Semiautomatic Rifle with Downward Ejection
A bolt assembly for a rifle is configured for recoil blowback operation and cooperation with a round of ammunition dispensed from a magazine into a firing chamber of the rifle. An extractor disposed in a lower, forward portion of the bolt assembly and an ejector disposed in an upper, forward portion of the bolt assembly further cooperate with the round of ammunition to extract a spent cartridge of the round of ammunition from the firing chamber and eject the spent cartridge downward from the firing chamber.
The present U.S. patent application is a Continuation-In-Part of U.S. patent application Ser. No. 11/943,385 entitled “MAGAZINE CONVERSION FOR A SEMI-AUTOMATIC RIFLE,” filed Nov. 20, 2007.
BACKGROUND OF THE INVENTIONThe 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/M16 type firearm, for use with a horizontal, top-mounted cartridge magazine and from a direct gas impingement to straight blowback mechanism.
Background of the Invention and Description of the Prior ArtA 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 particular features 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-armory.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. Pat. 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. Pat. 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. Pat. 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. Pat. 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. Pat. 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. Pat. 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.
SUMMARY OF THE INVENTIONAccordingly, 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/M16 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/M16 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 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 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 receiver.
A bolt assembly for a rifle configured for recoil blowback operation is disclosed, comprising a body having a first section for cooperating with a round of ammunition dispensed into a firing chamber of the rifle from a magazine; an extractor disposed in a lower, forward portion of the first section; and an ejector disposed in an upper, forward portion of the first section. The extractor and ejector cooperate with the round of ammunition to extract a spent cartridge of the round of ammunition from the firing chamber and eject the spent cartridge downward from the firing chamber.
In another aspect of the present invention, a bolt assembly for an upper receiver of an AR-15 type rifle configured for ejecting spent cartridges downward through a magazine well of the rifle is disclosed, comprising a bolt assembly having first and second guide rail tracks formed along respective first and second sides of the bolt assembly; an extractor disposed at least partially within a lower, forward end of the bolt assembly; and an ejector disposed at least partially within an upper, forward end of the bolt assembly and operative in cooperation with the extractor to eject the spent cartridge downward through the magazine well of said AR-15 type rifle when the rifle is fired.
In yet another aspect of the present invention, a semiautomatic rifle is disclosed, comprising a lower receiver assembly for a standard AR-15—type rifle having a magazine well disposed in its underside; an upper receiver assembly adapted for attaching to the lower receiver assembly and configured for ejection of spent cartridges downward through the magazine well of the lower receiver assembly; and an ammunition magazine detachably mounted upon the upper receiver assembly and configured to dispense cartridges into a firing chamber of the upper receiver.
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.
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 anew way to dispense ammunition into the firing chamber of the rifle and a new way to eject spent cartridges from the firing chamber.
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
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.
Another portion of the upper receiver assembly 100 shown in
Suspended from a pivot pin 120 (see
Two other features of the upper receiver assembly 100 appear in
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
Several other features of the bolt assembly are shown in
Other portions of the bolt assembly 200 are shown in
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.
In an alternate embodiment of the present invention, a modified bolt assembly 400 is illustrated in
Referring to
Continuing with
The bolt assembly 400 shown in part in the exploded view in
Referring to
The extractor and ejector mechanisms are illustrated in cross section in
Continuing with
Referring to
While the invention has been shown in only a few of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof. The embodiments described herein above include modifications to the upper receiver section of an AR-15—type semi-automatic rifle to adapt the upper receiver to accept the mounting of an ammunition magazine thereon, thus facilitating a more compact rifle and more efficient, reliable dispensing of rounds of ammunition into the firing chamber of the rifle. The modifications include redesign of the bolt assembly in the upper receiver to provide for direct, downward ejection of the cartridges through the existing magazine well after firing the rifle. The existing magazine well provides an open channel for free passage of the spent cartridges downward toward the ground because the standard AR-15—type magazine is no longer used. It will also be appreciated by persons skilled in the art that several other structural components are no longer required, thus simplifying the maintenance and operation of the rifle and improving its reliability. These unnecessary components include the standard gas tube, charging handle and bolt carrier for the AR-15 type rifle.
With regard to the magazine 64 illustrated in
Claims
1. A bolt assembly for a rifle configured for recoil blowback operation, comprising:
- a body having a first section for cooperating with a round of ammunition dispensed into a firing chamber of said rifle from a magazine;
- an extractor disposed in a lower, forward portion of said first section; and
- an ejector disposed in an upper, forward portion of said first section.
2. The apparatus of claim 1, wherein:
- said extractor and said ejector cooperate with said round of ammunition to extract a spent cartridge of said round of ammunition from said firing chamber and eject said spent cartridge downward from said firing chamber.
3. The apparatus of claim 1, wherein:
- said body includes a second section attached to said first section at an end opposite said forward portion of said first section.
4. The apparatus of claim 3, wherein:
- said first and second portions of said body of said bolt assembly include first and second guide rail tracks formed along respective first and second sides of said bolt assembly.
5. The apparatus of claim 4, wherein:
- said first and second guide rail tracks of said bolt assembly slide along corresponding guide rails disposed on each internal side of a recoil bore aligned with a barrel of said rifle.
6. The apparatus of claim 1, wherein said extractor comprises:
- a pivoting lever urged by a first spring to grasp a rim of said cartridge when said bolt assembly is in a forward-most position within said rifle.
7. The apparatus of claim 1, wherein said ejector comprises:
- a piston urged by a second spring to force said cartridge downward when said cartridge is fully extracted from a barrel of said rifle.
8. A bolt assembly for an upper receiver of an AR-15 type rifle configured for ejecting spent cartridges downward through a magazine well of said rifle, comprising:
- a bolt assembly having first and second guide rail tracks formed along respective first and second sides of said bolt assembly;
- an extractor disposed at least partially within a lower, forward end of said bolt assembly; and
- an ejector disposed at least partially within an upper, forward end of said bolt assembly and operative in cooperation with said extractor to eject said spent cartridge downward through said magazine well of said AR-15 type rifle when said rifle is fired.
9. The apparatus of claim 8, wherein said bolt assembly comprises:
- a bolt assembly configured for recoil blowback operation.
10. The apparatus of claim 9, said bolt assembly further comprising:
- a forward section and a second section, coupled together and including first and second guide rail tracks formed along respective first and second sides of said bolt assembly.
11. The apparatus of claim 10, wherein:
- said first and second guide rail tracks slide along corresponding first and second guide rails disposed on each internal side of a recoil bore aligned with a barrel of said rifle.
12. The apparatus of claim 8, wherein said extractor comprises:
- a pivoting lever urged by a first spring to grasp a rim of said cartridge when said bolt assembly is in a forward-most position within said rifle.
13. The apparatus of claim 8, wherein said ejector comprises:
- a piston urged by a second spring to force said cartridge downward when said cartridge is fully extracted from a barrel of said rifle.
14. A semiautomatic rifle, comprising:
- a lower receiver assembly for a standard AR-15—type rifle having a magazine well disposed in its underside;
- an upper receiver assembly adapted for attaching to said lower receiver assembly and configured for ejection of spent cartridges downward through said magazine well of said lower receiver assembly; and
- an ammunition magazine detachably mounted upon said upper receiver assembly and configured to dispense cartridges into a firing chamber of said upper receiver.
15. The apparatus of claim 14, said upper receiver comprising:
- a bolt assembly installed in said upper receiver assembly and configured for straight/recoil blowback operation and having an ejector for ejecting said spent cartridge downward through said magazine well.
16. The apparatus of claim 15, said bolt assembly further comprising:
- an extractor for extracting a spent cartridge to a position to be ejected from said upper receiver assembly by said ejector as said bolt assembly moves rearward during recoil.
17. The apparatus of claim 15, said upper receiver comprising:
- a rifle barrel installed in said upper receiver assembly;
- wherein said rifle barrel and said bolt assembly are aligned along a common longitudinal axis of said upper receiver assembly.
18. The apparatus of claim 14, wherein:
- said ammunition magazine is mounted on top of said upper receiver assembly for dispensing said cartridges into said firing chamber.
19. The apparatus of claim 14, wherein further:
- said upper receiver includes no bolt carrier, no charging handle, and no gas tube.
Type: Application
Filed: Apr 1, 2010
Publication Date: Jul 14, 2011
Inventors: Eric P. Robb (Arlington, TX), Ronald R. Royce (Woodinville, WA)
Application Number: 12/752,623
International Classification: F41A 3/54 (20060101); F41A 3/12 (20060101); F41A 9/61 (20060101); F41A 15/00 (20060101);