POLYMER FIREARM MAGAZINE WIDTH RETENTION SYSTEM

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority to U.S. Provisional Application No. 63/708,399 filed Oct. 17, 2024, which is incorporated herein by reference in its entirety.

BACKGROUND

The present invention generally relates to firearms, and more particularly to ammunition magazines detachably mountable to firearms for holding and dispensing a stack of cartridges.

Ammunition magazines for firearms are designed to conveniently store and feed multiple rounds of shells or cartridges. Such magazines have a spring feed mechanism which automatically dispenses the cartridges into the firearm for firing and are used in many different types of firearms, including rifles (including carbines with shortened barrels), and pistols. One type of magazine used is a box style magazine, which may be removably detached to the firearm action. These magazines hold a plurality of stacked cartridges. When the action is cycled and the spent shell or cartridge casing is extracted from the chamber and ejected, a fresh cartridge is automatically moved by the spring mechanism into the breech area of the firearm from which the movable bolt or breech block loads the cartridge into the chamber of the barrel for firing.

Most pistol magazine bodies utilize metal material in order to retain shape when loaded with cartridges. Polymer has long been viewed as inferior due to its mechanical properties and how it performs over time. In addition, polymers are more susceptible to environmental factors and conditions unlike metals such as temperature. Users are therefore willing to pay a premium for an all metal magazine in order to achieve the reliability they require for dispensing cartridges and locking the magazine to the firearm. As material advances are made throughout the firearm industry, new polymer resins are being developed to make polymer a more suitable material for this application. However, depending on the magazine design, the softer polymer material still has the tendency to deform, flex, and lose shape when cartridges are loaded thereby resulting in a bulge in the body typically at the midsection between the top and bottom ends of the magazine depending on how many rounds (cartridges) are inserted inside the magazine body.

More specifically, as one non-limiting example, when a .22LR cartridge magazine is not in a single-stack configuration but instead a staggered double stack, the more rounds that are forced into the magazine body the more force/load is presented laterally outward on the sidewalls in the direction of the width of the magazine thereby causing bulging. A double stack magazine holds cartridges in two staggered zigzag vertical columns to provide a high capacity magazine. When this happens, functional issues arise and the magazine no longer performs as it should leading to inability to seat and latch the magazine into the magazine well of the firearm and/or cartridge feed jams thereby adversely affecting the inability to automatically dispense cartridges into the breech area of the firearm when attempting to fire the firearm. One known solution is to load less than the full number of cartridges into the magazine that it can hold to avoid the magazine body bulging issue thereby unfortunately underutilizing and sacrificing magazine capacity. The extent of the problem varies depending on the type of ammunition used.

Improvements in polymer ammunition magazines for firearms are needed to avoid the foregoing problem and reliably dispense cartridge without jams.

SUMMARY

The present disclosure provides a polymer magazine width retention system comprising in one embodiment a shape retention device that avoids the foregoing magazine body bulging problem described above. In one embodiment, the shape retention device is preferably a metallic shape retention clip detachably mounted to the portion of the magazine body most prone to lateral bulging such at the midsection which loses dimension and parallel alignment of the sidewalls when fully loaded to capacity with ammunition cartridges. The midsection covers a vertical portion or area between top and bottom ends of the magazine having a defined height and thus does not refer to simply the midpoint therebetween which is subsumed within the midsection. The midsection is located within the double stack section of the magazine in one embodiment. The retention clip may be U-shaped in some preferred embodiments; however, other configurations of clips may be used such as continuous annular metal rings or bands affixed to the magazine body.

The magazine shape retention clip may be detachably or permanently coupled to the exterior surface of the magazine body. In one embodiment, the clip includes latching features which mate with complementary configured latching features on the exterior surface of the magazine body to detachably coupled and retain the clip without the need for separate fasteners. The mating latching features may be male and female in configuration in one embodiment. In other embodiments, the retention clip may be permanently coupled to the magazine body such as via an overmolding processes known in the art in which the polymer body is overmolded onto the metallic clip making the clip an integral and inseparable permanent part of the molded magazine body.

The metallic shape retention clip according to the present disclosure aids in maintaining the shape and dimensions (e.g., width) of a polymeric magazine body when fully loaded. In addition to adding structural rigidity and reinforcement to the softer polymer magazine body at the location most susceptible to bulging, the metallic retention clip also prevents the user from attempting to over-fill the magazine with cartridges as is common with polymer-only magazines by retaining the original undeformed magazine body shape and dimensions. The shape retention clip which structurally reinforces the midsection of the magazine body according to principles of the present disclosure advantageously allows the use of lower cost polymers to construct the body in contrast to use of available higher priced specialty reinforced polymers. In one embodiment, the magazine may be a staggered double stack high capacity magazine (e.g., 20 rounds or more); however, smaller capacity magazines also prone to the magazine body bulging problem will find application of the present invention beneficial. In a double stack magazine, ammunition cartridges are stored in a vertical staggered stack arrangement as noted above in which adjacent cartridges in each stack are vertically spaced apart and laterally offset from cartridges in the other stack with respect to the vertical centerline of the magazine. Such magazines include a lower double stack section, and an upper single stack section closest to the top of the magazine in which the double stack of cartridges converges into a single stack for feeding into the firearm. A transition section is formed between the double and single stack sections, and located closer towards the top end of the magazine to maximum the vertical extent of the double stack section to maximize cartridge capacity. In one non-limiting embodiment, for example, the cartridges may be .22 LR rimfire cartridges the magazine may have a capacity of 20 rounds or more; however, other types and calibers of cartridges including centerfire cartridges and other double stack magazine capacities may be used with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the exemplary embodiments will be described with reference to the following drawings where like elements are labeled similarly, and in which:

FIG. 1 is a top rear perspective view of a firearm high-capacity magazine according to the present disclosure with polymer body and magazine shape retention device;

FIG. 2 is a front top perspective view thereof;

FIG. 3 is a bottom rear perspective view thereof;

FIG. 4 is a bottom front perspective view thereof;

FIG. 5 is a side perspective view thereof;

FIG. 6 is an enlarged detail taken from FIG. 5;

FIG. 7 is an exploded side perspective view of the magazine showing the shape retention device removed from the magazine;

FIG. 8 is an enlarged detail taken from FIG. 7;

FIG. 9 is an exploded perspective view of the magazine;

FIG. 10 is a front view thereof;

FIG. 11 is a rear view thereof;

FIG. 12 is a first side view thereof;

FIG. 13 is a second side view thereof;

FIG. 14 is a top view thereof;

FIG. 15 is a bottom view thereof;

FIG. 16 is a vertical side cross-sectional view thereof;

FIG. 17 is a horizontal transverse cross-sectional view thereof taken through the shape retention device;

FIG. 18 is a vertical rear cross-sectional view taken from FIG. 17;

FIG. 19 is a side cross-sectional view of the magazine showing ammunition cartridges loaded into the magazine;

FIG. 20 is a horizontal transverse cross-sectional view of the magazine taken through the shape retention device and showing ammunition cartridges loaded into the magazine;

FIG. 21 is a vertical rear cross-sectional view of the magazine taken through the shape retention device and showing ammunition cartridges loaded into the magazine; and

FIG. 22 is a top front perspective view of an alternative embodiment of the magazine showing a metal feed lip insert coupled to the top end of the polymer magazine body.

All drawings are schematic and not necessarily to scale. Parts given a reference numerical designation in one figure may be considered to be the same parts where they appear in other figures without a numerical designation for brevity unless specifically labeled with a different part number and/or described otherwise herein.

DETAILED DESCRIPTION

The features and benefits of the invention are illustrated and described herein by reference to exemplary (“example”) embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features.

In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

The terms “shell,” “round,” and “cartridge” may be used interchangeably herein in reference to describing ammunition, and therefore should not be construed as limiting the invention or the claims appended hereto. For convenience and brevity, further description of ammunition which follows will generally use the non-limiting term of “cartridge.”

As used throughout, any ranges disclosed herein are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, any references which may be cited herein are all hereby incorporated by reference in their entireties. In the event of a conflict in a definition or meaning of a term in the present disclosure and that of a cited reference, the present disclosure controls.

For convenience of description and not limitation, the non-limiting illustrated embodiment disclosed depicts the present magazine used with a stack of .22 LR rimfire rimmed cartridges. However, the magazine may be used with rimmed centerfire cartridges in other embodiments (e.g., .357 magnum .38 special cartridge, .45 Colt, etc.). Accordingly, the present invention is not necessarily limited to use with rimfire cartridges alone in which the primer is located in the crushable rim of the cartridge.

The term “rimmed” cartridge is used in its conventional sense in the art to connote a cartridge having a radially protruding rim at bottom that forms a flange with a diameter greater than the diameter of the cartridge case at the base of the cartridge. ‘Semi-rimmed’ cartridges are considered functionally identical to ‘rimmed’ cartridges as the former have a rim that is greater in diameter than the case at the rim, but to a lesser degree than ‘rimmed’ cartridges. “Rimless” cartridges are a type of cartridge in which the rim has the same diameter as the cartridge case so that the rim does not protrude outwards beyond the case unlike rimmed or semi-rimmed cartridges. The present magazine with magazine shape retention device may be used with any of the above cartridge types.

FIGS. 1-22 depict a detachable polymeric magazine 20 for a firearm and features thereof according to the present disclosure including a magazine shape retention device 100 previously noted herein. Magazine 20 may be used with any type of magazine fed firearm including long guns (e.g., rifles, carbines, etc.) or handguns (e.g., pistols, etc.) which utilize a detachable box magazine for storage and dispensing of rimmed, semi-rimmed, or rimless ammunition cartridges. The type of autoloading loading firearm does not limit the scope or applicability of the invention.

The present magazine may be used with various types of cartridges which may cause to the sidewall bulging problems described above when loading the magazine.

Examples of such cartridges include for example without limitation rimfire cartridges (e.g., .22 LR rimmed cartridges) and centerfire cartridges (e.g., .357 magnum .38 special cartridge, .45 Colt, etc.). In one non-limiting embodiment as illustrated for convenience of description, the cartridges may be .22 LR rimmed rimfire cartridges. Accordingly, magazine 20 is not limited for use with any single type cartridge.

Magazine 20 is a box-type magazine which generally comprises a hollow and elongated open tubular magazine body 21 (also referred to as a magazine tube or housing in the art) that defines an internal cavity 22 configured for holding a plurality of cartridges 30 in a vertically stacked arrangement. Cavity 22 extends for the full interior height of the magazine body.

In some embodiments, magazine 21 is configured to have a capacity for holding and dispensing greater than 10 ammunition cartridges, which is a common maximum capacity of standard magazines for pistols. In one representative non-limiting embodiment, magazine 21 may have a 20 cartridge or more capacity for holding .22LR rimmed cartridges. In order to package more than 10 cartridges into the magazine while retaining the same general length as a standard magazine, the tubular body of the magazine 20 includes a lower double stack section 90 configured to hold a vertically staggered double stack of the cartridges 30 therein, and an upper single stack section 91 configured to gradually converge the double cartridge stack together so as to form a generally single stack of cartridges for dispensing a single cartridge at a time into the breech area of the firearm each time the action is automatically or manually cycled (see, e.g., FIG. 21). The term “vertically staggered” connotes that the centerline CC of each cartridge (extending through the projectile and the base thereof shown in FIG. 19) in the stack is laterally offset from the centerline of the adjacent cartridges and centerline CL of the magazine.

The upper portions of the sidewalls 27 in single stack section 101 are non-parallel and angled with respect to each other (i.e. non-parallel) being inclined inwards towards vertical reference plane VP and centerline CL of the magazine (see, e.g., FIG. 21). Transition section 92 is formed between lower double stack section 90 and upper single stack section 91 at the point where the sidewalls begin to angle inwards into cavity 22 of the magazine such that there is insufficient lateral room or space to maintain a double stack of cartridges. The transition section converges the double stack of magazines into a single stack for chambering. Lower double stack section 90 has a larger lateral width than the top end 23 of magazine 20. Upper single stack section 91 may have a generally frustoconical shape when viewed from front to rear, or vice-versa (see, e.g., FIG. 21).

Cartridges 30 in the lower double stack section 90 as shown are positioned in vertically offset or staggered side to side relationship. There are no two cartridges in direct side to side relationship in which the centers of the cartridges lie in the same horizontal plane in the lower double stack section 90 (see, e.g., FIG. 21).

The lateral sidewalls 27 of tubular magazine body 21 in lower double stack section 91 may be parallel relative to each other. Sidewalls 27 in upper single stack section 101 however are sloped inwards relative to each other and converge moving upwards towards the open top end 23 of the magazine having a width configured to dispense just a single cartridge one at a time into the breech area of firearm via the spring-biased cartridge feed mechanism further described elsewhere herein. The point at which the top of the parallel sidewalls 27 of the lower double stack section begin to converge and angle towards each other defines the transition section 92 in the magazine body between the lower double stack section and the upper single stack section (see, e.g., FIG. 21).

With continuing general reference to FIGS. 1-22 as applicable, the tubular magazine body 21 of the magazine 20 is elongated in both the vertical direction (top to bottom) and the horizontal front to rear direction (more so in the vertical direction as is typical for most box type magazines). For convenience of reference and not limitation, the body 21 defines a vertical centerline VC extending through the top and bottom of the magazine and a horizontal axis HA extending through the front and rear walls of the magazine (see, e.g., FIG. 17). Centerline VC and axis HA each intersect and extend through the geometric center of the magazine. Magazine 20 defines vertical reference plane VP extending front to rear which contains vertical centerline VC and horizontal axis HA. Axis HA defines an axial direction sometime referred to herein between the front and rear walls of the magazine.

The tubular magazine body 21 comprises a partially open top end 23, open bottom end 24, front wall 25, rear wall 26, and pair of opposing laterally spaced apart sidewalls 27 extending therebetween along the longitudinal axis LA. The walls 25-27 extend vertically in the direction of vertical centerline VC of magazine 20 and are arranged orthogonally to each other as shown forming a generally rectangular cuboid magazine body structure. Rear wall 26 defines exterior rear surface 26, front wall 25 defines exterior front surface 25A, and exterior side surfaces 27A are defined by each sidewall 27 of the magazine body. Collectively these surfaces form exterior surfaces of the magazine.

The magazine tube or body 21 may be formed of a suitable preferably lightweight non-metallic material such as without limitation polymer (e.g. polycarbonates, nylon) or polymer based composites (e.g. particle or fiber reinforced polymers such as glass filled nylon, carbon fiber filled polymer, etc.). In one preferred but non-limiting embodiments, the material may be carbon fiber and glass filled TPU (thermoplastic polyurethane). Other reinforced or unreinforced polymeric materials suitable for constructing a magazine may be used.

The top end 23 of the magazine is substantially open to magazine cavity 22 to dispense cartridges therefrom and includes a pair of inwardly extending (e.g., angled or curved) cartridge feed lips 28 which engage and retain the uppermost cartridge 30 in the stack. This prevents the column or stack of cartridge from being vertically ejected from the top of the magazine by the cartridge spring feed mechanism further described herein. The feed lips also position the top cartridge at the desired presentation angle for proper feeding into the breech and chamber, and are space laterally apart to provide a longitudinal passage therebetween for the bolt or slide to enter and strip the uppermost round (cartridge) in the stack out of the magazine when the firearm action is cycled. In one embodiment, the feed lips 28 may be configured and positioned to engage the generally straight portion of cartridge case 31 lying between the projectile 34 (e.g., bullet or slug) at front and rear base 32 of the cartridge 30. Accordingly, the cartridge feed lips 28 may be longitudinally offset towards and located in the rear half 21B of the magazine 20 such that the lips do not extend into the front half 21A of the magazine which holds the projectile end of the cartridges 30 in the stack. This provides clearance to the top cartridge in the spring-biased stack to be dispensed and stripped from the magazine by the action (e.g., bolt or breech face of a slide) when cycled.

The cartridge feed lips 28 may be an integral unitary part of the monolithic polymeric magazine body 21 formed at the top end 23 thereof (see, e.g., FIG. 1). In this embodiment, the feed lips are formed of polymer being part of the same single piece polymer magazine body. Because the feed lips undergo higher wear when repeatedly discharging a cartridge from the stack in the magazine, it is sometimes desirable in certain embodiments to form the feed lips of metal to obtain higher wear resistance and increase magazine life. FIG. 22 shows an alternative embodiment of a magazine 20′ comprising a metal feed lip insert 140 comprising metal feed lips 28′ which is detachably or permanently coupled to the top end 23 of the polymeric magazine body thereby forming a hybrid magazine body. Any suitable method commonly used in the art to couple magazine components or parts together may be used to couple feed lip insert 140 to magazine body 21. FIG. 22 shows the use of coupling pins 141 as one non-limiting example. The remaining parts and associated components of the magazine 20′ are the same as magazine 20 described elsewhere herein including the use of the metallic shape retention clip 110 coupled to the midsection of the magazine. Although the feed lip insert may be formed of metal, it is located too high on the magazine to be effective in preventing bulging of the midsection of the polymer magazine body.

Referring now to FIG. 19, rimmed cartridges 30 usable magazine 20 or 20′ in one embodiment each include a cartridge base 32 (“case head”) at one end, projectile 34 (e.g., bullet or slug) at the opposite end, and annular generally cylindrical cartridge case 31 extending between the ends. A radially protruding annular rim 33 is formed at the base end of case 31 having a diameter larger than the adjoining base end of the case. The rimmed cartridge 30 may be a rimfire or a centerfire cartridge in various embodiments. In other embodiments, a semi-rimmed or rimless cartridges arranged in double stack magazine 20 may be used with a magazine shape retention device according to the present disclosure.

The laterally spaced apart feed lips 28 extend axially (i.e. in the general direction of horizontal axis HA) from a point proximate the rear wall 26 and terminate at a point spaced apart rearward from the front wall 25 by a sufficient horizontal distance to allow the cartridges to be axially dispensed from or inserted into the magazine 20 beneath the feed lips from the front half 21a of the magazine. In one embodiment, the feed lips may not extend farther than midway between the front and rear walls 25, 26 of the magazine.

In one embodiment, the magazine 20 may be configured for detachable mounting and insertion into a downwardly and upwardly open magazine well of a firearm from the underside (bottom) of the firearm. In one embodiment, the magazine includes a latching feature 20A (see, e.g., FIG. 8) which is configured to engage a convention spring-biased magazine latch positioned in the frame of the firearm adjacent the magazine well for detachably mounting the magazine to the firearm. The latch mechanism locks the magazine in position for use and releases/drops the magazine via operation of the release button of the mechanism for exchanging magazines 20. Such magazine latch mechanisms including other variations and their operation are well known in the art without undue elaboration. Examples of various types of latch mechanisms are shown in commonly-owned U.S. Pat. No. 9,194,637, which is incorporated herein by reference in its entirety.

With continuing general reference to FIGS. 1-22 as applicable, magazine 20 further includes an internal cartridge spring feed mechanism. The spring mechanism is disposed in the cavity 22 of the magazine. The feed mechanism may include an axially (e.g., horizontally) elongated follower 60, magazine spring 40, and spring base 80 which is secured to bottom end of the magazine tube or body 21 by detachable floor plate 50. The spring biases the follower and stack of cartridges supported thereon upwards towards the open top end 23 of the magazine. The top end 41 of spring 40 engages the underside or bottom surface of the follower 60 via a spring locating boss (see, e.g., FIG. 9). The bottom end 42 of the spring engages the spring base 80 via a spring locating boss 80A. The spring bosses are complementary configured to the shape of the spring to retain the spring in its proper orientation and position.

In one embodiment, the magazine spring 40 may be a cylindrical helical or coil compression spring with circular shaped coils as shown in the non-limiting illustrated embodiment. The coils each define a diameter, and spring 40 may be a straight coil spring as shown. In alternative embodiments, square or rectangular cross-sectional wire profiles may be used instead of circular. Spring 40 may be formed of suitable spring steel wire. In some embodiments, the spring 40 may be a constant force spring as shown; however, variable force springs may also be used. The type of spring used does not limit the invention.

Spring 40 extends vertically and defines a spring axis SA which may be axially spaced apart and offset from centerline CL of magazine 20 by an axial distance OD (see, e.g. FIG. 16). Spring 40 may be offset towards and located proximate to front wall 25 of the magazine body 21. Accordingly, the spring may be located directly beneath the open portion of the top end 23 of the magazine forward of the feed lips 28. This offset positioning of spring 40 allows the spring to actively bias the spring follower 60 upwards into a position with the spring force acting directly on the underside of the front portion of the follower. This advantageously contributes positive dispensing and feeding of the cartridges 30 from the magazine into the breech area of the firearm with the front tip or bullet of the cartridge angled upwards at the required angle for smooth chambering (see, e.g., FIG. 20). An analogous arrangement is shown in commonly-owned U.S. Pat. No. 11,493,293, which is incorporated herein by reference in its entirety.

The follower 60 shown unassembled from the rest of the magazine in FIG. 9 may be axially elongated in the direction of and aligned with the horizontal axis HA of the magazine when mounted therein. In front to rear length, the follower extends axially from the front wall 25 to rear wall 26 of the tubular magazine body 21 (see, e.g., FIG. 16). Follower 60 is slideably moveable downwards and upwards in cavity 22 of the magazine 20 for loading cartridges 30 into or dispensing cartridges from the magazine. The follower defines a rear portion 60B and a vertically elongated front portion 60C extending downwardly from the front of the rear portion. Viewed another way, front portion 60C may be considered to be cantilevered from the rear portion 60B forming an L-shaped follower. Front portion 60C therefore has a greater vertical height than the height of the rear portion 60B.

Follower 60 includes a front end 61, rear end 62, top 63, bottom 64, and pair of opposed sides 65 extending from front to rear. The top 63 of follower 60 in one embodiment defines a pair of adjacent cartridge feed surfaces 66, 67 configured to support the cartridges 30 in the stack (see, e.g., FIGS. 19 and 21). Each cartridge feed surface supports the lowermost cartridge in one of the two staggered vertical stacks of cartridges while cartridges remain in the lower double stack section of the magazine. Cartridge feed surface 66 may be arcuately curved and feed surface 67 may be flat in one embodiment as shown. The feed surfaces are sloped downward moving front to rear to ensure that the uppermost cartridge in the stack is presented with its tip (e.g., projectile) angled upwards for proper and reliable feeding from the magazine into the breech area of the firearm. As cartridges are dispensed from the magazine, magazine spring 40 expands and moves the follower and stack of cartridges upwards in the magazine in a conventional manner. Other suitable configurations of cartridge feed surfaces may be used depending on the type of cartridges loaded in the magazine.

Follower 60 may be a non-rotating design in one embodiment. This means that the follower does not rotate forward/rearward in vertical reference plane VP or twist laterally about the vertical centerline CL of the magazine when sliding vertically upwards in the magazine 20 to dispense cartridges at the desired presentation angle to the bolt for chambering when the action is cycled. Accordingly, the follower 60 and tubular magazine body 21 of magazine 20 may be cooperatively configured to smoothly guide travel of the follower upwards/downwards in the magazine while preventing vertical rotation or lateral twisting of the follower relative to the magazine body 21. This prevents rotation of the follower inside cavity 22 of the tubular magazine body 21 in the vertical reference plane VP to counteract the unbalanced biasing force imparted to the front portion of follower 60 by the off-center placement of magazine spring 40 in the front half of the magazine as described elsewhere herein. Advantageously, this avoids potential follower and cartridge feed jams, thereby providing smooth movement of the follower in the magazine.

Referring to FIGS. 9 and 14, magazine body 21 includes a pair of inwardly extending guide protrusions 69 formed in the top portion of the front half 21A of the magazine on each lateral sidewall 27. Protrusions 69 extend in opposite lateral directions inwards into magazine cavity 22. Follower 60 defines a pair of outwardly open clearance channels 70 which interact with the guide protrusions. The follower needs clearance in order to finish its upward travel as guide ribs inside the magazine (not shown) converge into the single-feed area. The channels and protrusions also help prevent rotation of the follower relative to the magazine at top of the magazine.

To facilitate loading cartridges into magazine 20, follower 60 may include a laterally and outwardly open loading through passage 130 configured to receive and engage a shaft of a commercially available cartridge loading tool (e.g., speed loaders or magazine loaders) such as a load assist button. Such tools are known in the art and used to draw the follower downward against the resistance created by biasing force of the magazine spring 40 thereby making it easier to load the cartridges. Each sidewall 27 of the magazine includes a vertical tool slot 131 to allow the shaft of the tool to access and engage the loading through passage 130 of the follower.

Floor plate 50 of magazine 20 will now be further described. The floor plate has a body that is axially elongated in the direction of the horizontal axis HA. In longitudinal length, floor plate 50 in one non-limiting embodiment may extend from a point rearward of rear wall 26 of the tubular magazine body 21 to a point forward from the front wall 25 of the magazine body resulting in a forward and rearward projection therefrom (see, e.g., FIG. 16). In transverse or lateral width, floor plate 50 extends beyond both sidewalls 27 of the tubular magazine body 21 (see, e.g., FIG. 21). The floor plate defines an upward and rearwardly open receptacle 51 configured to receive the bottom end 24 of the tubular magazine body 21 and spring base 80 therein when assembled together.

Floor plate 50 may be detachably coupled to the tubular magazine body via any suitable method. As one non-limiting example, floor plate 50 may be slideably and detachably coupled to the bottom end of the tubular magazine body 21. Referring to FIGS. 9, 16, and 21, a pair of opposing inwardly facing and open mounting grooves 53 are formed within receptacle 51 of floor plate 50 which extend for a length in the front to rear direction. Grooves 53 slideably receive a pair of outwardly turned mounting flanges 54 formed on the bottom end 24 of the tubular magazine body 21 to couple the floor plate to the magazine. The front wall 57 of the floor plate defines a travel stop that engages front wall 25 of the tubular magazine body 21 to fix the proper front to rear mounting position of the floor plate on the body.

To retain the spring base 80 in proper position on the floor plate 50, the spring base includes a downwardly extending mounting protrusion 56 which is received in a complementary configured mounting hole 55 formed in the bottom wall 57 of the floor plate at the bottom of receptacle 51. In one embodiment, both the mounting protrusion and hole may be round. When the magazine body 21 is slid onto the floor plate 50 for assembly, the mounting protrusion 56 will snap into and enter the mounting hole 55. The downward biasing force of spring 40 will retain the protrusion in place and further serves to lock the floor plate to the magazine body. Removal of the floor plate 50 requires a tool to be inserted through hole 55 from below the floor plate to depress the mounting protrusion upwards thereby allowing the magazine body to slide rearwards to uncouple from the floor plate.

The magazine shape retention device 100 for preventing bulging of a polymer staggered double stack magazine according to the present disclosure will now be described in further detail. Reference is made in general to FIGS. 1-22 as applicable, and in particular FIGS. 8-9 which show the device 100 in isolation and greater detail.

In one preferred but non-limiting embodiment, magazine shape retention device 100 may be in the form of a metallic shape retention clip 110 having a U-shaped body 111 configured for coupling to exterior surfaces of the magazine. Retention clip 110 comprises a laterally extending clip rear wall 114 which engages the rear wall 26 of the magazine body 21, and a pair of clip sidewalls 115 each engaging one of the lateral sidewalls 27 of the magazine body. Clip sidewalls 115 are each oriented perpendicularly to clip rear wall 114 and spaced laterally apart to define an open reception space 117 therebetween which receives the magazine body therein when the clip is mounted to the magazine 20 (see, e.g., FIG. 1). Clip 110 is therefore upwardly, downwardly, and forwardly open in one embodiment for entry of the magazine body into the space 117. The clip 110 is configured to slideably engage the magazine body 21 when coupled thereto as further described herein.

Shape retention clip 110 is configured for mounting to the double stack section and preferably the midsection M of the magazine body 21 where the magazine width bulging problem is most acute with high capacity polymer magazines when filled to capacity with ammunition cartridges. In one embodiment, the magazine body 21 may include a mounting recess 120 at midsection M which is complementary configured to the shape of retention clip 110. The mounting recess 120 is contiguous in extent and formed in the rear wall 26 and adjoining portions of each sidewalls 27 of the magazine body to receive the U-shaped body of the clip. Exposed outer surfaces of retention clip 110 are recessed substantially flush with the exterior rear and side surfaces 26A and 27A of the magazine body in one embodiment when the retention clip is seated in the mounting recess to retain external dimensions of the magazine which prevents the magazine from binding on surfaces or structures within the magazine well of the firearm when the magazine is inserted or withdrawn from the firearm (see, e.g., FIGS. 1 and 17). The top edges 112 and bottom edges 113 of the clip each collectively formed by clip rear wall 114 and clip sidewalls 115 thus do not protrude outwards from the magazine body by an appreciable distance via the flush mount which might snag surfaces or features in the magazine well. The clip mounting recess 120 of the magazine has a height which is just slightly larger than the clip so that the clip can be tightly nested in the recess as shown such that there are no substantial portion of the recess not filled by the clip.

When mounted to the magazine body 21, the top edge 112 of the shape retention clip 110 is spaced downwards from the top end 23 of the magazine body, and the bottom edge 113 of the clip is spaced upwards from the bottom end 24 of the magazine body. This confines the vertical extent or height H1 of the clip (identified in FIG. 8) in a preferred embodiment to where it is needed at the midsection M of the magazine for the purpose of preventing the magazine dimensional bulging issue when cartridges are loaded into the magazine. Shape retention clip 110 therefore has a height substantially less than the height of the magazine body 21. In other possible embodiments depending on the design of the magazine issue, the clip 110 may extend farther upwards and/or downwards from the midsection as need to ensure all portions of the magazine body subject to bulging are structurally reinforced by the clip.

The shape retention clip 110 has a horizontal length L1 (front-to-rear) which does not cover or interfere with the vertical tool slot 131 in the magazine body 21 to allow the shaft of a magazine loading tool to access and engage the loading through passage 130 of the follower 60 described elsewhere herein (see, e.g., FIGS. 9 and 12).

In a preferred but non-limiting embodiment, the body 111 of shape retention clip 110 is formed of a metal which is elastically deformable (i.e. elastic memory) to allow the clip to be expanded when detachably coupled to the magazine body 21 and then return to its original shape via a snap fit without the need for threaded or other type mechanical fasteners. Accordingly, clip 110 in one embodiment may be formed of a suitable elastically deformable ductile sheet metal which will not plastically deform when the clip is installed and can spring back to original shape after full installation or if removed from the magazine entirely. The clip sidewalls 115 in particular are elastically deformable between an undeformed inward position substantially perpendicular to the clip rear wall 114 and a deformed outward position obliquely angled to the clip rear wall. In the outward position, the sidewalls 115 are spread farther apart from each other than in the inward position. In one embodiment, clip 110 may have a body 111 with a one-piece monolithic body structure which is bent to the U-shape as shown. This provides an economical fabrication technique for the clip. A non-limiting example of a metal usable for the clip 110 is medium-carbon steel such as without limitation AISI 1050 steel having a carbon content of about 0.50%; however, other suitable elastically deformable metals (steel or non-steel) may be used.

To facilitate the snap fit coupling, the retention clip includes a pair of first coupling features 116 configured to lockingly engage mating second coupling features 118 formed on the magazine body 21. In one embodiment, coupling features 116 may comprise mounting holes 116 formed in the clip sidewalls 115. Holes 116 may be vertically elongated in one embodiment as shown. At least one mounting hole is provided in each sidewall 115. The second coupling features 118 may comprise mounting protrusions 118 formed on each sidewall 27 of the magazine body. Protrusions 118 may be complementary configured to holes 116 and therefore may be vertically elongated in one embodiment as shown. At least one mounting protrusion is formed in each sidewall 27. The mounting protrusions coincide in shape, location and number to the shape, location and number of the mounting holes provided in the shape retention clip 110 so as to form a mutual locking relationship when the clip is mounted to the magazine to secure the clip to the magazine. Locking protrusions 118 are thus formed within the mounting recess 120 of the magazine body when a recess is provided which is preferable but not necessarily required in all embodiments depending on the configuration of the magazine.

To assemble the shape retention clip 110 to the magazine 20, the clip is slid forward onto the magazine body 21 over the rear wall 26 of the magazine and into the mounting recess 120. When the front edge 119 of each clip sidewall 115 encounters and slideably engages the laterally projecting mounting protrusions 118, the sidewalls deform and bend outwards in opposing direction with respect to clip rear wall 114 into a temporary slightly splayed shape. As the clip continues to be slid forward, the mounting protrusions 118 on the magazine will eventually enter and snap into mounting holes 116 on the clip as the splayed clip sidewalls 115 resiliently return inwards to their original configuration to lock the clip to the magazine via a snap fit. The clip 110 cannot be withdrawn and removed from the magazine while the mounting protrusions 118 are seated in the mounting holes 116. To remove the clip, the clip sidewalls 115 must each be spread back outwards via a suitable pry tool to disengage the mounting protrusions from the mounting holes.

In other embodiments, it bears noting that the reverse arrangement of locking features may be used in which mounting holes may instead be formed in the magazine body within mounting recess 120 and mounting protrusions may formed in each clip sidewall 115 which extend inwardly toward each other into reception space 117 of the clip. Other configurations of mutually engageable mounting features may be used on the shape retention clip and magazine so long as a locking engagement is formed therebetween to couple the clip to the magazine. In other less preferred but acceptable embodiments, threaded fasteners with heads recessed into countersunk threaded holes in the magazine body be used to detachably couple the clip 110 to the magazine 20.

In alternative embodiments, the polymer magazine body 21 may be overmolded in a conventional manner onto the metallic shape retention clip 110 to form a permanent inseparable coupling between the clip and magazine. Preferably, the clip remains in the same external position on the exterior of the magazine to avoid interfering with the cartridge feeding operation of the magazine. The clip may have the same configuration as previously described herein. The mounting holes 116 of the clip and the mounting protrusions 118 on the magazine may be omitted or kept to further secure the bond between the clip and magazine as polymer will fill the mounting holes when injection molded.

In yet other possible embodiments, the mounting holes 116 of the clip and the mounting protrusions 118 on the magazine could be omitted by permanently coupling the clip to the magazine via a suitable industrial adhesive.

Other possible ways to detachably or permanently couple the shape retention clip 110 to the magazine 20 may be used in other embodiments.

In operation, a user loads cartridges into the internal cavity 22 of the magazine body 21 through the top end 23 until the stack of cartridges extends from the upper single stack section at least partially down into the lower double stack section of the magazine. The shape retention clip 110 provides a resistance force onto the magazine body (e.g., sidewalls 27) opposing outward acting forces thereon created by loading the cartridges into the double stack section. The shape retention clip prevents outward bulging of the magazine body (e.g., sidewalls) at the midsection M which lies in the double stack section of the magazine in one embodiment.

Example Embodiments

The following is a list of example embodiments and various combinations of features of the invention according to the present disclosure.

Embodiment 1. A double stack magazine for a firearm comprising: a tubular magazine body formed of polymer, the magazine body defining a vertical centerline and an internal cavity configured to hold a stack of cartridges, the magazine body including an at least partially open top end for dispensing cartridges, a bottom end, a front wall, a rear wall, and opposed lateral sidewalls extending between the front and rear walls; the magazine body including a lower double stack section configured to hold a vertical staggered double stack of the cartridges, and an upper single stack section; a magazine spring disposed in the cavity; a follower moveably disposed in the cavity and biased in an upwards direction towards the top end of the magazine body by the magazine spring, the follower configured to support and dispense cartridges in the stack from the magazine; a metallic shape retention device coupled to a midsection of the magazine body between the top and bottom ends, the retention device configured and arranged to restrain the magazine body from bulging at the midsection when cartridges are loaded into the magazine.

Embodiment 2. The magazine according to Embodiment 1, wherein the midsection of the magazine body is located in the double stack section.

Embodiment 3. The magazine according to Embodiment 1 or 2, wherein the shape retention device is an elastically deformable shape retention clip detachably coupled to exterior surfaces of the magazine body at the midsection.

Embodiment 4. The magazine according to Embodiment 3, wherein the shape retention device comprises a top edge which is spaced downwards from the top end of the magazine body, and a bottom edge spaced upwards from the bottom end of the magazine body.

Embodiment 5. The magazine according to Embodiment 4, wherein the retention clip is U-shaped.

Embodiment 6. The magazine according to Embodiment 5, wherein the retention clip comprises a laterally extending clip rear wall engaging the rear wall of the magazine body, and a pair of clip sidewalls each engaging one of the lateral sidewalls of the magazine body.

Embodiment 7. The magazine according to Embodiment 6, wherein the retention clip is seated in a complementary configured mounting recess formed in the rear wall and each of the sidewalls of the magazine body.

Embodiment 8. The magazine according to Embodiment 7, wherein outer surfaces of retention clip are substantially flush with the exterior surfaces of the magazine body when the retention clip is seated in the mounting recess to retain external dimensions of the magazine body.

Embodiment 9. The magazine according to any one of Embodiments 4-8, wherein the retention clip is formed of elastically deformable steel sheet metal.

Embodiment 10. The magazine according to any one of Embodiments 4-9, wherein the retention clip includes a pair of first coupling features configured to lockingly engage mating second coupling features on the magazine body via a snap fit to detachably couple the retention clip to the magazine body.

Embodiment 11. The magazine according to Embodiment 3, wherein the magazine further comprises a pair of cartridge feed lips disposed at the top end of the magazine body to retain an uppermost cartridge in the stack in the magazine.

Embodiment 12. The magazine according to Embodiment 11, wherein the feed lips are part of a metal feed lip insert coupled to the top end of the magazine body.

Embodiment 13. The magazine according to Embodiment 11, wherein the feed lips are an integral unitary part of the magazine body.

Embodiment 14. The magazine according to any one of Embodiments 4-13, wherein each of the lateral sidewalls of the magazine body includes a vertical tool slot configured for insertion of a cartridge loading tool to access the follower, wherein the retention clip has a horizontal length which does not cover the tool slot when the retention clip is coupled to the magazine.

Embodiment 15. The magazine according to any one of Embodiments 1-14, wherein the magazine spring is a circular coil compression spring which is horizontally offset from the vertical centerline of the magazine body towards the front wall of the magazine body.

Embodiment 16. The magazine according to Embodiment 2, wherein the retention clip comprises a U-shaped body disposed on exterior surfaces of the magazine body at the midsection.

Embodiment 17. The magazine according to Embodiment 16, wherein the magazine body is overmolded onto the retention clip to permanently couple the retention clip to the magazine body.

Embodiment 18. The magazine according to Embodiment 17, wherein the retention clip comprises a laterally extending clip rear wall disposed on the rear wall of the magazine body, and a pair of clip sidewalls each disposed on one of the lateral sidewalls of the magazine body.

Embodiment 19. The magazine according to Embodiment 18, wherein the retention clip is detachably coupled to the magazine body and substantially flush with portions of the magazine body adjacent to top and bottom edges of the retention clip.

Embodiment 20. A double stack magazine for a firearm comprising: a tubular magazine body formed of polymer, the magazine body defining a vertical centerline and an internal cavity configured to hold a stack of cartridges, the magazine body including an at least partially open top end for dispensing cartridges, a bottom end, a front wall, a rear wall, and opposed lateral sidewalls extending between the front and rear walls; the magazine body including a lower double stack section configured to hold a vertical staggered double stack of the cartridges, an upper single stack section, and a transition section formed between the double stack section and the single stack section; a magazine spring disposed in the cavity; a follower moveably disposed in the cavity and biased in an upwards direction towards the top end of the magazine body by the magazine spring, the follower configured to support and dispense cartridges in the stack from the magazine; a U-shaped metallic retention clip coupled to the rear wall and both sidewalls of the magazine body at a midsection of the magazine body between the top and bottom ends, the retention clip configured and arranged to restrain the magazine body from bulging in a lateral direction at the midsection when cartridges are loaded into the magazine.

Embodiment 21. The magazine according to Embodiment 20, wherein the retention clip is spaced apart from the top and bottom ends of the magazine body.

Embodiment 22. The magazine according to Embodiment 21, wherein the retention clip comprises a laterally extending clip rear wall engaging the rear wall of the magazine body, and a pair of clip sidewalls each engaging one of the lateral sidewalls of the magazine body.

Embodiment 23. The magazine according to Embodiment 22, wherein the clip sidewalls are elastically deformable between an undeformed inward position perpendicular to the clip rear wall and a deformed outward position obliquely angled to the clip rear wall.

Embodiment 24. A method for preventing bulging of a double stack ammunition magazine for a firearm, the method comprising: providing or having the magazine which includes a polymer magazine body, a partially open top end, a bottom end, and an internal cavity comprising a lower double stack section and an upper single stack section; installing a spring-biased follower in the internal cavity operable to dispense cartridges from the magazine; coupling a metal magazine shape retention clip to a midsection of the magazine body before or after installing the spring-biased follower; and loading cartridges into the internal cavity onto the spring-biased follower until a stack of cartridges extends from the upper single stack section at least partially down into the lower double stack section of the magazine; the shape retention clip providing a resistance force onto the magazine body opposing outward acting forces thereon created by loading the cartridges into the double stack section, the shape retention clip preventing outward bulging of the magazine body at the midsection.

While the foregoing description and drawings represent exemplary embodiments of the present disclosure, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made within the scope of the present disclosure. One skilled in the art will further appreciate that the embodiments may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the disclosure, which are particularly adapted to specific environments and operative requirements without departing from the principles described herein. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive. The appended claims should be construed broadly, to include other variants and embodiments of the disclosure, which may be made by those skilled in the art without departing from the scope and range of equivalents.