WO2009067099A1

WO2009067099A1 - Magazine conversion for a semi-automatic rifle

Info

Publication number: WO2009067099A1
Application number: PCT/US2007/024288
Authority: WO
Inventors: Eric Robb; Thomas V. Seidel
Original assignee: Military Gun Supply, Inc.
Priority date: 2007-11-20
Filing date: 2007-11-21
Publication date: 2009-05-28

Abstract

Apparatus for converting a semiautomatic rifle from use of a transverse, downward-extending ammunition magazine to use of a longitudinal ammunition magazine, comprising: a bolt assembly configured for recoil blowback operation; an upper receiver section of the rifle having said bolt assembly therein, wherein said upper receiver is configured to attach to the lower receiver section of said rifle using, for example, a pivot pin and a takedown pin; and a longitudinal ammunition magazine having a transfer section disposed at a first end thereof, and attached along the upper receiver such that rounds of ammunition are dispensed from said transfer section of said longitudinal ammunition magazine into the firing chamber of said rifle.

Description

MAGAZINE CONVERSION FOR A SEMI-AUTOMATIC RIFLE

Description

Technical Field

The present invention generally relates to semiautomatic firearms and more particularly to apparatus and methods for converting an existing semiautomatic rifle such as an AR- 15/ M 16 type firearm, for use with a horizontal, top-mounted cartridge magazine and from a direct gas impingement to straight blowback mechanism.

Background Art

A well known example of a conventional semiautomatic rifle is the AR-15, also known by its military designation as the M16. The AR-15/M16 is characterized by its modular design and thus is susceptible to modifications for specific uses or with particularfeatures to enhance some operational attribute. The AR-15 modules include a lower receiver and an upper receiver assemblies. The lower receiver generally includes a housing that contains such basic components as a trigger and hammer mechanisms, a magazine well for receiving a detachable transverse magazine from below the lower receiver, and a rearward extension that houses a recoil buffer assembly. The recoil buffer assembly is in turn contained within a buttstock that is typically attached to the lower receiver. The lower receiver housing also includes a pivot pin near its forward end and a takedown pin near its rearward end for attaching the upper receiver assembly thereto and securing it in a way that the two receiver assemblies may be detached from one another rapidly and without the use of tools. To disassemble them, one merely removes the pivot and takedown pins by pressing them from the holes in the lower receiver. The upper receiver generally includes a housing that encloses such basic components as the firing chamber, bolt assembly, an extractor mechanism to extract a spent shell, a charging handle, and a mechanism for attaching the barrel assembly to the upper receiver. The upper receiver housing also includes respective holes for the pivot pin and the takedown pin. For further details of the construction of an AR-15, the reader is referred to an exploded view entitled "AR-15-Type Rifle Exploded Diagram" available at www.fulton-armorv.com. which drawing is incorporated herein by reference.

There are two types of operating mechanisms typically used in rifles, the direct gas impingement mechanism and the recoil or straight blowback mechanism. In the gas impingement, type, the expanding gases released as the cartridge is fired are routed rearward through a tube disposed above the barrel into the bolt carrier to unlock the bolt by rotating it and forcing it rearward. This action also causes the ejection of the spent cartridge shell from the side of the rifle. In the recoil type, the expanding gases push rearward directly on the bolt, causing it to move rearward and enable the ejection of the spent cartridge shell. The AR-15/M16 employs the direct gas impingement mechanism. In both types, a spring-loaded recoil buffer absorbs the recoil and then forces the bolt forward toward the chamber to secure the next round into the chamber after the round has been fed into the chamber.

In an AR-15/M16 type of semiautomatic rifle, the magazine is inserted from beneath the rifle into the magazine well that extends downward from the lower receiver portion of the rifle. When thus inserted, most of the magazine extends transversely to the longitudinal axis of the rifle, downward and outside of the well. Thus, if the magazine has a capacity of more than a dozen or so rounds, this transverse extension diminishes the compactness of the rifle making it unwieldy during use because it changes the center of gravity (i.e., the balance of the firearm) as the number of cartridges in the magazine varies, and because the magazine protrudes substantially below the rifle. An associated disadvantage of this design is that ejection of spent cartridges is out the side of the lower receiver, which increases the risk that an ejected cartridge may be ejected into an area where it could lead to injury of a person or a malfunction of nearby equipment. All three of these problems, the variable center of gravity, the compactness of the rifle, and the sideways ejection of cartridges, if solved, could substantially improve the utility and efficiency of the rifle.

In a search of the prior art, several patents disclose various ways to dispense rounds of ammunition from locations above or alongside the body of the firearm. U. S. Patent No. 2,345,003 shows an early firearm having a tube disposed along the upper side of the barrel that allows extra cartridges to be readily available for hand loading into the breech of the firearm. This early design is not a true magazine because it does not participate in reloading a next round. U. S. Patent No. 2,624,241 discloses a magazine assembly disposed alongside the barrel of a rifle that feeds a rotating transfer disk. The disk rotates under the action of an actuator when the bolt is moved rearward to receive a round from the magazine. As the bolt is moved forward when the trigger is released, the disk rotates again to align the round with the axis of the bolt and barrel and inject the round into position to be fired. U. S. Patent No. 2,773,325 illustrates a horizontal magazine assembly mounted on the top of a rifle that feeds a fresh round into the breech by the same mechanism as disclosed in the '241 patent described previously. A disadvantage of these two patents is that the rotating transfer disk mechanism is relatively complex and therefore susceptible to malfunctions such as jamming of the mechanism during operation, particularly as the parts wear or become contaminated through use, thus possibly rendering the firearm inoperable or leading to injury to persons.

One patent that attempts to solve the drawbacks of the '325 and '241 patents is U. S. Patent No. 4,336,742, which discloses a loader that dispenses cartridges from a port positioned midway between the ends of the loader to maintain the center of gravity as rounds are dispensed, and also balance the forces that move the rounds into position for insertion into the breech. However, the rounds are not dispensed in alignment with the barrel of the firearm. Another patent that addresses the jamming issue with the '241 and '325 patents is U. S. Patent No. 4,905,394 for a top mounted horizontal magazine that eliminates the rotating mechanism by providing a helical transfer ramp leading from a storage area within the magazine into the breech that dispenses a next round under spring pressure when the spent cartridge is ejected from the breech. U. S. Patent No. 5,239,911 discloses a grenade launcher having a top mounted magazine that also employs a rotating mechanism to align the next round with the barrel preparatory to launching it. However, it is also relatively complex and suffers the same disadvantage as the '325 and '241 patents.

There is thus a need to solve the problems of a stable center of gravity, compactness, sideways ejection of cartridges, and reliability of operation of the AR-15/M16 type of semiautomatic rifle. Other problems to overcome would be to provide an affordable solution that is also simple to implement. - A -

Disclosure of Invention

Accordingly, these and other problems are solved by a low cost conversion apparatus that exploits the modularity of the AR-15/M16 (hereinafter "AR-15") type of semiautomatic rifle to adapt an ammunition magazine to the AR-15 that arranges the rounds of ammunition along an axis that is essentially parallel to the longitudinal axis of the rifle instead of transverse to it thus providing a more compact, better balanced, and more maneuverable rifle. The conversion is made without altering the lower receiver module or its trigger mechanism. The resulting conversion ejects the spent cartridges downward instead of sideways for safer operation. Moreover, the conversion uses straight blowback operation instead of the direct gas impingement operation, a change that improves the reliability of the rifle.

In one embodiment an apparatus is disclosed for converting an AR-15/M 16 type or other semiautomatic rifle from use of a transverse ammunition magazine to use of a longitudinal ammunition magazine, comprising: a bolt assembly configured for recoil blowback operation; an upper receiver having a first end and an opposed second end, said upper receiver having a firing chamber along its longitudinal axis, for receiving the rifle barrel in said first end therein and said bolt assembly in said second end therein, wherein said upper receiver is configured to attach to the lower receiver and buttstock assembly of said AR-15/M16 type rifle; and a longitudinal ammunition magazine having a transfer ramp disposed at a first end thereof, said longitudinal ammunition magazine attached along said upper receiver such that rounds of ammunition are dispensed into the firing chamber from above the firing chamber.

In another embodiment a method is disclosed for converting an AR-15/M 16 type semiautomatic rifle from use of a transverse ammunition magazine to a longitudinal ammunition magazine, comprising the steps of: providing a modified bolt assembly configured for blowback operation; providing a modified upper receiver for receiving a rifle barrel in a first end therein and said modified bolt assembly in a second end therein, wherein the barrel and said bolt assembly are aligned on a common longitudinal axis; removing said upper receiver assembly, said transverse magazine, and an existing bolt assembly from the lower receiver assembly; installing a rifle barrel and said modified bolt assembly in said modified upper receiver; attaching said modified upper receiver with the rifle barrel and said modified bolt assembly to the lower receiver assembly of said AR- 15/M16 type rifle; and attaching a longitudinal magazine having a transfer ramp disposed at a first end thereof to said modified upper receiver such that said longitudinal ammunition magazine is disposed to dispense rounds of ammunition into the firing 5 chamber.

In another embodiment a semiautomatic rifle is disclosed, comprising: a standard AR- 15/M16 lower receiver assembly having its standard transverse ammunition magazine removed from a magazine well of the lower receiver assembly; an upper receiver

D assembly adapted for attaching to the lower receiver assembly via a takedown pin and a pivot pin, the upper receiver assembly further configured for straight blowback operation and ejection of spent cartridges downward through said magazine well; and a longitudinal ammunition magazine, mounted along the upper receiver assembly and configured to dispense cartridges via a transfer ramp into a firing chamber in the upper

5 receiver.

Brief Description of Drawings

Figure 1 illustrates a prior art semiautomatic rifle of the AR-15/M16 type;

D Figure 2 illustrates one embodiment of a semiautomatic rifle modified according to the present invention;

Figure 3 illustrates an exploded view of a portion of an AR-57 upper receiver assembly according to the embodiment illustrated in Figure 2; 5

Figure 4 illustrates an exploded view of a bolt assembly for use in the embodiment illustrated in Figure 3;

Figure 5 illustrates a side elevation of a section along the centerline of the assembled 3 upper receiver and bolt assembly for the embodiment of Figures 2, 3, and 4 according to the present invention; Figure 6A illustrates a side elevation of a portion of the section of Figure 5 surrounding the firing chamber, showing a fresh round of ammunition entering the firing chamber;

Figure 6B illustrates a side elevation of a portion of the section of Figure 5 surrounding the firing chamber, showing the fresh round of ammunition in position for firing;

Figure 6C illustrates a side elevation of a portion of the section of Figure 5 surrounding the firing chamber, prior to ejection of a spent round of ammunition; and

Figure 6D illustrates a side elevation of a portion of the section of Figure 5 surrounding the firing chamber, as the spent cartridge is ejected downward.

Best Mode for Carrying Out the Invention

In the following description, many of the structural components appear in more than one of the figures and are assigned the same reference numbers for convenience. Further, the embodiment described is just one alternative that illustrates the concept of the invention that combines several standard structures with several new structures to enhance the utility of the combination and advance the state of the art as compared with the prior art apparatus. In developing the structures to implement the present invention, the following problems had to be solved. (1 ) Redesign the upper receiver and the bolt assembly for straight blowback operation instead of gas impingement operation. (2) Creating a firing chamber in the upper receiver that would utilize a revised bolt assembly but the existing trigger and hammer mechanism, firing pin, etc., and would also adapt to the top-mounted longitudinal cartridge. (3) Revise the ejection mechanism to eject spent shells downward instead of out the side of the rifle. (4) Revise the position and operation of the charging handle of the standard AR-15/M16. (5) Configure the upper receiver to accept and lock to the top-mounted longitudinal magazine. (6) Revise the structure for supporting and securing the barrel to the upper receiver. (7) Coordinate the solutions to these problems to work together reliably and smoothly to realize all of the benefits of the invention. The solution to all of these problems involved changing the upper receiver and its internal parts, including the bolt assembly. The result is a novel and unobvious combination heretofore unavailable, despite the existence of a type of longitudinal ammunition magazine that could be utilized, until the insight by the present inventor, who conceived the new combination and the solutions to the above problems. As a conversion applied to one of the most popular firearms in present use, which provide a number of operational advantages, the invention is expected to meet a substantial need. While the illustrative example is described for converting an AR-15/M16 type rifle for use with the longitudinal ammunition magazine, it is readily susceptible to use on other semiautomatic or automatic firearm platforms.

Figure 1 illustrates a prior art semiautomatic rifle 10 of the AR-15/M16 type before being disassembled to modify it according to the present invention. A lower receiver assembly 12 ("lower receiver 12," or "lower receiver section 12" herein) includes a buttstock 20, a magazine well 22, a pistol grip 26, and a trigger mechanism 28. A conventional magazine 24 is inserted in the magazine well 22 and extends downward therefrom. An upper receiver assembly 14 ("upper receiver 14," or upper receiver section 14" or "upper receiver section 54" herein) includes a barrel 16, a hand guard 18 that surrounds the barrel 16, and a handle portion 30 along the top portion of the upper receiver 14. A rear sight assembly 32 is mounted at the rearward portion of the handle 30. A front sight assembly 34 is mounted atop the forward end of the hand guard 18. A flash suppressor 36 may be attached to the muzzle of the barrel 16. The upper receiver 14 is attached to the lower receiver 12 by a pivot pin 38 and a takedown pin 40, which are installed in corresponding holes through the body portions of the lower 12 and upper 14 receivers when they are assembled into position.

The modularity of the AR-15/M16 is exploited in the present invention to enable replacing the upper receiver with a different configuration that improves the functionality of the converted rifle. Use of the lower receiver of the AR-15/M16 without modification allows the use of its existing trigger and hammer mechanisms. As will be described, the upper receiver is redesigned to be compatible with the lower receiver as well as adapt a new way to dispense ammunition into the firing chamber of the rifle and a new way to eject spent cartridges from the firing chamber. Figure 2 illustrates one embodiment of a semiautomatic rifle modified according to the present invention. In brief, the modification replaces the upper receiver, barrel, bolt assembly, and magazine of the standard AR-15 with a conversion adapter called an AR- 57 in which a new rifle barrel and a modified bolt assembly are installed. More importantly, the AR-57 upper receiver is configured to receive a standard longitudinal magazine along the top portion of the AR-57. The result is a more compact, well balanced, and more maneuverable semiautomatic rifle that improves recoil performance and ejects spent cartridges downward instead of sideways. The top-mounted, longitudinal magazine employed for illustration purposes herein is a standard type manufactured by Fabrique Nationale de Herstal of Belgium. This magazine is available from authorized distributors and retailers. The magazine accommodates 5.7 * 28 mm rounds, and is fully described in U. S. Patent No. 4,905,394 issued to Predazzer, incorporated herein by reference in its entirety.

It will be appreciated that other implementations of a longitudinal magazine structure that stores the rounds of ammunition in an elongated container intended to be disposed on top of or alongside an upper receiver portion (or equivalent structure) of a semiautomatic rifle, or an automatic firearm in jurisdictions where such firearms are legal, may be used with the present invention. The rounds of ammunition may be stored transversely or longitudinally or in some other arrangement, as long as the rounds can be reliably introduced into the firing chamber in correct alignment as will be described. Moreover, the present invention is not limited to the use of the 5.7 * 28 mm ammunition, but may utilize any size or configuration or caliber ammunition consistent with the design and uses of the particular firearm that is subject to the type of conversion described and claimed herein.

Continuing with Figure 2, the new combination, designated rifle 50, includes the original lower receiver section 12 and a new upper receiver section 54, secured together with a pivot pin 38 and a takedown pin 40. Thus, the upper receiver section 54 (or, "upper receiver 54" herein) includes a pivot pin hole and a takedown pin hole, both disposed transversely through the upper receiver (see the holes 122, 124 in Figure 5) for securing the upper receiver 54 to the lower receiver 12 with a respective pivot pin 38 and a respective takedown pin 40. The pivot pin hole 122 and the takedown hole 124 are respectively disposed in the locations of the pivot pin 38 and the takedown pin 40. The pivot 38 and takedown 40 pins shown in Figure 2 are typically threadless pins that include features to retain them in position except when punched out from their respective bores with a simple tool such as a drift pin of a bullet of an unspent round of ammunition. The conversion is completed by installing the barrel 56 (perhaps with flash suppressor 36 attached) in the upper receiver 54 and by attaching the top-mounted, longitudinal magazine 64 to the upper portion of the upper receiver 54. The lower receiver includes the buttstock 20, magazine well 22, pistol grip 26, and the trigger mechanism 28. The trigger mechanism 28 includes a hammer (not shown for clarity) disposed within the lower receiver 12. Shown in phantom within the buttstock 20 is a buffer unit that includes a buffer assembly 60 and an action spring 62. The buffer unit is the same as used in a standard AR-15 in the illustrative example, but may be modified in certain other embodiments of the invention. The buffer assembly 60 is disposed in the buttstock 20 along the longitudinal axis thereof. The buffer assembly 60, 62 is preferably matched to the mass of the bolt assembly 200 (see Figure 4) and the powder charge disposed in a round of ammunition, for acting in cooperation with the bolt assembly 200 during recoil to absorb recoil forces, thus providing a more stable, comfortable weapon in use. This matching or balancing of forces may be accomplished, for example, by adjusting the mass of the buffer assembly 60 or the tension in the buffer spring 62.

The upper receiver section 54 further includes a top rear main block 70 upon which is mounted an upper scope rail 72. The top rear main block 70 encloses a release mechanism (not shown) operated by a release lever 74. The release mechanism and lever 74 enable quick removal of the longitudinal ammunition magazine 64 (or, "magazine 64" herein) as will be explained. At the forward end of the upper receiver 54 is mounted a top front magazine block 76, which may also function as a support for a scope (not shown) or a front sight (not shown). The magazine 64 includes a cylindrical transfer case 66 disposed at the rearward end (or, a "first" end) of the magazine 64 that encloses the helical, ramp-like transfer passages to guide the rounds of ammunition 152 from the magazine 64 into the firing chamber of the rifle 50, as will be described. At the forward end (or, a "second" end) of the magazine 64 is an endbell 68 for enclosing the end of the magazine 64 and providing a structure for retaining the forward end of the magazine 64 in a fixed position upon the upper receiver 54, as will be described. Figure 3 illustrates an exploded view of a portion of an AR-57 upper receiver assembly according to the embodiment illustrated in Figure 2. The AR-57 upper receiver assembly 100 replaces the original upper receiver 14 shown in Figure 1. The AR-57 upper receiver assembly 100 is completely compatible with the original lower receiver 12, and it embodies the same features as the receiver 54 shown in Figure 2 but in an exploded view to illustrate its component parts. The upper receiver 54 (upper receiver assembly 100 in Figure 3) includes a left side plate 54A and a right side plate 54B. Assembled together, with several intermediate parts, they form the body of the upper receiver 54. The intermediate parts include a barrel mount block 102 that may have a threaded bore 104 for receiving a threaded male end of the barrel 56 therein, a lower rear mount block 106, and a lower front rail block 108. These intermediate parts may be captured between the left 54A and right 54B side plates of the receiver 54 upon assembly in the relative positions shown in Figure 3. The components may be secured with pins, screws, or other fasteners, including adhesives. The barrel mount block 102 is positioned centrally, just ahead of the firing chamber portion (to be described) of the upper receiver 54. The barrel mount block 102 also includes a transverse hole 122 in a lower portion thereof for the passage of the pivot pin 38 used to secure the upper receiver 54 to the lower receiver 12. Similarly, the lower rear mount block 106 also includes a transverse hole 124 in a lower portion thereof for the passage of the takedown pin 40 used to secure the upper receiver 54 to the lower receiver 12. The several component parts of the upper receiver assembly 100 may be fabricated (cast, with secondary machining operations) from an aluminum alloy such as A356. In some embodiments, light-weight synthetic materials may be used.

Another portion of the upper receiver assembly 100 shown in Figure 3 is the top rear main block assembly formed of the top rear main block 70, an upper scope rail 72, and a release mechanism (not shown) operated by a release lever 74. The release lever 74 operates a spring-loaded magazine catch 110 that protrudes from the forward end of the block 70. The release mechanism for operating the magazine catch 110 operates the same as a door latch assembly. The magazine catch 110, instead of engaging a striker plate, engages a recess 78 (see Figures 6A through 6D) in the rear portion of the cylindrical transfer case 66 of the magazine 64. The installation of the magazine 64 in the upper receiver 54 will be described further in the description for Figure 5. Suspended from a pivot pin 120 (see Figure 5) within a machined slot cut into the underside of the forward portion of the top rear main block 70 is an ejector 118. The ejector 118 is a lever that swings downward behind the upper rim of the cartridge portion of a round of ammunition 152 (see Figure 6B) when the round 152 is present in the firing chamber 130 (see Figure 6A - 6D). The ejector 118, which may be spring loaded in some embodiments, is also shown in Figures 4, 5, and 6A - 6D.

Two other features of the upper receiver assembly 100 appear in Figure 3. In the upper edges of the left 54A and right 54B side plates, just rearward of the barrel mount block 102, the side plates are cut-out to make room for the cylindrical transfer case 66 of the longitudinal ammunition magazine 64 because the diameter of the transfer case is greater than the lateral width of the magazine 64. Thus, the surface 112 in the left side plate 54A and the surface 116 in the right side plate 54B, and the surface 114 in the forward end of the top rear main block 70 are provided, all of them cut to a radius slightly larger than the outer diameter of the cylindrical transfer case 66 of the magazine 64. Also shown in Figure 3 is a cocking handle slide 80 and cocking handle 82, secured to the cocking handle slide 80 with a screw 84. This cocking handle assembly, which slides back and forth in the elongated opening 84 cut into the side of the left side plate 54A, replaces the conventional charging handle on an AR-15/M16 type semiautomatic rifle. The cocking handle 82 is coupled to the bolt assembly 200 to enable manually moving it rearward and then forward to set a fresh round of ammunition 152 into firing position in the firing chamber 130 (see Figure 6A).

Figure 4 illustrates an exploded view of a bolt assembly for use in the embodiment illustrated in Figure 3. The bolt assembly 200 includes a rear section 202 and a front section 206, which connect together using the threaded female end 204 and the threaded male end 208. The two-section configuration permits the firing pin 210 and the firing pin spring 212 to be inserted and enclosed within a longitudinal bore formed through the bolt assembly 200. The firing pin 210 includes a reduced diameter forward end 211 that contacts the primer of the cartridge 154 (shown in Figure 6B) when the trigger 28 (shown in Figure 2) of the rifle is squeezed. The firing pin 210 also includes a head 213 against which the hammer portion of the trigger mechanism within the lower receiver 12 strikes the firing pin 210, causing the firing pin 210 to move forward to strike the primer to fire the rifle.

Suspended in a groove machined into the underside of the front section 206 of the bolt assembly 200 is an extractor 214. The extractor 214 is a spring-loaded lever having a forward end and a rearward end, and an upward-extending catch lip 215 formed at its forward end. The extractor pivots about a pivot pin 216 inserted through a transverse, horizontal hole 217 in the front section 206 of the bolt assembly 200. An extractor bias spring 220, and a damper 222 disposed within the spring 220, are positioned at the rearward end of the extractor 214 and just above it. The action of the bias spring 220 maintains the forward end of the extractor 214 in an upper position except when the bolt assembly 200 is in a forward-most position just after inserting a fresh round into the barrel (see the barrel 56 in Figure 6B) of the rifle 50. When a fresh round of ammunition 152 is dispensed into the firing chamber 130 (see Figure 6A), the lower rim of the cartridge bears downward on the forward end of the extractor 214 and engages the lip 215. After firing the rifle 50, the bolt assembly 200 moves rearward, pulling the extractor 214 and the spent cartridge 154 with it.

Several other features of the bolt assembly are shown in Figure 4. In the topside of the front section 206 of the bolt assembly 200 is a machined groove 224 that allows the ejector 118 (see Figure 3) to hang downward within the space traversed by the bolt assembly 200 as it moves forward and rearward respectively into and away from the firing chamber 130 (see Figure 6A). The groove 224 is positioned so that the ejector 118 is in position to catch the upper edge of the rim 156 of an empty (spent) cartridge (shell) 154 as it and the bolt assembly 200 move rearward during the recoil motion that occurs after firing the rifle 50. This action tilts the open end of the cartridge 154 downward, rotating the cartridge 154 down and out through the empty magazine well 22 of the lower receiver 12. Another feature of the bolt assembly 200 is the opening 226 in the rear section 202 of the bolt assembly 200 that is provided so that the hammer, which pivots within the lower receiver 12 when the trigger 28 is squeezed, can move freely upward and forward toward the head 213 of the firing pin 210. Figure 5 illustrates a side elevation of a section along the longitudinal centerline of the assembled upper receiver and bolt assembly for the embodiment of Figures 2, 3, and 4 according to the present invention. In this view along the longitudinal centerline, which is common to the barrel 56, the bolt assembly 200, the firing chamber 130, and the buffer assembly 60, the right side plate 54B of the upper receiver 54 is shown, as are sectional views of the barrel 56, top rear main block 70, upper scope rail 72, top front magazine block 76, barrel mount block 102, lower rear mount block 106, lower front rail block 108, magazine catch 110, and the rear section 202 and front section 206 of the bolt assembly 200.

Other portions of the bolt assembly 200 are shown in Figure 5 as a conventional side view to be described. The bolt assembly 200, with its component parts described in Figure 4, is shown within the upper receiver 54 and in its forward-most position but without a round of ammunition 152 in place for clarity of the structures. The firing pin 210 and the firing pin spring 212 are shown in the position they would be in just before the head 213 of the firing pin 210 would be contacted by the hammer portion of the trigger mechanism (not shown in Figure 5, but see Figure 2). The extractor 214 is shown suspended on its pivot pin 216 from the underside of the front section 206 of the bolt assembly 200. The extractor 214 is biased in the position shown, substantially parallel to the longitudinal axis of the upper receiver 54, by the action of the extractor bias spring 220. Also shown in Figure 5 is the ejector 118, suspended from its pivot pin 120, with the forward end of the ejector 118 disposed into the groove 224 in the upper side of the front section 026 of the bolt assembly 200. As mentioned herein above, the ejector 118 is a lever that swings downward behind the upper rim 156 of the cartridge portion 154 of a round of ammunition 152 (see Figure 6B) when the round of ammunition 152 is present in the firing chamber.

Figures 6A through 6D form a sequence of "snapshots" of the movement of a round of ammunition 152 from the longitudinal ammunition magazine 64 into the firing chamber 130 before firing the rifle (Figures 6A and 6B), and the movement of the spent cartridge 154 as it is extracted and ejected downward from the firing chamber 130 (6C and 6D) after firing. Many of the structural features appearing in Figures 6A through 6D have been described in conjunction with Figure 5 and will not be repeated because the Figures 6A through 6D are likewise side views along the longitudinal centerline of the upper receiver 54 and firing chamber 130. In each of the "snapshots," the bolt assembly 206 is shown in phantom to enable showing more clearly the active structures during movement of the round of ammunition 152 and the cartridge 154. Further, details of the structure and operation of the exemplary longitudinal ammunition magazine 64 are fully described and illustrated in the aforementioned U. S. Patent No.4,905,394, incorporated herein by reference in its entirety. In that reference, the path of the round of ammunition from its stored position in the magazine, which is transverse to the longitudinal axes of the magazine and the upper receiver, through its 90° rotation within the cylindrical transfer case (at the first end of the magazine) and into the firing chamber, is described. As viewed from the top side of the magazine, the rotation of the round of ammunition is clockwise (CW) into alignment with the firing chamber. The movement of the rounds within and from the magazine is caused by a spring (not shown herein, as it is clearly illustrated in the '394 patent) within the magazine.

Figure 6A illustrates a side elevation of a portion of the section of Figure 5 surrounding the firing chamber 130. The rearward portion of the longitudinal ammunition magazine 64 (also referred to herein as the "first end" of the longitudinal ammunition magazine 64) is shown cut away to illustrate the passage that the round of ammunition 152 traverses when moving from a stored position in the longitudinal ammunition magazine 64 into the firing chamber 130. The round 152, forced under the urging of a spring (not shown) within the longitudinal ammunition magazine 64 travels downward through the port 140 into the position 150, then proceeds to follow the ramp 142 toward the exit port 144, rotating into alignment with the longitudinal axis of the firing chamber 130, the barrel 56, and the upper receiver 54. Figure 6A shows a fresh round of ammunition 152 exiting the exit port 144 of the cylindrical transfer case 66, and entering the firing chamber 130 as indicated by the arrow 160. The round of ammunition 152, shown as a cartridge 154 having a rim 156 and a bullet 158 is illustrated. Further, as shown in Figure 4, the ejector 118 is in position within the groove 224, in preparation to catch the upper part of the rim 156 of the cartridge 154 as it moves rearward after the round of ammunition 152 is fired.

Figure 6B illustrates a side elevation of a portion of the section of Figure 6A surrounding the firing chamber 130, showing the fresh round of ammunition 152 in position just after bolt assembly 206 has pushed the round of ammunition 152 into the barrel 56 in position to be fired. During this motion, the extractor 214 has engaged the lower part of the rim 156 of the cartridge 154. Further, the forward end 211 of the firing pin 210 is shown in position to strike the detonator or primer of the cartridge 152 when the trigger 28 is squeezed. The bolt assembly 206 is shown moving toward the forward end of its travel as indicated by the arrow 164.

Figure 6C illustrates a side elevation of a portion of the section of Figure 6B surrounding the firing chamber, after the round of ammunition 152 is fired and during the rearward movement 166 of the empty cartridge 154 as pulled by the extractor 214 with the bolt assembly 206, just as the upper part of the rim 156 of the cartridge 154 contacts the ejector 118. All other structures shown in Figure 6C are as described in Figures 6A and 6B.

Figure 6D illustrates a side elevation of a portion of the section of Figure 6C surrounding the firing chamber 130, after the round of ammunition 152 is fired and during the downward rotation movement 162 of the empty cartridge 154 with the bolt assembly 206, just after the ejector 118 has caused the empty cartridge 154 to rotate as the lower part of the rim 156 of the empty cartridge 154 is pulled rearward by the extractor 214, and just before the momentum of the moving bolt assembly 206 that is imparted to the rotating empty cartridge 154 flings the empty cartridge 154 downward through the open magazine well 22. All other structures are as described for Figures 6A, 6B, and 6C.

The present invention is intended to be provided as a conversion assembly that includes the "AR-57" upper receiver assembly 54, the redesigned bolt assembly 200, and a redesigned barrel 56. Completing the conversion is the simple process of: (a) removing the pivot 38 and takedown 40 pins, by pressing them from the lower receiver 12 of the rifle to be converted; (b) removing the existing "transverse" magazine 24 from the rifle; (c) installing the new barrel 56 in the new upper receiver 54; (d) installing the new upper receiver 54 upon the lower receiver 12 using the pivot 38 and takedown 40 pins; and (e) installing the longitudinal ammunition magazine 64 to the top of the new upper receiver 54. Accordingly there has been described an invention that provides a low cost conversion apparatus that exploits the modularity of the AR-15/M16 type of semiautomatic rifle to adapt a longitudinal ammunition magazine to the AR-15/M16 semiautomatic rifle that arranges the rounds of ammunition along an axis that is essentially parallel to the longitudinal axis of the rifle instead of transverse to it thus providing a more compact, better balanced, and more maneuverable rifle. As development of the conversion of the present invention proceeded, the natural synergy of the longitudinal ammunition magazine, the modified bolt assembly, ejector and extractor mechanisms, and the upper receiver assembly that enabled these components to work together reliably and smoothly, became apparent. This natural synergy was unexpected, and not only adapted the longitudinal ammunition magazine to a popular semiautomatic rifle to solve the problems discussed herein above, but produced a rifle in which the result exceeded the sum of the parts. Further, the conversion is made without altering the lower receiver module or its trigger and hammer mechanism. The resulting conversion ejects the spent cartridges downward instead of sideways for safer operation. Moreover, the conversion uses straight blowback operation instead of the direct gas impingement operation, a change that improves the reliability of the rifle. Tests have shown the recoil forces are lighter and the action can be operated with less cycle time without sacrificing reliability or accuracy.

While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof. Some of these alternatives have been suggested herein above, while others within the scope of the appended claims will occur to persons skilled in the art.

Claims

What is claimed is:

5 1. Apparatus adapted to be used in conjunction with an AR-15/M16 type semiautomatic rifle having a rifle barrel and a buttstock aligned along a longitudinal axis thereof and a lower receiver, said apparatus for converting the rifle from use of a transverse ammunition magazine to use of a longitudinal ammunition magazine, comprising: a bolt assembly configured for recoil blowback operation;

) an upper receiver having a first end and an opposed second end, said upper receiver having a firing chamber along the longitudinal axis, for receiving the rifle barrel in said first end therein and said bolt assembly in said second end therein, wherein said upper receiver is configured to attach to the lower receiver of said AR-15/M16 type rifle; and

5 a longitudinal ammunition magazine having a transfer ramp disposed at a first end thereof, said longitudinal ammunition magazine attached along said upper receiver such that rounds of ammunition are dispensed into the firing chamber from above the firing chamber.

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2. The apparatus of Claim 1 , wherein said bolt assembly includes a firing pin and an extractor for extracting a spent cartridge from the firing chamber of the AR-15/M16.

3. The apparatus of Claim 1 , wherein said upper receiver further comprises: a pivot pin hole and a takedown pin hole, both disposed transversely through said 5 upper receiver for securing said upper receiver to the lower receiver with a respective pivot pin and a respective takedown pin.

4. The apparatus of Claim 3, wherein the transfer ramp in said longitudinal ammunition magazine is disposed above the firing chamber in position to dispense a round of

D ammunition from the transfer ramp of said longitudinal ammunition magazine into the firing chamber upon ejection of a spent cartridge.

5. The apparatus of Claim 3, wherein said longitudinal ammunition magazine is secured to said upper receiver by first and second pawl members extending from corresponding portions of said upper receiver and engaging respective forward and rearward ends of said longitudinal ammunition magazine.

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6. The apparatus of Claim 5, wherein at least one of said first and second pawl members pivots under spring tension to releasably secure said longitudinal ammunition magazine to said upper receiver.

D 7. The apparatus of Claim 1 , wherein said upper receiver includes an ejector for acting in cooperation with said bolt assembly as it recoils after firing to eject a spent cartridge downward through an open magazine well of said AR-15/M16.

8. The apparatus of Claim 1 , further comprising:

5 a buffer assembly to be disposed in the buttstock along said longitudinal axis and matched to a mass of the bolt assembly and a powder charge disposed in a round of ammunition, for acting in cooperation with said bolt assembly during recoil.

9. Apparatus adapted to be used in conjunction with an AR-15/M16 type semiautomatic D rifle having a rifle barrel and a buttstock aligned along a longitudinal axis thereof, said apparatus for converting the rifle from use of a transverse ammunition magazine to use of a longitudinal ammunition magazine, comprising: an upper receiver, having a firing chamber along the longitudinal axis, for receiving the rifle barrel in a first end therein and a bolt assembly in a second end therein, wherein 5 said upper receiver is configured to attach to a lower receiver and buttstock assembly of said AR-15/M16 type rifle; a bolt assembly configured for recoil blowback operation wherein said bolt assembly includes a firing pin and an extractor for extracting a spent cartridge from the firing chamber of said upper receiver; D a first and a second transverse hole in said upper receiver disposed in respective positions to enable securing said upper receiver to a lower receiver of the AR-15/M16 type rifle using an existing pivot pin and a takedown pin associated with the lower receiver; an ejector disposed in said upper receiver for acting in cooperation with said bolt assembly as it recoils after firing to eject a spent cartridge downward through an open magazine well of said AR-15/M16 type rifle; and a longitudinal ammunition magazine having a transfer ramp disposed at a first end 5 thereof, said magazine attached along said upper receiver such that rounds of ammunition are dispensed into the firing chamber from above the firing chamber.

10. The apparatus of Claim 9, wherein said longitudinal ammunition magazine is secured to said upper receiver by first and second pawl members extending from corresponding

D portions of said upper receiver and engaging respective forward and rearward ends of said longitudinal ammunition magazine.

11. The apparatus of Claim 10, wherein at least one of said first and second pawl members pivots under spring tension to releasably secure said longitudinal ammunition

5 magazine to said upper receiver.

12. The apparatus of Claim 9, wherein the lower receiver and buttstock assembly includes a spring-loaded buffer housed within the buttstock along the longitudinal axis for acting in cooperation with said bolt assembly during recoil.

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13. A method for converting an AR-15/M16 type semiautomatic rifle, having a lower receiver assembly, an upper receiver assembly, and a rifle barrel and buttstock aligned along a common longitudinal axis thereof, from use of a transverse ammunition magazine to a longitudinal ammunition magazine, comprising the steps of:

5 providing a modified bolt assembly configured for blowback operation; providing a modified upper receiver for receiving a rifle barrel in a first end therein and said modified bolt assembly in a second end therein, wherein the barrel and said bolt assembly are aligned on the common longitudinal axis; removing said upper receiver assembly, the transverse magazine, and an existing 3 bolt assembly from the lower receiver assembly; installing a rifle barrel and said modified bolt assembly in said modified upper receiver; attaching said modified upper receiver with the rifle barrel and said modified bolt assembly to said lower receiver assembly of said AR-15/M16 type rifle; and attaching a longitudinal ammunition magazine having a transfer ramp disposed at a first end thereof to said modified upper receiver such that said longitudinal 5 ammunition magazine is disposed to dispense rounds of ammunition into a firing chamber disposed within said modified upper receiver.

14. Apparatus adapted to be used in conjunction with a semiautomatic rifle having a rifle barrel and a buttstock aligned along a longitudinal axis thereof, and a lower receiver

) section, said apparatus for converting the rifle from use of a transverse ammunition magazine to use of a longitudinal ammunition magazine, comprising: a bolt assembly configured for recoil blowback operation; an upper receiver section having a first end and an opposed second end, said upper receiver section having a firing chamber along the longitudinal axis, for receiving 5 the rifle barrel in said first end therein and said bolt assembly in said second end therein, wherein said upper receiver section is configured to attach to the lower receiver section and buttstock assembly of said rifle; and a longitudinal ammunition magazine having a transfer ramp disposed at a first end thereof, said longitudinal ammunition magazine attached along said upper receiver such 3 that rounds of ammunition are dispensed into the firing chamber from above the firing chamber.

15. The apparatus of Claim 14, wherein said bolt assembly includes a firing pin and an extractor for extracting a spent cartridge from the firing chamber.

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16. The apparatus of Claim 14, wherein said upper receiver section attaches to the lower receiver section using an existing pivot pin and a takedown pin associated with the lower receiver section.

3 17. The apparatus of Claim 16, wherein said transfer ramp in said longitudinal ammunition magazine is disposed above the firing chamber in position to dispense a round of ammunition from said cartridge transfer ramp of said longitudinal ammunition magazine into the firing chamber upon ejection of a spent cartridge.

18. The apparatus of Claim 16, wherein said longitudinal ammunition magazine is secured to said upper receiver section by first and second pawl members extending from corresponding portions of said upper receiver section and engaging respective forward and rearward ends of said longitudinal ammunition magazine.

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19. The apparatus of Claim 18, wherein at least one of said first and second pawl members pivots under spring tension to releasably secure said longitudinal ammunition magazine to said upper receiver section.

) 20. The apparatus of Claim 14, wherein said upper receiver section includes an ejector for acting in cooperation with said bolt assembly as it recoils after firing to eject a spent cartridge downward through an open magazine well of said semiautomatic rifle.

21. The apparatus of Claim 14, wherein the lower receiver section and buttstock 5 assembly includes a spring-loaded buffer housed within the buttstock along the longitudinal axis for acting in cooperation with said bolt assembly during recoil.

22. A semiautomatic rifle, comprising: a standard AR-15/M16 lower receiver assembly having its standard transverse ) ammunition magazine removed from a magazine well of the lower receiver assembly; an upper receiver assembly adapted for attaching to the lower receiver assembly via a takedown pin and a pivot pin, said upper receiver assembly further configured for straight blowback operation and ejection of spent cartridges downward through the magazine well; and

> a longitudinal ammunition magazine, mounted along said upper receiver assembly and configured to dispense cartridges via a transfer ramp into a firing chamber in said upper receiver.

23. The rifle of Claim 22, said upper receiver assembly further comprising: ) a rifle barrel installed in said upper receiver assembly; and a bolt assembly configured for straight blowback operation and having an ejector for ejecting said spent cartridges downward through the magazine well; wherein the barrel and said bolt assembly are aligned along a common longitudinal axis of said upper receiver assembly.

24. The rifle of Claim 23, said bolt assembly further comprising:

> an extractor for extracting a spent cartridge to a position to be ejected from said upper receiver assembly by the ejector as said bolt assembly moves rearward during recoil.

25. The rifle of Claim 23, wherein said longitudinal ammunition magazine is mounted ) along the top of said upper receiver assembly in parallel alignment with the longitudinal axis of said upper receiver assembly.