firearm). Front support118is placed between two mounting ears on the lower receiver116before an easily removable locating pin704inserted through the mounting ears of the lower receiver116and through the hole in the front support118. Illustratively, the front support118resides where the front pivot/takedown pin between the upper and lower receiver on a complete firearm normally resides. The pivot hole in this arrangement has been drilled by the supplier of the 80% receiver, and is, thus available for use in mounting the front support via pin306. As with other receiver holes and structures relied upon to engage the jig assembly, they are reliably located by the manufacturer using sophisticated tooling so that the jig accurately and repeatable mounted to the lower receiver116, and the corresponding cutting performed by the user is equally reliable and accurate.

After mounting the front support118, a guide plate108is then placed atop the assembly by aligning the holes in the guide plate108with the threaded holes in the front support118, the threaded holes in the rear support110, and the threaded holes in both the left and right carriages302and114respectively. The guide plate108has a thickness TC1of between ⅜ and up to ½ inch and a length LC1of approximately 8 inches (±0.5 inches). The adapter plate122has a thickness TC2of approximately ½ inch and a length LC2of approximately 4 inches (±0.5 inches). In other embodiments, these thicknesses and widths can vary greater or lesser, depending on the materials used. Once aligned, carriage-to-guide plate screws106are inserted through the guide plate108and tightened to connect the carriages114and302to the guide plate108. The rear support-to-guide plate screws are inserted through the holes in the guide plate108and tightened into the rear support110. The front support-to-guide plate screws120are inserted through the guide plate108and tightened into the front support118. These screws120can be sheet-metal screws or flat head screws (for example, a #8-32 flat head screw) and the hole(s) in the front support118can be sized to receive such screws. The carriage screw304is threaded to a corresponding female thread in the left carriage302and continued through a threaded hole in the right carriage114. Illustratively, both the left carriage302and right carriages114are threaded so if the assembly is placed into the jaws of an external vice or other clamp, it will tend to resist deformation that could damage the lower receiver116sandwiched therebetween. The screw304can have a recessed drive head (e.g. hex, star, etc.) so that it avoids interference with a clamping jaw (if any). The above thus defines the full set of components of the jig assembly, which are connected either directly or indirectly to the lower receiver116.

The illustrative jig assembly is depicted as retaining a rotary power tool102in the power tool mount103, but it is contemplated that the power tool can be a non-rotary tool. The jig provides for the use of at least one of the various guiding features (for example, left carriage302) to be utilized to aid in the guidance of a power tool102without placing the tool in direct contact with any guiding feature.

Note that a wide variety of rotary power tools can be employed in association with an embodiment of the jig assembly—for example a small router, drill, hand piece of a flexible-shaft unit or Dremel®-style tool. The rotary tool can be cordless or powered by (e.g.) wall current via a power cable.

FIG. 2depicts the jig100holding the rotary power tool102in engagement with the lower receiver116so that finishing work can be performed on the lower receiver. The receiver116is situated between the carriages114and302so that it remains in place during the finishing operation. There is a narrow gap between the carriages and the walls of the lower receiver116. The gap prevents contact between the surfaces of the carriages with the surface of the lower receiver and thereby prevents possible scratching of the surface coating of the lower receiver. In an alternate embodiment, the carriages can have an external flexible coating (for example, a polymer) and make contact with the surface of the lower receiver or a removable foam pad can be provided during assembly to avoid inadvertent contact between the carriage plate and the receiver during assembly of the jig. The various plates of the jig assembly can be constructed from a variety of materials, or combination of materials—for example aluminum alloy, steel, polymer (e.g. Delrin® (from DuPont), polycarbonate, acrylic, etc.). The thickness of each plate108,122is also highly variable, and depends in part upon the choice of material(s). By way of non-limiting example, the thickness of the jig assembly plate(s) can be between ⅛ and ½ inch, or greater, for sufficient strength and rigidity. For example, the carriage plates114and302should define a sufficient thickness to receive the screws106within threaded holes formed in the top edge of each plate. Likewise, the guide plate108should be sufficiently thick to allow the rotary tool104to resist wobble. The various plates can be constructed from sheet stock and milled to shape using, e.g. CNC manufacturing techniques. Other methods of constructing the plates can be employed in alternate embodiments—for example stamping or casting with finish milling, 3D printing, molding, etc.

The following is a description further views and representations of the assembled jig assembly100and corresponding rotary power tool (102) arrangement.

With reference toFIG. 3, a rear-oriented exploded view of the jig assembly100is shown, with the rear support110with mounting screws112visible within the buffer mount117within the lower receiver116. In an embodiment the carriage plates114and/or302can define a thickness TC3of approximately ½ inch (+⅛ inch). This dimension is highly variable in alternate embodiments an, in part, facilitates the formation or female-threaded holes for receiving screws106. Note that, while two carriage plates are employed in the depicted embodiment, at least one carriage plate can be used in alternate arrangements. Such a single plate can include appropriate brackets or other structures to maintain it in confronting, accurate engagement with the lower receiver side.

With reference toFIG. 4a rear view of the assembled jig100is shown in operation on the lower receiver116. The carriage plates114,302are situated on their respective sides of the lower receiver116and are held in place by removable pins306and704. Each of the pins is removably locked in place by a detent307located at one end and a ring309at the other. Opening402in the tool mount103serves to provide air circulation within the area of the machining, a portal for the egress of machining debris and a visible window to allow a view of the machining in process.

FIG. 5is an exploded left side view of the jig100in an assembled state, with a rotary power tool102, a rotary power tool adapter122, a rotary tool104, a guide plate108, a rear support110, a left carriage302, a lower receiver116, a front support118and related mechanisms. The buffer mount117protrudes through guide plate108. Plates108and122support the rotary power tool above the lower receiver116such that the rotary power tool is not resting upon the lower receiver.

As described above, the left carriage plate302is also provided with three drill guide holes,632,634,636, for the location of and drilling of pivot/pin holes into the lower receiver116that are aligned with the right carriage holes132,134and136, respectively and define the same dimensions. In embodiments in which a pin/pivot defines different diameters on each side, or is eccentric the diameter or placement of the left carriage hole can vary relative to that of the right carriage hole.

FIG. 6is a collapsed view ofFIG. 5illustrating; a rotary power tool102, a rotary power tool adapter122, a guide plate108, a left carriage302, a lower receiver116and a front support118.

FIG. 7is an exploded front view of the illustrative jig100. Pin704is positioned to be inserted through takedown pin mounts702, such that the pin704passes through the front support118and the pin mounts702, thereby locking the front support118to the lower receiver116. The pin mounts are through holes in the lower receiver116. In another embodiment, pins306and704can define a bolt with a removable nut for locking the bolt in place.

FIG. 8is a collapsed view of the jig100with particular attention called to the placement of the locating pins306,704in the pin mounts702and are held in place by detents307. The locating pin306is removable and is situated in a location along the front and rear takedown pin holes of a firearm receiver that is not threaded and is provided with at least one of a pull, a string or other handle for firearm lower receiver manufacturing.

FIG. 9is a bottom view of the jig100. The bottom surface of adapter122includes a plurality of wells901of various sizes, angles and shapes disposed across the surface of the adapter122. A rotary power tool support bearing902is inserted into the rotary power tool adapter122(for example—using a press or other biasing device) in a circular well901located near the center point of the adapter122. Bearing902allows movement of a rotary power tool which further supports the rotary tool, thereby increasing rigidity, user control, and thus, quality. The rotary tool104is then inserted into the rotary tool support bearing902and the rotary power tool adapter122is connected to the rotary power tool102by inserting adapter screws906into their respective wells901in the adapter122and tightened into adapter103. The guide pins908are connected to the adapter122by inserting an adapter screw904through the guide pins908and tightened into the adapter plate. The above thus defines the components of the tooling assembly.

In use, the rotary power tool102and mount103and adapter122are placed on top of the guide plate108and assembled, as described above, to form the jig. The guide pins908are placed into the guide cavities1202located within the guide plate108. The rotary tool104protrudes by a predetermined length from adapter122so as to interface with the lower receiver116situated below guide plate108. The geometry of the walls of the lower receiver are generally vertical, with the walls of each side parallel to each other up and down and front to back. This geometry provides an opportunity for the unskilled user to complete the machining of the receiver and the performance of the machining tools is optimized by the stability of the jig. The rotary power tool102, adapter122, rotary tool104, guide pins908, and connecting screws904and906, are then guided within the guide cavities1202. The location of the guide pins908and guide cavities1202are placed as to locate the rotary tool104in a predetermined location within the lower receiver116to achieve the desired results without placing the rotary tool104in direct contact with any components other than the lower receiver116, thus reducing premature wear. Window920is a cutout slot at the rear of adapter122and provides visual and physical access to the lower receiver during machining operations, as well as preventing contact with the buffer mount117.

FIG. 10is a collapsed view ofFIG. 9showing the protrusion of the rotary tool104. Window920is aligned to the rear of the jig.

FIG. 11is a top view of the jig100without the rotary power tool. Indices1102,1104,1106are located along a surface of guide plate108and are depth references for the end milling process. Each of the indices is a cavity, as shown inFIG. 1. Indices1102,1104and1106relate to three different lengths for guide pins and the guide cavities are stepped at three different heights so that as the pins get longer, the guide describes a smaller area. The alignment of the view ofFIG. 11is that the top of the view is the front of the jig and the bottom of the view corresponds to the rear of the jig. Buffer mount117is depicted as protruding through guide plate108.

FIG. 12is the same view asFIG. 11with the rotary power tool adapter viewed as semi-transparent, allowing a better view of a rotary tool104, a guide plate108incorporating guide cavities1202; a lower receiver116and guide pins908residing within their respective wells901. The shape of the guide cavities1202corresponds to the shape of the internal walls of the lower receiver116such that when the rotary tool104is inserted into the lower receiver116, the operator maneuvers the guide pins908against the walls of the guide cavities1202and can accurately machine the internal surfaces of the lower receiver116.

In operation, the user places carriages114and302in a vise or other clamping device to hold steady. The protrusion depth of the rotary tool104is set using indices1102,1104,1106. In practice, this is done by placing rotary tool104within the indices and aligning to the appropriate hash mark for the required milling step and moving the rotary power tool adapter122into contact with the edge of guide plate108therefore setting the protrusion depth to the appropriate hash mark relative to the bottom surface of adapter122

The assembled rotary power tool102, mount103, rotary tool104, adapter122and guide pins908are engaged with the guide plate108and guide cavities1202. When the assemblies are placed atop each other with guide pins908within guide cavities1202the rotary power tool is switched on and rotary tool104begins to rotate at a high rate of angular velocity. The user grasps either the rotary power tool102, mount103or adapter122and slide the adapter122along the guide plate108. The protruding guide pins908contact the walls of the guide1202preventing rotary tool104from milling into the incorrect locations. This task is continued until guide pins908have been translated through the entire guide cavities1202removing all the material that rotary tool104has contacted within the lower receiver116. The rotary power tool102is then switched off and the rotary tool104is allowed to come to rest. The assembled rotary power tool102, mount103, rotary tool104, adapter122and guide pins908are then lifted off of the guide plate108. The rotary tool104is then placed back into indices1102,1104,1106to adjust the protrusion depth to the next hash mark of the respective index. When the depth is properly set, the assembled rotary power tool102, mount103, rotary tool104, adapter122and guide pins908are re-engaged with guide plate108and guide cavities1202. The same procedure is followed to remove this material with rotary tool104from lower receiver116. This procedure is similarly followed until all material is removed from lower receiver116. Chips can be removed periodically during each cutting task using a vacuum or by rotating the receiver and jig assembly upside down.

In order to guide rotary104properly in lower receiver116to allow for proper function, guide cavities1202have additional cavities contained within them. For example, the entire guide cavity1202is milled to a depth greater than 1/16 inch but less than ⅛ inch. A further reduced area within guide cavity1202is milled to a depth greater than ⅛ but less than 3/16 inch. Yet another area within the reduced area is milled to a depth greater than 3/16 inch. This allows for two reduced area cavities within the larger guide cavity1202. Guide pins908can be interchanged with varying lengths to allow for the assembled rotary power tool102, mount103, rotary tool104, adapter122and guide pin908unit to be engaged in either the full guide cavities1202or within the reduced area cavities within guide cavities1202. If a guide pin908has a length greater than zero but less than ⅛ of an inch, it would guide within the entire guide cavities1202. If a guide pin908has a length greater than ⅛ but less than 3/16 of an inch, similarly it would guide within the reduced area within the guide cavities1202. Finally, if a guide pin908has a length greater than 3/16 of an inch it would be guided within the cavity within the reduced area cavity which is within the guide cavities1202. With this arrangement, the assembled rotary power tool102, mount103, rotary tool104, adapter122and guide pins908can guide the rotary tool104to various shapes within the lower receiver by interchanging the guide pins908length.

FIG. 13depicts a method1300of jig assembly according to one or more aspects of the disclosure.

At block1302, and with reference toFIGS. 21A-B, thread the buffer adapter7into lower receiver. The buffer adapter7should sit just below surface of the lower receiver with threaded holes sitting horizontal. If the buffer adapter7is difficult to thread, #8-32 screws15can be installed for leverage.

At block1304, and with reference toFIGS. 21C-D, orient side plates3,4on each side of the lower receiver, taking note of right and left as it would be oriented in a shooting position. Insert long quick release pin10through right side plate, through receiver rear takedown, and out left side.

At block1306, and with reference toFIGS. 21E-F, place the drill guide2between side plates as shown and align screw holes. It should align only one way. Pinch side plates against drill guide and tighten four #8-32 screws15.

At block1308, and with reference toFIGS. 21G-H, use 3/16″ Allen wrench to thread ¼-20×2″ screw13through left side plate4and into right plate3using care not to cross-thread.

At block1310, and with reference toFIGS. 21I-J, align the front takedown adapter8between front takedown holes. Push the short quick release pin11through receiver and adapter as shown.

At block1312, and with reference toFIGS. 21K-L, place the guide plate1atop side plates3,4as shown. Align screw holes on guide plate1with buffer adapter7screw holes. Thread two #8-32 screws15and leave loose.

At block1314, and with reference toFIGS. 21M-N, align front takedown adapter8(not shown) with holes in guide plate1. Insert and tighten two #8-32 screws15, tightening each screw a little at time. Now, tighten two #8-32 screws15from blocks1302-1312. The buffer adapter7will self-center in buffer mount. Guide plate1may move as these are tightened. Allow guide plate to move freely during tightening.

At block1316, and with reference toFIGS. 21O-P, loosely thread six ¼-20×½″ screws14through guide plate1and into side plates3,4. Tighten screws using 3/16″ Allen wrench. The jig assembly is now complete.

FIG. 14depicts a method1400of drilling with a jig assembly according to one or more aspects of the disclosure.

At block1402, and with reference toFIG. 22A, slide ⅜″ drill stop onto shank of ⅜″ drill bit. Insert drill bit to full depth of depth gauge #21104. Place the drill stop against the edge of the guide plate1. Secure drill stop onto drill bit.

At block1404, and with reference toFIGS. 22B-C, spray WD-40 into hole #2 of the drill guide2. Insert ⅜″ drill bit into hole. Do not start drill until bit is fully inserted. Start drill and apply firm pressure. Periodically, lift drill to assist in chip removal. Reapply WD-40 as necessary. Stop drilling just before the drill stop touches the drill guide2.

At block1406, and with reference toFIGS. 22D-E, prior to drilling, ensure that jig assembly is level. Spray WD-40 into hole #3 of drill guide2. Insert 5/16″ drill bit into hole. Do not start drill until bit is fully inserted. Start drill and apply firm pressure. Periodically, lift drill to assist in chip removal. Reapply WD-40 as necessary. Stop drilling when the drill bit exits the bottom of the fire control pocket. Take care not to drill into the trigger guard. In this example, keep the drill bit perpendicular to the lower receiver. Drilling at a large angle can result in an oblong trigger slot.

At block1408, and with reference toFIGS. 22F-G, remove four #8-32 screws15and remove the drill guide2. It may be necessary to loosen the vise and/or use a screwdriver to gently pry the drill guide from between the side plates. Insert the screw driver shank into hole #2 and gently pry upward.

At block1410, and with reference toFIGS. 22H-I, remove long quick release pin10from rear takedown hole.

FIG. 15depicts a method1500of milling with a jig assembly according to one or more aspects of the disclosure.

Initially, prepare your router for milling by installing the universal router adapter5. If using a variable speed router, start router on slowest speed and gradually increase speed until optimal milling results are achieved. Generally speaking, this will equate to speed “2” to speed “4” on most variable models with “1” to “10” speed adjustments. Do not insert or remove router while it is spinning. Move router smoothly in a clockwise manner, do not mill in straight lines for extended periods. Avoid abruptly pulling the end mill or exerting excessive force to move the end mill. Apply WD-40 liberally while milling to reduce excess heat. Remove chips whenever necessary.

At block1502, and with reference toFIGS. 23A-B, install #1 (short) guide pins9on router adapter5using the two smallest socket cap screws and 7/64″ Allen wrench. Open end of pins should be facing up. Make sure pin seats are clear of debris prior to installing. Check that guide pins are properly seated.

At block1504, and with reference toFIG. 23C, set end mill depth to the first hash mark using depth gauge #11102. Set depth by holding base of router adapter5against the edge of the guide plate1. Be sure guide pins9are not between adapter and guide plate. Make sure router depth adjustment is locked when complete.

At block1506, and with reference toFIG. 23D, orient lower receiver assembly so the buffer extension is closest to the user. Place router assembly atop guide plate1, with end mill entering the earlier drilled ⅜″ hole. The notched side of the router adapter should be facing the buffer extension as shown. The guide pins should be positioned inside the guide cavities on both sides. Turn router on slowest speed and increase to operating speed once ready to mill. Mill using consistent pressure and speed, moving in a clockwise manner.

At block1508, and with reference toFIG. 23E, make the first pass of milling allowing the guide pins to follow the entire area of the guide cavities. When milling corners, gently twist the router side to side to assist to complete the entire corner radius.

At block1510, and with reference toFIG. 23F, once the entire pass has been milled to depth, set end mill depth to the second hash mark. Mill second pass following the same method and process as shown in blocks1506-1508.

At block1512, and with reference toFIGS. 23G-I, continue milling in this manner, adjusting end mill depth by 1 hash mark until you reach the final hash mark of depth gauge #1. Do not attempt to mill more than 1 hash mark, as it may result in poor quality, longer time and broken end mills.

At block1514, and with reference toFIGS. 23J-K, complete the final pass to full depth of depth gauge #1 and stop. Before continuing to depth gauge #2, the #2 (medium) guide pins9should be installed.

FIG. 16depicts a method1600of milling with a jig assembly according to one or more aspects of the disclosure.

At block1602, and with reference toFIGS. 24A-B, remove #1 (short) guide pins9and install #2 (medium) guide pins9on router adapter5reusing the (2) screws and 7/64″ allen wrench. Make sure pin seats are clear of debris prior to installing. Check that guide pins are properly seated.

At block1604, and with reference toFIG. 24C, set end mill depth to the first hash mark using depth gauge #2. Set depth by holding base of router adapter5against the edge of the guide plate1. Be sure guide pins are not between adapter and guide plate. Make sure router depth adjustment is locked when complete.

At block1606, and with reference toFIG. 24D, place router assembly atop guide plate1, with end mill entering the earlier drilled ⅜″ hole. The guide pins9should be positioned inside the #2 guide cavities on both sides. Turn router on slowest speed and increase to operating speed once ready to mill. Mill using consistent pressure and speed, moving in a clockwise manner.

At block1608, and with reference toFIG. 24E, complete the first pass allowing the guide pins9to follow the #2 guide cavities. When milling corners, gently twist the router side to side to assist to complete the entire corner radius.

At block1610, and with reference toFIG. 24F, once the entire pass has been milled, set end mill depth to the second hash mark. Mill second pass following the same method and process as outlined in blocks1606and1608.

At block1612, and with reference toFIGS. 24G-I, continue milling in the same manner, adjusting milling depth by 1 hash mark until you reach the final hash mark of depth gauge #2. Do not attempt to mill more than 1 hash mark, as it may result in poor quality, longer time and broken end mills.

At block1614, and with reference toFIGS. 24J-K, complete the final pass to full depth of depth gauge #2. Start the end mill in the 5/16″ pilot hole. Start the router at slowest speed setting and mill the hole larger before increasing the router speed. Once complete, stop. Before continuing to depth gauge #31106, the #3 (long) guide pins9should be installed on the router adapter.

FIG. 17depicts a method1700of milling with a jig assembly according to one or more aspects of the disclosure.

At block1702, and with reference toFIGS. 25A-B, remove #2 (medium) guide pins9and install #3 (long) guide pins9on router adapter5reusing the (2) screws and 7/64″ Allen wrench. Open end of pins should be facing up. Make sure pin seats are clear of debris prior to installing. Check that guide pins are properly seated.

At block1704, and with reference toFIG. 25C, set end mill depth using depth gauge #3. Set depth by holding base of router adapter5against the edge of the guide plate1. Be sure guide pins are not between adapter and guide plate. Make sure router depth adjustment is locked before when complete.

At block1706, and with reference toFIGS. 25D-E, place router on guide plate1, with end mill entering the earlier drilled 5/16″ hole. The guide pins9should be positioned inside the #3 guide cavities on both sides. Start the router at slowest speed setting and mill the hole larger before increasing the router speed. Gently mill in a clockwise manner until the trigger slot is formed.

FIG. 18depicts a method1800of drilling with a jig assembly according to one or more aspects of the disclosure.

At block1802, clamp jig assembly in the vise by the guide plate1so right side plate is facing up and ensure that the assembly is level. Use a rag or cardboard between the vise and guide plate to prevent damage to the top surface of the guide plate.

At block1804, and with reference toFIG. 26A, spray WD-40 into large hole. Insert ⅜″ drill bit into large guide hole (large left hole as shown). Do not start drill until bit is fully inserted in the guide hole. Apply moderate pressure and drill until the bit penetrates the right side wall. Do not drill through both sides.

At block1806, and with reference toFIGS. 26B-C, spray WD-40 into both small holes. Insert 19/64″ drill bit into either remaining guide holes. Do not start drill until bit is fully inserted in the guide hole. Apply moderate pressure and drill until the bit penetrates the right side wall. Do not drill through both sides. Repeat in last remaining hole.

At block1808, unclamp jig assembly from vise and flip it over so the left side plate is facing up and re-clamp by the guide plate1. Ensure that assembly is level. Use a rag or cardboard between the vise and guide plate to prevent damage to the top surface of the guide plate.

At block1810, and with reference toFIGS. 26D-E, spray WD-40 into both small holes. Insert 19/64″ drill bit into either small guide hole. Do not start drill until bit is fully inserted in the guide hole. Apply moderate pressure and drill until the bit penetrates the left side wall. Continue drilling so the bit passes through the opposite side wall connecting the holes from either side. Repeat on remaining small hole.

At block1812, and with reference toFIGS. 26F-G, spray WD-40 into large hole. Insert ⅜″ drill bit into large guide hole. Do not start drill until bit is fully inserted in the guide hole. Apply moderate pressure and drill until the bit penetrates the right side wall. Continue drilling so the bit passes through the opposite side wall connecting the holes from either side.

FIG. 19depicts a method1900of lower receiver removal using a jig assembly according to one or more aspects of the disclosure.

One advantage of the presently described jig assembly or assemblies is they do not require the user to completely disassemble the jig assembly to remove or mount an 80% lower receiver.

At block1902, and with reference toFIG. 27A, remove two #8-32 screws15from the buffer adapter7.

At block1904, and with reference toFIG. 27B, remove short quick release pin11from front takedown adapter.

At block1906, and with reference toFIG. 27C, remove ¼-20×2″ screw from left side plate4using 3/16″ Allen wrench.

At block1908, and with reference toFIG. 27D, the jig assembly and lower receiver should now be separable. For the AR-308 router jig, loosening or removing one of the side plates3,4may be employed to extract the lower receiver.

At block1910, and with reference toFIG. 27E, unthread the buffer adapter7from the lower receiver.

FIG. 20depicts various components of a jig assembly with reference toFIGS. 13-19 and 21-27, as described below:

It should be clear that the above-described jig for manufacturing a firearm lower receiver is a universal fitment and facilitates in the guidance of the rotary tool without placing the rotary tool in direct contact with any of a plurality of guidance features for firearm lower receiver manufacturing. It is straightforward to use, resists wear and produces accurate and repeatable results in the hands of both skilled and unskilled users.

The foregoing has been a detailed description of illustrative embodiments of the invention. Various modifications and additions can be made without departing from the spirit and scope if this invention. Each of the various embodiments described above may be combined with other described embodiments in order to provide multiple features. As used herein the directional terms, such as, but not limited to, “up” and “down”, “upward” and “downward”, “rear”, “rearward” and “forward”, “top” and “bottom”, “inside” and “outer”, “front” and “back”, “inner” and “outer”, “interior” and “exterior”, “downward” and “upward”, “horizontal” and “vertical” should be taken as relative conventions only, rather than absolute indications of orientation or direction with respect to a direction of the force of gravity. Furthermore, while the foregoing describes a number of separate embodiments of the apparatus and method of the present invention, what has been described herein is merely illustrative of the application of the principles of the present invention. For example, the foregoing jig can be adapted to machining and finishing other parts for a firearm, such as portions of an upper receiver that is being repaired, modified or fabricated. Moreover, the jig can be sold as part of a kit with additional right and left carriages and guide pins that are adapted for machining other firearms (for example, polishing the internal surfaces or repairing a restored firearm). This jig can be adapted for firearms of various sizes and shapes by interchanging the carriages, thereby providing a jig that can be useful to a person finishing a firearm, and repairing and/or restoring a firearm. Also, it is expressly contemplated that the size and shape of the plates of the jig can vary. In general, they are sized in an embodiment proportionally to the depiction herein relative to the size of the lower receiver. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.