Abstract:
A high capacity magazine for high powered rimfire cartridges comprises a header portion that has a form factor to be received in a rotary magazine receptacle and an arcuate cartridge bank portion that holds a column of cartridges. A pair of clamshell halves define an arcuate cartridge bank and a lower portion of the header potion. A header caps the upper ends of the clamshell halves securing the clamshell halves together. The head and clamshell halves define the cartridge pathway to the magazine exit to be fed into the rifle chamber.

Description:
BACKGROUND OF THE DISCLOSURE 
       [0001]    In shooting sports, high-performance low-cost ammunition is highly desirable. High performance can mean, for example, high accuracy at long ranges. Traditionally, center fire cartridges provide such performance, but, they are relatively expensive. Rimfire cartridges have provided inexpensive cartridges with reasonable performance. In recent years, the .17 Horady Magnum Rimfire (.17 HMR) cartridge has become very popular in applications such as varmint hunting. This cartridge produces an extremely high muzzle velocity (e.g., twice the speed of sound), much higher than conventional rimfire cartridges. This high muzzle velocity combined with the relatively low wind resistance of the .17 projectile combine to minimize bullet drop and produce a relatively flat trajectory thus offering the high performance of center fire cartridges at a rimfire price. Rifles that chamber the .17 HMR are commercially available, for example, from Savage Arms, Marlin Firearms and Sturm, Ruger &amp; Company. Such inexpensive high performance cartridges are conducive to high volume firing, especially since a semiautomatic rifle, the model A17, that accepts such cartridges is now available from Savage Arms. The A17, and other rimfire rifles, particularly semiautomatic rimfire rifles, utilize a rotary magazine that fits within a magazine receptacle in such rifles and is within the form factor of the rifles. That is, the exposed surface of the magazine follows the contours of the rifle. Low-cost high capacity magazines are known that plug into the receptacle for the rotary magazines for 22 caliber rimfire cartridges. Improvements to such high capacity magazines to accommodate the larger and higher powered .17 HMR cartridges would be well received. 
       SUMMARY 
       [0002]    A high capacity magazine for high powered rimfire cartridges comprises a header portion that has a form factor to be received in a rotary magazine receptacle and an arcuate cartridge bank portion that holds a column of cartridges. A pair of clamshell halves define an arcuate cartridge bank and a lower portion of the header potion. A header caps the upper ends of the clamshell halves securing the clamshell halves together. The head and clamshell halves define the cartridge pathway to the magazine exit to be fed into the rifle chamber. 
         [0003]    A magazine for holding and dispensing a plurality of cartridges comprises a magazine body including a port body portion and a starboard body portion. The port body portion comprises a front port wall, a rear port wall, and a port side wall extending between the front port wall and the rear port wall. The port body portion further comprises a first port rail and a second port rail that are supported by the port side wall. The starboard body portion comprises a front channel wall, a rear channel wall, and a starboard side wall extending between the front channel wall and the rear channel wall. The inside surfaces of the channel walls define a channel and the starboard side channel wall defines a slot fluidly communicating with the channel, the slot extending through the starboard side channel wall. The starboard body portion further comprises a front starboard wall and a first starboard side wall extending between the front starboard wall and the front channel wall. The front starboard wall supports a first starboard rail of the starboard body portion. The starboard body portion further comprises a rear starboard wall and a second starboard side wall extending between the rear starboard wall and the rear channel wall. The rear starboard wall supports a second starboard rail of the starboard body portion. 
         [0004]    The magazine body defines a cartridge receiving volume that is defined in a first dimension between the front and rear walls of the body portions. The cartridge receiving volume is defined in a second dimension between a guiding surface the first rail of the port body portion and a guiding surface of the first rail of the starboard body portion and between a guiding surface of the second rail of the port body portion and a guiding surface of the second rail of the starboard body portion. A follower assembly is slidingly received in the cartridge receiving volume defined by the magazine body. The follower assembly comprises a follower arm and a follower base that are both slidingly received in the cartridge receiving volume defined by the magazine body. The cartridge receiving volume extends along an undulating cartridge path that undulates in a port direction and a starboard direction and the follower arm is pivotally coupled to the follower base so that the follower arm is free to pivot about a pivot axis relative to the follower base as the follower assembly moves along the undulating cartridge path. The follower base comprises a post portion that extends starboardly into the channel defined by the channel walls of the starboard body portion. 
         [0005]    The magazine includes a user-accessible lever comprising a button portion, a retaining portion, and a shaft portion extending therebetween. The button portion of the user-accessible lever is disposed outside of the magazine body. The retaining portion of the user-accessible lever engages the base portion of the follower. The shaft portion of the user-accessible lever extends through the slot defined by the starboard side channel wall and through a groove defined by the post portion of the follower base. The follower assembly further comprises a roller disposed about an outer surface of the post and a spring disposed about an outer surface of the roller. The spring comprises a ribbon biased to form a roll when the ribbon is in an unstressed state with no external forces acting thereon. An inner surface of the ribbon defines a central opening when the ribbon is free to form the roll. A roll end of the ribbon is disposed inside the central opening and a coupled end of the ribbon is coupled to the starboard body portion proximate an upper end thereof. 
         [0006]    In operation, the ribbon rolls and unrolls during relative translational motion between the follower and the magazine body. The inner surface of the ribbon applies an upwardly directed force to the post of the follower base. The upwardly directed force applied to the roller and the post of the follower base by the inner surface of the ribbon urges the follower in an upward direction. The magazine includes a header disposed at an upward end of the port body portion and the starboard body portion. The header defines a depression. An upward portion of the port body portion and upward portion of the starboard body portion extend into the depression defined by the header. 
         [0007]    A magazine for holding and dispensing a plurality of cartridges in accordance with some embodiments comprises a header and a magazine body. The header comprises a starboard header wall disposed opposite a port header wall and a front header wall extending between a forward end of the starboard header wall and a forward end of the port header wall. The header may also include a rearward header wall extending between a rearward end of the starboard header wall and a rearward end of the port header wall. In some embodiments, the header also includes an upper header wall extending between an upper portion of the starboard header wall and an upper portion of the port header wall. The header walls define a header cavity and the upper header wall defining an exit opening communicating with the header cavity in some embodiments. In some embodiments, the magazine body defines a cartridge receiving volume communicating with the exit opening. The magazine body may include a starboard body portion and a port body portion, an upper portion of each body portion extending into the header cavity with the starboard header wall and the port header wall securing the body portions against each other. 
         [0008]    In some embodiments, a first guide is fixed to the upper header wall, the first guide extending downwardly beyond a downward facing surface of the upper header wall. In some embodiments, the first guide extends downward into a guide receiving channel defined by the body portion, the guide receiving channel being dimensioned and configured to receive the first guide. In some embodiments, the first guide has a maximum guide length extending in the portward and starboard directions and a maximum guide width extending in the forward and rearward directions. The maximum guide length is greater than the maximum guide width in some embodiments. 
         [0009]    In some embodiments, a first guide and a second guide are fixed to the upper header wall. The guides may extend downwardly beyond a downward facing surface of the upper header wall. In some embodiments, the first guide and the second guide conduct cartridges along an exit path between the cartridge receiving volume and the exit opening. In some embodiments, the exit path extends in a path direction disposed at an angle relative to a vertical reference axis, the vertical reference axis extending in upward and downward directions. 
         [0010]    Some embodiments comprise a high capacity magazine for rimfire cartridges, the magazine to be received within a rifle, the rifle configured for accepting a rotary magazine within the rifle at a rotary magazine slot, the high capacity magazine having a head portion sized to be received in the rotary magazine slot, the head portion having a cartridge exit slot, and an arcuate cartridge bank extending downwardly and forwardly from the head portion, the arcuate cartridge bank having an internal open column for receiving a stacked arrangement of rimfire cartridges. In some embodiments, the high capacity magazine comprises a pair of clam shell portions couplable together. When coupled, the clam shell portions define the arcuate cartridge bank and having a pair of upper ends that define a lower portion of the head portion. In some embodiments, the high capacity magazine comprises a header that caps the upper ends of the pair of clam shell portions thereby securing the clam shell portions together. In some embodiments, the high capacity magazine comprises a slider with a cartridge pusher positioned in the internal open column with an externally viewable capacity indicator, and spring connecting between the slider and one of the head portion and arcuate cartridge bank for causing a bias of the slider toward the head portion thereby urging a stack of cartridges in the internal cartridge column toward the cartridge exit slot. 
         [0011]    A feature and advantage of embodiments is a simple and robust assembly in which a metal header secures together two polymer clam shell portions. The metal header is highly suitable for capturing the ends of the clam shell portions and also provides a metal bearing surface that engages the rifle on insertion into the magazine slot and that provides greatly enhanced wear resistance over conventional polymer surfaces. 
         [0012]    A feature and advantage of embodiments is an externally accessible lever that allows a user to reduce or eliminate the biasing force provided by a follower spring. 
         [0013]    A feature and advantage of embodiments is a magazine body defining an undulating path to be traveled by each cartridge in a stack of cartridges held in the magazine. The undulating nature of the path traveled by each cartridge may alleviate stack up and presentation issues. 
         [0014]    A feature and advantage of embodiments is a pre-defined track configured to provide smooth translational motion of cartridges as the advance through the magazine. 
         [0015]    A feature and advantage of embodiments is a two piece follower design including a follower arm that is pivotally coupled to a follower base. This arrangement allows the upper end of the follower arm to travel independently off axis relative to the follower base, spring, and user-accessible lever. The ability of the follower arm to pivot relative to the follower base increased the ability of the follower to travel along an undulating path without excessive friction or binding. 
         [0016]    A feature and advantage of embodiments is a magazine that is compatible with magazine loader devices, such as, by way of example and not limitation, the magazine loaders shown in the following U.S. patents: U.S. Pat. No. 5,301,449, U.S. Pat. No. 4,939,862 and U.S. Pat. No. 4,739,572. These U.S. patents are incorporated by reference herein. 
         [0017]    A feature and advantage of embodiments is a header which engages the upper end of the magazine body at multiple points of contact located at varying heights. With this arrangement, the transition step between the magazine body and the header for the inner ammunition track is less likely to impede or holdup the travel of the cartridges moving upward during feeding or extraction. 
         [0018]    A feature and advantage of embodiments is a header which captures the port side portion of the body and the starboard side portion of the body through mechanically interlocking geometry. 
         [0019]    A feature and advantage of embodiments is a spring that applies a substantially constant upwardly directed feeding for to the base portion of the follower assembly. The spring comprising a ribbon biased to form a roll when the ribbon is in an unstressed state with no external forces acting thereon. An inner surface of the ribbon defining a central opening when the ribbon is free to form the roll. A post of the follower base portion extends through the central opening of the roll so that the inner surface of the ribbon applies an upwardly directed force to the outside surface of the post. In an embodiment, the ribbon is sufficiently thin that the geometry of the roll near the post remains nearly constant as the ribbon rolls and unrolls and the force applied to the outer surface of the post by the inner surface of the ribbon is nearly constant. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0020]      FIG. 1  is perspective view showing a firearm and a magazine in accordance with the detailed description. 
           [0021]      FIG. 2  is an enlarge perspective view of the magazine shown in  FIG. 1 . 
           [0022]      FIG. 3  is an exploded perspective view of the magazine shown in  FIG. 2 . 
           [0023]      FIG. 3  is a perspective view of a follower assembly. 
           [0024]      FIG. 5  is an exploded perspective view of the follower assembly shown in  FIG. 4 . 
           [0025]      FIG. 6  is an enlarged exploded perspective showing a portion of the follower assembly shown in  FIG. 5 . 
           [0026]      FIG. 7A  is a diagram illustrating an undulating cartridge path P that undulates in a port direction and a starboard direction and a follower arm that is pivotally coupled to a follower base so that the follower arm is free to pivot about a pivot axis relative to the follower base as the follower assembly moves along the undulating cartridge path P. 
           [0027]      FIG. 7B  is a side view of a follower assembly including a follower arm that is pivotally coupled to a follower base so that the follower arm is free to pivot about a pivot axis relative to the follower base. 
           [0028]      FIG. 8A  is a side view of a follower assembly including a follower arm that is pivotally coupled to a follower base so that the follower arm is free to pivot about a pivot axis relative to the follower base. 
           [0029]      FIG. 8B  is a side view of a follower assembly including a follower arm that is pivotally coupled to a follower base so that the follower arm is free to pivot about a pivot axis relative to the follower base. 
           [0030]      FIG. 9  is a diagram illustrating an undulating cartridge path P that undulates in a port direction and a starboard direction. 
           [0031]      FIG. 10A  is a side view of a cartridge magazine in accordance with the detailed description. 
           [0032]      FIG. 10B  is section view taken along section line B-B shown in  FIG. 10A . 
           [0033]      FIG. 11A  is a top section view of a cartridge magazine in accordance with the detailed description. 
           [0034]      FIG. 11B  is a perspective section view of a cartridge magazine in accordance with the detailed description. 
           [0035]      FIG. 12  is a side view showing a port body portion of a cartridge magazine in accordance with the detailed description. 
           [0036]      FIG. 13  is a side view showing a starboard body portion of a cartridge magazine in accordance with the detailed description. 
           [0037]      FIGS. 14A-14F  are a plurality of plan and elevation views showing a base portion of a follower assembly.  FIGS. 14A-14F  are located and oriented in a manner consistent with engineering drawings including multiple orthographic projection views. 
           [0038]      FIGS. 15A-15F  are a plurality of plan and elevation views showing a follower arm.  FIGS. 15A-15F  are located and oriented in a manner consistent with engineering drawings including multiple orthographic projection views. 
           [0039]      FIG. 16  is a perspective view showing a header of a cartridge magazine in accordance with the detailed description. 
           [0040]      FIG. 17  is a perspective view showing a port body portion and a starboard body portion of a cartridge magazine in accordance with the detailed description. 
           [0041]      FIG. 18A  is a bottom view of a header in accordance with the detailed description. 
           [0042]      FIG. 18B  is a section view a header that has been sectioned along section line B-B shown in  FIG. 18A . 
           [0043]      FIG. 19  is a perspective view of an assembly including the starboard body portion shown in  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    Referring to  FIG. 1 , a rimfire rifle  20  has a magazine slot  24  for receiving a rotary magazine  28 . The rotary magazine being substantially contained within the rifle when inserted with only a lower side  32  and surface  36  of the rotary magazine exposed. The rotary magazine having a latch  34  for retention of the magazine in the magazine slot  24 . The lower side and surface of the rotary magazine conforming shapewise to the lower surface  40  of the rifle  20  when inserted. A high capacity magazine  50  has an insertable head portion  56  and an arcuate cartridge bank portion  60 . The head portion conforming to the shape of the rotary magazine  28 . A latch  64  retains the high capacity magazine in the magazine slot. 
         [0045]    Referring to  FIGS. 2-19 , a magazine  50  for holding and dispensing a plurality of cartridges comprises a magazine body  102  including a port body portion  104  and a starboard body portion  106 . The port body portion  104  comprises a front port wall  160 , a rear port wall  162 , and a port side wall  164  extending between the front port wall  160  and the rear port wall  162 . The port body portion  104  further comprises a first port rail  166  and a second port rail  168  that are supported by the port side wall  164 . The starboard body portion  106  comprises a front channel wall  180 , a rear channel wall  182 , and a first starboard side wall  174  extending between the front channel wall  180  and the rear channel wall  182 . The inside surfaces of the channel walls define a channel  190  and the starboard side channel wall  184  defines a slot  192  fluidly communicating with the channel  190 . The slot  192  extends through the starboard side channel wall  184 . The starboard body portion  106  further comprises a front starboard wall  170  and a first starboard side wall  174  that extends between the front starboard wall  170  and the front channel wall  180 . The front starboard wall  170  supports a first starboard rail  176  of the starboard body portion  106 . The starboard body portion  106  further comprises a rear starboard wall  172  and a second starboard side wall  175  extending between the rear starboard wall  172  and the rear channel wall  182 . The rear starboard wall  172  supports a second starboard rail  178  of the starboard body portion  106 . 
         [0046]    The magazine body  102  defines a cartridge receiving volume V that is defined in a first dimension between the front and rear walls of the body portions. The cartridge receiving volume V is defined in a second dimension between a guiding surface the first rail  166  of the port body portion  104  and a guiding surface of the first rail  176  of the starboard body portion  106  and between a guiding surface of the second rail  168  of the port body portion  104  and a guiding surface of the second rail  178  of the starboard body portion  106 . A follower assembly  120  is slidingly received in the cartridge receiving volume V defined by the magazine body  102 . The follower assembly  120  comprises a follower arm  124  and a follower base  122  that are both slidingly received in the cartridge receiving volume V defined by the magazine body  102 . The cartridge receiving volume V extends along an undulating cartridge path P that undulates in a port direction and a starboard direction and the follower arm  124  is pivotally coupled to the follower base  122  so that the follower arm  124  is free to pivot about a pivot axis relative to the follower base  122  as the follower assembly  120  moves along the undulating cartridge path P. The follower base  122  comprises a post portion  126  that extends starboardly into the channel  190  defined by the channel walls of the starboard body portion  106 . 
         [0047]    The magazine  100  includes a user accessible lever  152  comprising a button portion  154 , a retaining portion  158 , and a shaft portion  156  extending therebetween. The button portion  154  of the user accessible lever  152  is disposed outside of the cartridge receiving volume V. The retaining portion  158  of the user accessible lever  152  engages the base portion  122  of the follower assembly  120 . The shaft portion  156  of the user accessible lever  152  extends through the slot  192  defined by the starboard side channel wall  184  and through a groove  136  defined by the post portion  126  of the follower base  122 . The follower assembly  120  further comprises a roller  130  disposed about an outer surface  128 P of the post and a spring  140  disposed about an outer surface  128 R of the roller  130 . The spring  140  comprises a ribbon  142  biased to form a roll  144  when the ribbon  142  is in an unstressed state with no external forces acting thereon. An inner surface  132 S of the ribbon  142  defines a central opening  146  when the ribbon  142  is free to form the roll  144 . A roll end of the ribbon  142  is disposed inside the central opening  146  and a coupled end of the ribbon  142  is coupled to the starboard body portion  106  proximate an upper end thereof. In an embodiment, the coupled end of the ribbon  142  is coupled using a pin  148  that extends through a hole  150 S defined by the ribbon  142 . 
         [0048]    In operation, the ribbon  142  rolls and unrolls during relative translational motion between the follower assembly  120  and the magazine body  102 . The inner surface  132 S of the ribbon  142  applies an upwardly directed force to the roller  130  and the post  126  of the follower base  122 . The upwardly directed force applied to the post  126  of the follower base  122  by the inner surface  132 S of the ribbon  142  urges the follower assembly  120  in an upward direction U. The magazine  100  includes a header  108  disposed at an upward ends of the port body portion  104  and the starboard body portion  106 . The header  108  defines a cavity  200 . An upward portion of the port body portion  104  and an upward portion of the starboard body portion  106  extend into the cavity  200  defined by the header  108 . 
         [0049]    Referring to  FIGS. 7-9 , a feature and advantage of embodiments is a magazine body defining an undulating path P to be traveled by each cartridge in a stack of cartridges held in the magazine. The undulating nature of the path P traveled by each cartridge may alleviate stack up and presentation issues. 
         [0050]    Referring to  FIGS. 7-9 , a feature and advantage of embodiments is a two piece follower design including a follower arm  124  that is pivotally coupled to a follower base portion  122 . This arrangement allows the upper end of the follower arm  124  to travel independently off axis relative to the follower base portion  122  as the follower travels through an undulating path P to be traveled by each cartridge in a stack of cartridges held in the magazine. The ability of the follower arm  124  to pivot relative to the follower base portion  122  increased the ability of the follower to travel along an undulating path P without excessive friction or binding. 
         [0051]    Referring to  FIGS. 3-6 , a feature and advantage of embodiments is a spring  140  that applies a substantially constant upwardly directed feeding for to the base portion of the follower assembly. The spring  140  comprising a ribbon  142  biased to form a roll  144  when the ribbon  142  is in an unstressed state with no external forces acting thereon. An inner surface of the ribbon  142  defining a central opening when the ribbon  142  is free to form the roll  144 . A post portion  124  of the follower base portion extends through the central opening of the roll  144  so that the inner surface of the ribbon  142  applies an upwardly directed force to a roller  130  and the outside surface of the post portion  124 . In an embodiment, the ribbon  142  is sufficiently thin that the geometry of the roll  144  near the post portion  124  remains nearly constant as the ribbon  142  roll  144   s  and unroll  144   s  and the force applied to the outer surface of the post portion  124  by the inner surface of the ribbon  142  is nearly constant. 
         [0052]    Referring to  FIGS. 16-18 , in an embodiment, the header  108  forms a mechanically interlocking engagement with the port body portion  104  and the starboard body portion  106  so as to hold the port body portion  104  and the starboard body portion  106  against one another. Header  108  defines a cavity  200  that is dimensioned and configure to receive an upper protrusion  202 P of port body portion  104  and an upper protrusion  202 S of starboard body portion  106 . Header  108  comprises a starboard header wall  204 A, a rearward header wall  204 B, a port header wall  204 C and a forward header wall  204 D. Cavity  200  is partially defined by the starboard header wall  204 A, the rearward header wall  204 B, the port header wall  204 C and the forward header wall  204 D. 
         [0053]    The starboard body portion  106  comprises a tab  206  and header  108  comprises a corresponding tab receiving feature  208 . The tab receiving feature  208  of header  108  is dimensioned and configured to receive the tab  206  of the starboard body portion  106 . The header  108  comprises a second guide  222  and starboard body portion  106  comprises a corresponding guide receiving groove  222 . The guide receiving groove  222  of the starboard body portion  106  is dimensioned and configured to receive the second guide  222  of the header  108 . The header  108  comprises a first guide  224  and the port body portion  104  comprises a corresponding guide receiving channel  226 . The guide receiving channel  226  of the port body portion  104  is dimensioned and configured to receive the first guide  224  of the header  108 . The header  108  comprises a first rib  228 A and a second rib  228 B. The starboard body portion  106  includes a rib receiving feature  230  that is dimensioned and configured to receive the first rib  228 A and the second rib  228 A of the header  108 . The header  108  comprises a ledge  232  and the port body portion  104  comprises a corresponding plateau  234 . The plateau  234  of the port body portion  104  is dimensioned and configured to support the ledge  232  of the header  108 . The header  108  comprises a peak  236  and the port body portion  104  comprises a corresponding valley  238 . The valley  238  of the port body portion  104  is dimensioned and configured to receive the peak  236  of the header  108 . The header  108  comprises a bar  240  and starboard body portion  106  comprises a corresponding bar receiving feature  242 . The bar receiving feature  242  of the starboard body portion  106  is dimensioned and configured to receive the bar  240  of the header  108 . 
         [0054]    In some embodiments, a first guide  224  is fixed to the upper header wall, the first guide  224  extending downwardly beyond a downward facing surface of the upper header wall. In some embodiments, the first guide  224  extends downward into a guide receiving channel defined by the body portion, the guide receiving channel being dimensioned and configured to receive the first guide  224 . In some embodiments, the first guide  224  has a maximum guide length extending in the portward and starboard directions and a maximum guide width extending in the forward and rearward directions. The maximum guide length is greater than the maximum guide width in some embodiments. 
         [0055]    In some embodiments, a first guide  224  and a second guide  220  are fixed to the upper header wall. The guides may extend downwardly beyond a downward facing surface of the upper header wall. In some embodiments, the first guide  224  and the second guide  220  conduct cartridges along an exit path between the cartridge receiving volume and the exit opening. In some embodiments, the exit path extends in a path direction disposed at an angle relative to a vertical reference axis, the vertical reference axis extending in upward and downward directions. 
         [0056]    A magazine for holding and dispensing a plurality of cartridges in accordance with some embodiments comprises a header  108  and a magazine body. The header comprises a starboard header wall  204 A disposed opposite a port header wall  204 C and a front header wall  204 D extending between a forward end of the starboard header wall  204 A and a forward end of the port header wall  204 C. The header may also include a rearward header wall  204 B extending between a rearward end of the starboard header wall  204 A and a rearward end of the port header wall  204 C. In some embodiments, the header also includes an upper header wall extending between an upper portion of the starboard header wall  204 A and an upper portion of the port header wall  204 C. The header walls define a header cavity and the upper header wall defining an exit opening communicating with the header cavity in some embodiments. In some embodiments, the magazine body defines a cartridge receiving volume communicating with the exit opening. The magazine body may include a starboard body portion  106  and a port body portion  104 , an upper portion of each body portion extending into the header cavity with the starboard header wall  204 A and the port header wall  204 C securing the body portions against each other. 
         [0057]    Referring to  FIGS. 1-19 , a high capacity magazine  100  for rimfire cartridges in accordance with some embodiments comprises a pair of clam shell portions couplable together. When coupled, the clam shell portions  104 ,  106  define and arcuate cartridge bank volume V and have a pair of upper ends that define a lower portion of the head portion. In some embodiments, the high capacity magazine  100  comprises a header  108  that caps the upper ends of the pair of clam shell portions  104 ,  106  thereby securing the clam shell portions  104 ,  106  together. In some embodiments, the high capacity magazine  100  comprises a slider assembly  120  with a cartridge pusher  124  positioned in the cartridge bank volume V and with an externally viewable capacity indicator  154 , and a spring  140  connecting between a portion  122  of the slider assembly  120  and one of the head portion and the arcuate cartridge bank volume V for causing a bias of the slider assembly  120  toward the head portion thereby urging a stack of cartridges in the cartridge bank volume V toward a cartridge exit opening defined by the header  108 . 
         [0058]      FIG. 1  is perspective view showing a firearm  20  and a magazine  100 . In  FIG. 1 , an upward direction U and a downward direction D are illustrated using arrows labeled “U” and “D.” A forward direction F and a rearward direction R are illustrated using arrows labeled “F” and “R,” respectively, in  FIG. 1 . A starboard direction S and a port direction P are illustrated using arrows labeled “S” and “P,” respectively, in  FIG. 1 . In the embodiment of  FIG. 1 , these directions may be conceptualized from the point of view of a user who is holding the firearm F. 
         [0059]    Various direction-indicating terms are used herein as a convenient way to discuss the objects shown in the figures. It will be appreciated that many direction indicating terms are related to the instant orientation of the object being described. It will also be appreciated that the objects described herein may assume various orientations without deviating from the spirit and scope of this detailed description. Accordingly, direction-indicating terms such as “upwardly,” “downwardly,” “forwardly,” “backwardly,” “portly,” and “starboardly,” should not be interpreted to limit the scope of the invention recited in the attached claims. 
         [0060]    The following United States patents are hereby incorporated by reference herein: U.S. Pat. No. 2,765,558, U.S. Pat. No. 2,777,235, U.S. Pat. No. 3,087,270, U.S. Pat. No. 3,577,860, U.S. Pat. No. 4,127,954, U.S. Pat. No. 4,566,212, U.S. Pat. No. 4,580,364, U.S. Pat. No. 4,672,760, U.S. Pat. No. 4,765,081, U.S. Pat. No. 4,776,122, U.S. Pat. No. 4,790,094, U.S. Pat. No. 4,888,899, U.S. Pat. No. 5,502,913, U.S. Pat. No. 7,011,028, U.S. Pat. No. 8,407,922, U.S. Pat. No. 8,991,086, U.S. Pat. No. 5,301,449, U.S. Pat. No. 4,939,862, U.S. Pat. No. 4,739,572, and U.S. Pat. No. 3,239,959. 
         [0061]    The above references to U.S. patents in all sections of this application are herein incorporated by references in their entirety for all purposes. Components illustrated in such patents may be utilized with embodiments herein. Incorporation by reference is discussed, for example, in MPEP section 2163.07(B). 
         [0062]    United States patents issuing from the following published United States patent applications are hereby incorporated by reference herein: US20150330727, 20150330734 and 20150330731. The following published United States patent applications are also hereby incorporated by reference herein: US20150330727, 20150330734 and 20150330731. 
         [0063]    All of the features disclosed in this specification (including the references incorporated by reference, including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0064]    Each feature disclosed in this specification (including references incorporated by reference, any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0065]    The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any incorporated by reference references, any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed The above references in all sections of this application are herein incorporated by references in their entirety for all purposes. 
         [0066]    Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose could be substituted for the specific examples shown. This application is intended to cover adaptations or variations of the present subject matter. Therefore, it is intended that the invention be defined by the attached claims and their legal equivalents, as well as the following illustrative aspects. The above described aspects embodiments of the invention are merely descriptive of its principles and are not to be considered limiting. Further modifications of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention.