Patent Publication Number: US-2009223103-A1

Title: Cartridge magazine with shoulder retention features

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 12/190,401 filed Aug. 12, 2008 and entitled “Firearm Stock Features,” which is a utility of U.S. Provisional Patent Application Ser. No. 61/025,242 filed Jan. 31, 2008, which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. The Field of the Invention 
     The present application generally relates to firearms and magazines for firearms. In particular this application discusses magazines. 
     2. The Relevant Technology 
     Modern firearms make use of cartridges that include a projectile seated in a casing. The casing has an internal cavity defined therein that contains a charge of rapidly combusting powder. A primer is seated in a recess formed in a rear portion of the casing. A hole in the primer casing places the primer in communication with the internal cavity containing the powder. A projectile is seated in the front portion of the casing such that the powder is more or less sealingly contained in the casing between the primer and the projectile. 
     An action, such as a bolt action, is used to advance the cartridge into a firing chamber ahead of firing. While in the firing chamber, a firing pin strikes the primer, causing the primer to ignite. The ignition is directed to the powder, which burns within the casing. The powder burns within the casing generates a rapidly expanding gas. The pressure generated by the rapidly expanding gas propels the projectile from the casing and through the barrel of the firearm. The action can then be cycled to remove the empty casing. Cycling the action includes withdrawing the action from the firing chamber to extract a cartridge, and then advancing the action to position another cartridge within the firing chamber. 
     Often a magazine holds additional cartridges such that as the cartridge is advanced toward the firing chamber, an additional cartridge is automatically fed into the firing chamber. Such a configuration can allow for relatively rapid feeding of cartridges. A feed rate can be further enhanced through the use of a detachable magazine, some times referred to as a clip. The clip often includes a body that is sized to receive several cartridges. A spring and follower are positioned within the body that maintain the top cartridge in such a position that when the clip is attached to the firearm advancing the action feeds a cartridge into the firing chamber as discussed above. 
     The range and accuracy with which a firearm shoots the projectile can depend on a number of factors. Accuracy is often measured by the area over which projectiles impact a target. Factors that affect accuracy can include, among others, variable forces on the barrel, variations of the position of cartridges relative to the firing chamber and/or relative to the barrel, variations in the powder charge, the seating force between the projectile and the casing, and the orientation and position of the projectile relative to the casing. To maximize range, relatively large charges of powder are used to propel relatively heavy projectiles. 
     In order to maximize accuracy, especially with cartridges for long range shooting, variation is minimized from cartridge to cartridge and from shot to shot. One approach is to use cartridges loaded in a carefully controlled manner. By reducing variation and using large powder charges and heavy projectiles, accurate shots of more than 1,000 yards are possible. While providing for accuracy at long ranges, the recoil associated with large powder charges and heavy projectiles generates significant recoil can be significant. 
     Often, the recoil can be sufficiently violent to cause the front of the magazine to impact the tip of any projectiles in the magazine. Accordingly, to ensure accuracy at long ranges, cartridges are single fed into the firing chamber instead of using a magazine. While such an approach can eliminate contact between a cartridge and the magazine, and thus eliminate impact of the magazine with the tip of the projections, single feeding cartridges can increase the possibility that the shooter will drop a cartridge and thereby negate many of the processes used to maintain consistency. Further, single feeding can be time consuming and tedious. 
     The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some examples described herein may be practiced. 
     BRIEF SUMMARY OF THE INVENTION 
     A magazine configured to receive a plurality of cartridges includes a front portion, a rear portion, and opposing lateral portions between the front portion and the rear portion, the opposing lateral portions including a neck portion, a shoulder portion adjacent the neck portion, and a base portion adjacent the shoulder portion, wherein a width of the neck portion adjacent the shoulder portion has a width that is about 0.005 inches to about 0.04 inches or more greater than the nominal size of a neck portion of the cartridges. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential characteristics of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates a perspective view of a firearm according to one example; and 
         FIGS. 2A-2D  illustrates a detachable magazine according to one example. 
     
    
    
     Together with the following description, the Figures demonstrate and explain the principles of a magazine configured to reduce jamming and/or protect a tip of a projectile. In the Figures, the thickness and configuration of components may be exaggerated for clarity. The same reference numerals in different Figures represent similar, though necessarily identical, components. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Magazines, firearms, and methods of manufacture are provided herein that allow multiple cartridges to be loaded into a magazine. The magazines include a front wall, a rear wall, and opposing lateral portions between the front wall and the rear wall. The lateral portions include a neck portion adjacent the front wall that is configured interact with cartridges to prevent a tip of the cartridge from impacting the front wall as the firearm to which the magazine is attached recoils. For example, a relatively small clearance can be provided between a neck portion of the magazine and a corresponding neck portion of a casing. The relatively small clearance can help retain a shoulder portion of the casing during recoil to help prevent the shoulder of the casing from jamming in the neck portion of the magazine. Accordingly, the magazine can include a shoulder retention feature. Such a configuration can allow successive cartridges to fed from the magazine while maintaining the interface between the cartridge&#39;s casing and projectile, thereby maintaining consistency. Accordingly, such a configuration can allow for relatively rapid shots while maintaining accuracy. 
       FIG. 1  illustrates a firearm  100  that includes a stock  105 , a barrel  110 , an action  115 , and a magazine  120 . The action  115  is operatively associated with the barrel  110 . In the illustrated example, a bolt-type action is shown. It will be appreciated that in other examples, other types of actions, such as pump-type actions, recoil-operated actions, gas-operated actions, as well as any other type of actions can be operatively associated with any types of actions. 
     Regardless of the type, cycling of the action  115  moves a cartridge into position to be fired and removes the casing after the cartridge has been fired. For example, forward operation of the action  115  can move a cartridge through a breech  125  and into position with the barrel  115 . Thereafter, a trigger (not shown) can be actuated to release a firing pin in the action  115 . The firing pin strikes a primer, which ignites gun powder in a casing to propel a projectile through the barrel  110 . 
     Rearward operation of the action extracts the spent casing and moves the action  115  rearward of the magazine  120 . The magazine  120  is coupled to the stock  105  and is operatively associated with the action  120  and/or the breech  125  in such a manner that forward operation of the action moves a cartridge from the magazine  120  into position with the barrel  115 . The process can then be repeated until the rounds in the magazine  120  are complete. 
     Thereafter, additional cartridges can be fed into the magazine  120 . In one example, cartridges can be fed through the breech  125  into the magazine  120 . In other examples, the magazine  120  can be a detachable magazine. In such a configuration, cartridges can be fed either through the breech  125  or the magazine  120  that can be detached from the stock  105 . For ease of reference, a detachable magazine will be described below. It will be appreciated that a permanently secured magazine can also be described. 
       FIGS. 2A-2D  illustrate a detachable magazine  200  with shoulder retention features according to one example. In the example illustrated in  FIGS. 2A-2D , the magazine  200  generally includes a front portion  205 , opposing lateral portions  210 ,  215 , a rear portion  220 , and a base plate  225 . The front portion  205 , the opposing lateral portions  210 ,  215 , and the rear portion  220  define a recess configured to receive a cartridge of a specified type. The detachable magazine  200  can be configured to receive any type of cartridge, including, without limitation, .243 Winchester, .308 Winchester, .300 Winchester Magnum, or .338 Lapua Magnum caliber cartridges, represented schematically as cartridge  230  in  FIG. 2B  having a casing  235  and a projectile  240 . As will be discussed in more detail below, the detachable magazine  200  is configured to engage and support the casing  235  in such a manner to reduce or eliminate contact between the projectile  240  and the front portion  205  of the detachable magazine during recoil and further help retain the shoulder of the casing relative to the magazine. 
     In particular, as illustrated in  FIG. 2C  when viewed from above the opposing lateral portions  210 ,  215  have a contour that generally parallels the profile of a cartridge  230  of the type the magazine is configured to house (shown in dashed lines). Accordingly, the lateral portions  210 ,  215  form a neck portion  245 A, a shoulder portion  250 A, and a base portion  255 A that correspond with a neck portion  245 B a shoulder portion  250 B, and a base portion  255 B of the casing  230  respectively. A clearance can be selected between the neck portion  245 A of the magazine and the neck portion  245 B of the casing  230  that retains the shoulder portion  250 B of the casing  230  to prevent the shoulder portion  250 B from jamming with the magazine  200  during recoil or other forces. Such a functionality can be referred to as a shoulder retention feature. 
     In addition to defining a profile corresponding to the profile of the cartridge  230 , the lateral portions  210  define a cavity configured to receive the cartridge  230 . As illustrated in  FIG. 2A , part of the upper ends of the opposing lateral portions  210 ,  215  can be configured as lips  260 ,  265  that extend upwardly and inwardly from the opposing lateral portions  210 ,  215 . The detachable magazine  200  can include a follower and biasing member (not shown) configured to urge the cartridges away from the base plate  225  and into engagement with the lips  260 ,  265 . 
     In order to load cartridges  230  into the detachable magazine  200 , the base portion  245 B of a casing  235  is positioned under the lips  260 ,  265  in opposition to a biasing force exerted on the casing  230  by the follower and biasing member described above. The casing  235  can then be moved rearward and downward to the loaded position shown in  FIGS. 2B-2D , thereby moving the base portion  245 B of the casing  235  into proximity with the rear portion  220  of the detachable magazine  200 . Subsequent cartridges  230  can also be loaded into position as shown in  FIG. 2B . A cartridge in direct communication with the lips  260 ,  265  can be referred to as being in a first position while cartridges within the detachable magazine below the first position can be referred to as being in second positions. 
     As previously introduced, when cartridges  230  are loaded into the detachable magazine  200 , the neck portion  245 B, the shoulder portion  250 B, and the base portion  255 B are in proximity with the neck portion  245 A, the shoulder portion  250 A, and the base portion  255 A of the detachable magazine  200 . Such a configuration allows the detachable magazine  200  to retain the shoulder portion  250 B of the casing  235  to help reduce impact between the front portion  205  of the detachable magazine  200  and/or help ensure proper feeding of the cartridge  230 . 
     For example, while a cartridge  230  is in one of the second positions, a space between tips of projectiles  240  and the front portion  205  of the detachable magazine  200  can help ensure that relative movement between the cartridge  230  and the detachable magazine  200 , such as can occur during recoil, does not result in contact between the projectile  240  and the front portion  205 . For example, the shoulder portion  250 A of the detachable magazine  200  can interact with the shoulder portion  240 B of the casing  235 . 
     In particular, an internal width of the neck portion  245 A of the detachable magazine  200  corresponds closely to the nominal size of the neck portion  245 B of a type of cartridge  230  to be used with the detachable magazine. For example, the neck portion  245 A can have a width that is approximately 0.005 inches to about 0.04 inches or more greater than the nominal size of the neck portion  245 B of the casing  235 . Further, such a width can have a range that is approximately 0.01 inches to about 0.025 inches. Accordingly, in the case of a detachable magazine configured for use with .338 Lapua Magnum cartridges with a nominal diameter of 0.372 inches, a neck portion can have a width of between about 0.377 inches to about 0.412 inches, such as a width of between about 0.382 inches to about 0.397 inches. Such clearances can be optimized for a magazine formed from rolled and stamped steel. A relatively larger clearance, such as a clearance of greater than 0.04 inches to about 0.06 inches or more can be provided so long as the clearance retains the shoulder portion of the casing and prevents the shoulder portion from jamming into the neck portion of the magazine. Accordingly, in some examples clearance between a neck portion of the magazine adjacent the shoulder portion of the magazine can be selected according the material used to form the detachable magazine to thereby reduce or eliminate the potential for a shoulder portion of a casing to become jammed in the neck portion of a magazine. 
     Similarly, in the case of a detachable magazine configured for use with .300 Winchester Magnum cartridges with a nominal diameter of 0.339 inches, a neck portion can have a width of approximately 0.344 inches to about 0.379 inches, such as a width of between about 0.349 inches and about 0.364 inches. A detachable magazine configured for use with .308 Winchester cartridges with a nominal case neck diameter of 0.343 inches can have a width of approximately 0.348 inches to about 0.383 inches, such as a width of between about 0.353 inches and about 0.368 inches. Further, it will be appreciated that detachable cartridges can be configured for use with any type of cartridge as desired. 
     It has been found that maintaining the width of neck portions within this range can help reduce the possibility that cartridges will slip forward in response to forces, such as recoil. Preventing cartridges from slipping forward can reduce or eliminate contact between the projectile  240  and the front portion  205  of the detachable magazine  200  as well as reducing the likelihood that the shoulder portion  250 B of the casing  235  can become wedged into the shoulder portion  250 A of the detachable magazine  200  thereby reducing the likelihood of miss-feeds and thus providing shoulder retention. 
     The neck portion  245 A of the detachable magazine  200  can have the width described above for any desired length within the detachable magazine, including the entire height, a partial height, or any other combination of heights. Accordingly, the detachable magazine  200  is configured to carry several cartridges in such a manner as to reduce or eliminate contact between a cartridge&#39;s projectile and a front portion of the detachable magazine while preventing the cartridge from being wedged into some portion of the detachable magazine. While a cartridge or cartridges  230  are thus loaded in the detachable magazine  230 , the lips  260 ,  265  cooperate with the follower and biasing member to maintain a cartridge  230  in position to be fed into position in the barrel by an action. The lips  260 ,  265  can be positioned and oriented such that part of the base portion  245 B of the casing  235  extends above the rear portion  220  of the detachable magazine while a cartridge  230  is in the first position described above. 
     Placing the base portion  245 B of the casing  235  in this position allows an action to engage a cartridge  230  in the first position and cycle the cartridge forward to be fired. As shown in  FIG. 2D , the front portion  205  of the detachable magazine  200  can include a scalloped upper edge  270 , which can provide clearance between the front portion  205  and the projectile  240  as the cartridge  230  is cycled forward. 
     As the cartridge  230  is cycled forward, the biasing member moves the follower described above toward the lips  260 ,  265 . If a cartridge is in a second position, the follower moves the cartridge into the first position. A spent casing is extracted and ejected by the action as it cycles rearwardly, thereby placing the action in position to load another cartridge, thus repeating the cycle. 
     Accordingly, a plurality of cartridges can be loaded into a detachable magazine with shoulder retention features. The detachable magazine can securely retain the cartridges and help reduce or eliminate impact between a projectile and the front portion of the detachable magazine due to recoil or other forces. The size of the neck portion can be selected to help reduce or eliminate the potential for the neck portion of cartridges from becoming wedged into the corresponding neck portion of the detachable magazine. 
     In the illustrated example, one or more of the lateral portions  210 ,  215  includes a recess  270  defined therein for receiving a magazine release mechanism associated with a stock. Accordingly, the detachable magazine  200  can be released by selective engagement with the recess  270  and a corresponding tab of a magazine release mechanism. While a detachable magazine is shown, it will be appreciated that any type of magazine can be configured as described above. Such magazine types can include fixed, semi-fixed, or any other type of magazine. Further, while operation of the magazines has been described with reference to a bolt-action firearm, it will be appreciated that a magazine configured as described above can be used with any type of action. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.