Abstract:
A magazine for storing and feeding ammunition cartridges to a small arms weapon which comprises a casing, a floor plate, a follower, and a magazine spring inside the casing. The magazine spring may comprise a first end connected to the follower, a second end connected to the floor plate, and a plurality of coils. Each of the plurality of coils may include a first segment having a first radius, a second segment having a first length adjoining the first segment, a third segment having a second radius adjoining the second segment, the second radius being greater than the first radius, and a fourth segment having a second length adjoining the third segment, the second length being approximately equal to the first length.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application No. 29/472,057 filed Nov. 7, 2013. This application claims the benefit of provisional Application No. 61/912,521 filed Dec. 5, 2013. The disclosure of each of these applications is incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to a method for storing and feeding ammunition cartridges to a small arms weapon. More particularly, this invention relates to an ammunition magazine for a small arms weapon. This invention also relates to a resilient biasing member for moving ammunition cartridges through a magazine. 
     BACKGROUND 
     Reliable delivery of ammunition from an external supply into a firearm chamber is an important aspect of effective firearm operations. The structure and capacity of the external supply of ammunition may affect the consistency of ammunition delivery. Additionally, the ability of the external supply to be detached from the firearm, reloaded with ammunition, and then reused with the firearm may enhance the effectiveness of firearm operations. Although ammunition magazines (e.g., STANAG or STANAG-compatible box magazines) are known, some ammunition magazines may lack durability or tend to malfunction. Accordingly, a need exists for new ammunition storage and feeding devices. 
     SUMMARY 
     Hence, the present invention is directed to an ammunition magazine for storing and feeding ammunition cartridges to a firearm. The present invention is also directed to a magazine spring. 
     One aspect of the present invention relates to a magazine for storing and feeding ammunition cartridges to a small arms weapon. The magazine may include a casing which comprises an upper end and a lower end, a floor plate situated near the lower end, a follower adjacent the floor plate, and a magazine spring inside the casing. The magazine spring may comprise a first end connected to the follower, a second end connected to the floor plate, and a plurality of coils. Each of the plurality of coils may include a first segment having a first radius, a second segment having a first length adjoining the first segment, a third segment having a second radius adjoining the second segment, the second radius being greater than the first radius, and a fourth segment having a second length adjoining the third segment, the second length being approximately equal to the first length. The second radius divided by the first radius may define a coil ratio. Preferably, the coil ratio may be between approximately 1.1 and approximately 1.5. 
     In another aspect, the magazine spring may be preloaded for a force of approximately 15 N at a reference length of approximately 180 mm. The magazine spring further may have a solid height that is less than or equal to approximately 25 mm. Moreover, the second radius may be approximately 8.1 mm and the first radius may be approximately 6.5 mm. The magazine spring may be formed from a round wire. The round wire may have an outer diameter of approximately 1.5 mm and may be music wire per ASTM A228. 
     In another aspect, the magazine spring may be preloaded for a force of approximately 15 N at a reference length of approximately 75 mm. The magazine spring may have a solid height less than or equal to approximately 20 mm. The second radius may be approximately 8.1 mm and the first radius may be approximately 6.1 mm. The magazine spring may be formed from a round wire. The round wire may have an outer diameter of approximately 1.5 mm and may be music wire per ASTM A228 
     In another aspect, the magazine casing may be configured and dimensioned to store a plurality of ammunition cartridges for a small arms weapon. For example, the casing may be configured and dimensioned to store 30 or fewer ammunition cartridges. In another example, the casing may be configured and dimensioned to store 10 or fewer ammunition cartridges. The casing may be configured and dimensioned to store 5.56×45 mm NATO cartridges or .223 Remington cartridges. 
     Another aspect of the present invention relates to a magazine spring for an ammunition magazine for a small arms weapon. The magazine spring may include a wire which comprises a plurality of coils. Each of the plurality of coils may include a first segment having a first radius, a second segment having a first length adjoining the first segment, a third segment having a second radius adjoining the second segment, the second radius being greater than the first radius, and a fourth segment having a second length adjoining the third segment, the second length being approximately equal to the first length. The second radius further may be divided by the first radius to define a coil ratio, and the coil ratio may be at least about 1.05. 
     In another aspect, the coil ratio may be less than about 3. Preferably, the coil ratio may range from approximately 1.10 to approximately 1.50. More preferably, the coil ratio may range from approximately 1.20 to approximately 1.35. In an exemplary embodiment of the invention, the coil ratio is approximately 1.25. In another exemplary embodiment, the coil ratio is approximately 1.32. 
     In another aspect, the wire may have a preloaded force of approximately 15 N for a reference length that ranges from approximately 75 mm to approximately 180 mm. 
     In another aspect, the second radius may be between approximately 7.8 mm and 8.4 mm. 
     In a preferred embodiment, the first radius may be between approximately 5.8 mm and approximately 6.4 mm. 
     In another preferred embodiment, the first radius may be between approximately 6.2 mm and approximately 6.4 mm. 
     In another aspect, each of the plurality of coils may have a maximum outer dimension between approximately 49.2 mm and approximately 49.8 mm. 
     In another aspect, the wire may be a round wire, a stranded wire, or a shaped wire. The shaped wire may be is selected from one of the group consisting of square, rectangular, keystone, oval, elliptical, half round, or D-shaped. 
     In another aspect, the wire may be carbon steel. For example, the wire may be music wire. 
     In another aspect, the wire may be alloy steel. For example, the wire may be chrome silicon. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals (or designations) are used to indicate like parts in the various views: 
         FIG. 1  is a perspective view of an exemplary embodiment of an ammunition magazine in accordance with the present invention; 
         FIG. 2  is top view of the magazine of  FIG. 1 ; 
         FIG. 3  is a perspective view of the magazine of  FIG. 1  loaded in an AR-15 type firearm; 
         FIG. 4  is another perspective view of the magazine of  FIG. 1 , the magazine being loaded with ammunition cartridges; 
         FIG. 5  is a partial perspective view of the casing of the magazine of  FIG. 1 ; 
         FIG. 6  is an exploded view of the magazine of  FIG. 1 , along with a cartridge that may be stored in the magazine; 
         FIG. 7  is a cross-sectional view of the magazine of  FIG. 1 , along line  7 - 7 , where the magazine is empty and the follower and spring are in an extended configuration; 
         FIG. 8  is a partial cross-sectional view of the magazine of  FIG. 1 , along line  7 - 7 , where the magazine is partially loaded with ammunition cartridges and the follower and spring are in a depressed configuration; 
         FIG. 9  is a partial cross-sectional view of the magazine of  FIG. 1 , along line  7 - 7 , where the magazine is fully loaded with ammunition cartridges and the follower and spring are in a nearly fully depressed configuration; 
         FIG. 9   a  is a partial cross-sectional view of another embodiment of the magazine of  FIG. 1 , along line  7 - 7 , where the magazine is fully loaded with ammunition cartridges and the follower and spring are in a fully depressed configuration; 
         FIG. 9   b  is a partial cross-sectional view of yet another embodiment of the magazine of  FIG. 1 , along line  7 - 7 , where the magazine is fully loaded with ammunition cartridges and the follower and spring are in a fully depressed configuration; 
         FIG. 10  is a partial cross-sectional view of the magazine of  FIG. 8 , along line  10 - 10 ; 
         FIG. 11  is a perspective view of the follower of  FIG. 1 ; 
         FIG. 12  is a cross-sectional view of the magazine of  FIG. 7 , along line  12 - 12 ; 
         FIG. 13  is a cross-sectional view of the magazine of  FIG. 7 , along line  13 - 13 ; 
         FIG. 14  is a bottom, partial perspective view of the follower and spring of  FIG. 6 ; 
         FIG. 15  is a perspective view of the floor plate of  FIG. 6 ; 
         FIG. 16  is a cross-sectional view of the magazine of  FIG. 7 , along line  16 - 16 ; 
         FIG. 17  is a partially exploded view of the bottom end of the magazine of  FIG. 1 ; 
         FIG. 18  is a perspective view of the base of  FIG. 6 ; 
         FIG. 19  is a partial cross-sectional perspective view of the magazine casing of  FIG. 8 ; 
         FIG. 20  is another partial cross-sectional perspective view of the magazine casing of  FIG. 8 ; 
         FIG. 21  is a cross-sectional view of the magazine casing of  FIG. 19 , along line  21 - 21 ; 
         FIG. 22A  is a side view of an exemplary design for the magazine spring of  FIG. 1 ; 
         FIG. 22B  is a front view of the magazine spring of  FIG. 22A ; 
         FIG. 22C  is a perspective view of the magazine spring of  FIG. 22A ; 
         FIG. 22D  is a top view of the magazine spring of  FIG. 22A ; 
         FIG. 22E  is a cross-sectional view of the spring of  FIG. 22A , along line  22 E- 22 E; 
         FIG. 22F  is a cross-sectional view of the spring of  FIG. 22A , along line  22 F- 22 F; 
         FIG. 23  is a schematic depiction of the effect of the ammunition guide surfaces and multi-faceted block on the position of six ammunition cartridges disposed in the magazine of  FIG. 1 ; 
         FIG. 24  is a cross-sectional view of the  FIG. 23 , along line  24 - 24 ; 
         FIG. 25  is a cross-sectional view of the  FIG. 23 , along line  25 - 25 ; 
         FIG. 26  is a cross-sectional view of the  FIG. 23 , along line  26 - 26 ; 
         FIG. 27  is a cross-sectional view of the  FIG. 23 , along line  27 - 27 ; 
         FIG. 28  is a cross-sectional view of the  FIG. 23 , along line  28 - 28 ; 
         FIG. 29  is a schematic depiction of the effect of the ammunition guide surfaces and multifaceted block on the position of an ammunition cartridge as a bolt carrier of an AR-15 type rifle engages an ammunition cartridge stored in the magazine of  FIG. 1 ; 
         FIG. 30  is a schematic depiction of the effect of the ammunition guide surfaces and multifaceted block on the position of the ammunition cartridges as a bolt carrier of an AR-15 type rifle feeds the engaged ammunition cartridge into the barrel extension of the rifle; 
         FIG. 31  is a schematic depiction of the effect of the ammunition guide surfaces and multifaceted block on the position of the ammunition cartridges as a bolt carrier of an AR-15 type rifle feeds the engaged ammunition cartridge into the chamber of the rifle; 
         FIG. 32  is a schematic depiction of the effect of the ammunition guide surfaces and multifaceted block on the position of the ammunition cartridges as a bolt carrier of an AR-15 type rifle locks the engaged ammunition cartridge into the chamber of the rifle; 
         FIG. 33  is a schematic depiction of the effect of the ammunition guide surfaces and multifaceted block on the position of the ammunition cartridges as a bolt carrier of an AR-15 type rifle recoils after firing and cocking the trigger; 
         FIG. 34  is a schematic depiction of the interaction between the magazine of  FIG. 1  and the AR-15 type rifle, as the tip of the resilient tab on the magazine follower pushes the bolt catch upward to stop forward travel of the bolt carrier; 
         FIG. 35  is a schematic depiction of the right side view of the magazine of  FIG. 1  loaded with 30 ammunition cartridges, as indicated by a marking on the port side wing which is visible through a window in the magazine casing; 
         FIG. 36A  shows a spring wire with a round (or circular) cross section; 
         FIG. 36B  shows a shaped spring wire with an oval cross section; 
         FIG. 36C  shows a shaped spring wire with a square cross section; 
         FIG. 36D  shows a shaped spring wire with a rectangle cross section; 
         FIG. 36E  shows a shaped spring wire with a trapezoid cross section; 
         FIG. 36F  shows a shaped spring wire with a sharp triangle cross section; 
         FIG. 36G  shows a shaped spring wire with a wedge cross section; 
         FIG. 36H  shows a shaped spring wire with an equilateral triangle cross section; 
         FIG. 36I  shows a shaped spring wire with a pie cross section; 
         FIG. 36J  shows a shaped spring wire with a half round (or D) cross section; 
         FIG. 36K  shows a stranded spring wire in cross section, the stranded spring wire being formed from three strands; and 
         FIG. 36L  shows a stranded spring wire in cross section, the stranded spring wire being formed from seven strands. 
     
    
    
     DESCRIPTION 
       FIGS. 1 and 2  show an exemplary embodiment of an ammunition magazine  10  of the present invention. As shown in  FIG. 6 , the magazine may include a housing  12 , a follower  14 , a spring  16 , a floor plate  18  and a base  20 . Referring to  FIG. 3 , the magazine  10  may be configured and dimensioned for use with an AR-15 rifle (or M-4 carbine)  22 . Referring to  FIG. 4 , the magazine  10  may be used to store and feed up to thirty ammunition cartridges  24 . Although the exemplary embodiment of the magazine is configured and dimensioned to store and feed NATO 5.56 mm cartridges or .223 Remington cartridges, other types of suitable ammunition cartridges may be used. 
     As shown in  FIG. 1 , the magazine may include an upper portion  26  which interfaces with the rifle and a lower portion  28  which is primarily handled by the user. The upper portion of the magazine may include a pair of magazine feed lips  30 ,  32 . The magazine lips may be disposed in a contra-lateral configuration. The magazine lips may be configured and dimensioned to interface with a portion of a rifle bolt. Additionally, the upper portion may include a projection  34  that is configured and dimensioned to interlock with a magazine catch on the rifle. The magazine catch may interlock with the projection to selectively secure the magazine within the rifle. 
     The lower portion  28  of the magazine may include a fore grip  36  and a rear grip  38 . The fore grip and/or the rear grip may include a region of raised features  40 . The raised features may include a plurality of geometric shapes. For example, the fore grip may include a plurality of generally rectangular shaped projections  42  and the rear grip may include a plurality of generally triangular shaped projections  44 . The projections may be arranged in one or more patterns to improve the ability of a user to hold and handle the magazine. Additionally, the lower portion of the magazine may include a window  46 . The window may be disposed between the fore grip and the rear grip. The window may provide a user with a view of the magazine interior. For example, the window may provide a view of cartridges that are stored in the magazine. 
     The magazine may include indicia  48 . The indicia may be associated with the window and may indicate the number of ammunition cartridges which are stored in the magazine. For example, the indicia may include tick marks and numbers. For instance, tick marks may be spaced on the magazine to designate storage intervals of five ammunition cartridges. Numerals may be placed by some or all of the tick marks to indicate the number of ammunition cartridges in the magazine. In  FIG. 1 , numerals are shown next to tick marks designating the 10, 20, and 30 ammunition cartridge storage interval marks. 
     As shown in  FIGS. 1 and 6 , the magazine housing  12  may include a front sidewall  50 , a rear side wall  52 , a port side wall  54  and a starboard sidewall  56 . In the exemplary embodiment, the front side wall may conform to a first imaginary curve having a radius of approximately 750 mm, and the rear side wall may conform to a second imaginary curve having a radius of approximately 810 mm. The first center point and the second center point may define a vertical axis. The first center point may be situated above the second center point. For example, the center of the first imaginary curve may be disposed above the center of the second imaginary curve such that the internal distance between the front side wall and the rear side wall at the top of the magazine may be approximately 60.4 mm and the internal distance between the front side wall  50  and the rear sidewall  52  at the bottom of the casing may be approximately 61.3 mm. Accordingly, the distance separating the front side wall and the rear sidewall at the top of the housing is approximately 1 mm less than the distance separating the front sidewall and the rear sidewall at the bottom of the housing. 
     Referring to  FIG. 5 , the housing  12  may include a front sill  62 , a rear sill  64 , a starboard side magazine feed lip  30 , a port side magazine feed lip  32 , and internal guide surfaces  66 ,  68  for the follower and ammunition cartridges. 
     As shown in  FIGS. 19 and 21 , the starboard side wall  30  may include guide surfaces  66 ,  68  for the follower and ammunition cartridges. The follower guide surfaces  66  may include a generally planar surface  70 , a concave surface  72  abutting the generally planar surface, and a convex surface  74  abutting the concave surface. These surfaces may form a bumper track  76 , which is configured and dimensioned to receive a portion of the follower. Accordingly, the starboard sidewall may include a bumper track  76  having a cross-sectional profile that includes a generally planar segment, a concave segment and a convex segment. 
     The ammunition cartridge guide surfaces  68  may include a projectile guide surface  78 , a cartridge neck guide surface  80 , and a cartridge shoulder guide surface  82 . These surfaces  78 ,  80 ,  82  may form an ammunition cartridge track  84 , which is configured and dimensioned to support a particular type of ammunition cartridge, such as a 5.56×45 mm NATO round. Accordingly, the starboard sidewall may include an ammunition cartridge track having a cross-sectional profile which, in part, resembles the contour of an ammunition cartridge. 
     The guide surfaces further may include a multi-faceted block  86 , which projects from the starboard sidewall  56  near the top of the housing. The multi-faceted block  86  may intersect the follower and ammunition cartridge guide surfaces and may include: a tapered, concave upper surface  88 ; an angled and tapered side surface  90 ; an angled sub-side surface  92 ; and an angled and tapered rear surface  94 . The multi-faceted block further may include a lower surface  96 . 
     The tapered concave upper surface  88  may be configured and dimensioned to form a ramp for directing a forward moving ammunition cartridge upward and over the front sill  62  of the housing. The angled and tapered side surface  90  may be configured and dimensioned to push the projectile of an ammunition cartridge toward the center of the housing as the cartridge moves up the face of the angled and tapered side surface  90 . 
     The angled sub-surface  92  may form a ramp which connects the angled and tapered side surface  90  and the cartridge neck guide surface  80 . The angled sub-side surface  92  may be configured and dimensioned to push the cartridge neck of an ammunition cartridge toward the center of the housing as the cartridge moves up the face of the angled sub-side surface. 
     The angled and tapered rear surface  94  may form a ramp which connects the tapered concave upper surface  88  and the ammunition cartridge shoulder guide surface  82 . The angled and tapered rear surface  94  may be configured and dimensioned to push the shoulder of an ammunition cartridge toward the rear of the housing as the cartridge moves up the face of the angled and tapered rear surface. 
     The lower surface  96  may extend from the angled and tapered side surface  90  to the bumper track  76  such that the lower surface forms an end wall for the track. The end wall may be perpendicular to the follower guide surfaces  70 ,  72 ,  74  which may form the track. 
     The starboard side magazine feed lip  30  may include internal guide surfaces  68  for stabilizing or directing movement of the ammunition cartridge body. For example, a series of curved surfaces may connect the starboard side wall to the interior side walls of the magazine feed lip. As shown in  FIGS. 19 and 21 , a rear guide surface  98 , an intermediate guide surface  100 , and a front guide surface  102  may be configured and dimensioned to direct the ammunition cartridge body upward and inward as the ammunition cartridge moves forward against the interior guide surfaces. 
     The features described above in connection with the starboard side wall  56  may be found on the port side wall  54 , as well. In general, the internal configuration of the port sidewall may be a mirror image of the starboard side wall. The starboard sidewall features described in  FIGS. 7-9  and  19 - 21 , therefore, may have complimentary counterpart features on the port sidewall. Hence, the internal guide structures within the housing may be symmetrical about a central plane  104  that bisects the front sidewall and the rear sidewall of the housing, as shown in  FIG. 20 . These structures, which are identified with common reference element numbers, may include the follower guide surfaces  76 , the ammunition cartridge guide surfaces  84 , the multi-faceted block surfaces  90 ,  92 ,  64 ,  96  and the feed lip guide surfaces  98 ,  100 ,  102 . 
     Referring to  FIGS. 7 and 17 , the bottom of the housing  12  may include a flange  106 . The flange may extend around the circumference of the housing. The housing may further include a groove  108  above the flange. The groove  108  may extend around three sides of the housing and may widen toward the ends. 
     Referring to  FIG. 11 , the follower  14  may include a front end  110 , a rear end  112 , an upper surface  114 , a lower surface  116 , and four stabilizing structures. The four stabilizing structures may include a front bumper  118 , a rear bumper  120 , a port side wing  122  and a starboard side wing  124 . 
     The upper surface  114  of the follower  14  includes a base portion  126 , an intermediate portion  128 , and a tapered front portion  130 . The base portion  126  includes a generally smooth and flat area on the port side and a raised cartridge spacer  132  on the starboard side. The cartridge spacer  132  includes a generally flat rear portion  134 , a concave shaped middle portion (or crown)  136 , and a sloped front portion  138 . The cartridge spacer may include a starboard escarpment  140  and a port escarpment  142 . The intermediate portion  128  abuts the base portion  126 . The intermediate portion  128  may be generally flat and smooth. The intermediate portion may connect the base portion  126  with the front tapered portion  130 . The front tapered portion  130  may narrow and slope downward to the front bumper  118 . 
     The follower may include an upper surface  114 , a lower surface  116 , and a side surface  144  extending between the upper surface and a lower surface. The follower may include a front bumper  118  that is disposed below the front tapered portion  130  of the upper surface. Referring to  FIG. 14 , the follower  14  may include a port side bumper  146  and a starboard side bumper  148 . The port side bumper  146  may extend laterally and curve backward from the port side of the front bumper  118 ; the starboard side bumper  148  may extend laterally and curve backward from the starboard side of the front bumper  118 . The interior surface of the front bumper, port side bumper, and starboard side bumper may form a smooth curved surface  150 . The curved surface may form a front shroud for the magazine spring. 
     The rear bumper  120  may include a stem  152  which extends downward from the rear end of the upper surface of the follower. The stem may include a resilient tab  154 . The resilient tab  154  may be integrally connected to the base of the stem  152 . The resilient tab may be configured and dimensioned to slide in a channel  156  on the rear side of the housing. The resilient tab may be flexible, and the gap between the resilient tab and the stem may be sized to allow the resilient tab to be pressed against the stem in a compressed configuration, as well as spaced from the stem in an extended configuration. The tip  158  of the resilient tab may form a ledge which moves the bolt catch of a firearm after the last ammunition cartridge has been removed from the magazine. The interior surface of the stem may include a curved surface  160  which forms a rear shroud for a portion of the magazine spring. 
     The port side wing  122  may extend downward and away from the port side surface of the follower. The port side wing  122  may be generally rectangular in shape. The port side wing may be relatively thin due to the confined space requirements of the magazine interior. The port side wing may be flexible and resilient. The starboard side wing  124  may be located opposite the port side wing  122  on the starboard side surface of the follower. The starboard side wing  124  may otherwise be similar in construction and resilience to its counterpart. The side wings of the follower may be visible in the windows  46  of the magazine. The bottom edge  162  or a marking on the side wings may cooperate with indicia around the window to indicate the number of ammunition cartridges in the magazine. 
     The lower surface  116  of the follower  14  may include an axial shank  164 , a leading cross shank  166 , and a trailing cross shank  168 . The leading cross shank may include a ledge  170  beneath the lower surface of the follower. The ledge  170  and the lower surface  116  of the follower  14  may cooperate to form a seat or spring attachment location for the magazine spring. The leading cross shank  166  and the trailing cross shank  168 , further may be configured and dimensioned to provide internal support for the magazine spring  16 . 
     Referring to  FIGS. 12 ,  22 A,  22 B,  22 C and  22 D, the magazine spring  16  may be a compression spring. In the exemplary embodiment, the magazine spring may be formed by a round wire coil that includes a small curve  172  separated from a larger curve  174  by a straight length  176 . As shown in  FIG. 22A , the wire may have a diameter D1 of approximately 1.5 mm. As shown in  FIG. 22D , the radius of the small curve (or small radius) R1 may be approximately 6.5 mm, and the radius of the larger curve (or large radius) R2 may be approximately 8.1 mm. The length of the coil measured from the end of the small curve to the end of the larger diameter curve (or maximum outer dimension of wire coil) L3 may be approximately 49.5 mm. 
     Referring back to  FIG. 22A , the wire may be right hand wound and have a pitch L2 of approximately 19 mm. The ends  240 ,  242  of the magazine spring may be squared. As shown in  FIG. 22E , one end of the magazine spring may terminate with an end segment having a length L4 of approximately 22.8 mm. This end  240  may be configured and dimensioned to connect with the floor plate  18 , as shown in  FIGS. 15-16  and described below. 
     Referring to  FIG. 22F , the other end of the spring  242  may terminate with a generally L-shaped segment having a dimension L5 of approximately 5.0 mm and a length L6 of approximately 37.5 mm. The other end  242  may be configured and dimensioned to connect to the follower  14 , as shown in  FIGS. 12-14  and described below. 
     In the embodiment shown in  FIGS. 22A-C , the magazine spring may include approximately 15 total coils. The magazine spring may have a free length of approximately 277 mm, and may possess a preloaded force of approximately 15 N (Newton) for a reference length of 180 mm. The solid height of the coil (or fully closed length) may be approximately 25.5 mm. The wire may be music wire as specified by ASTM A228. 
     A summary of a preferred magazine spring design for the 30 round magazine of  FIG. 1  is presented in Table 1. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Magazine Spring Design for a 30 Round Capacity Magazine 
               
             
          
           
               
                   
                   
                 Preferred 
                 Preferred 
                 Most  
               
               
                   
                 Variable/ 
                 Upper 
                 Lower 
                 Preferred 
               
               
                 Parameter 
                 Units 
                 Value 
                 Value 
                 Value 
               
               
                   
               
             
          
           
               
                 Outer Dimension (Wire) 
                 D1 (mm) 
                 — 
                 — 
                 1.5 
               
               
                 Free Length 
                 Ll (mm) 
                 — 
                 — 
                 277.0 
               
               
                 Pitch 
                 L2 (mm) 
                 — 
                 — 
                 19 
               
               
                 Outer Dimension (Coil) 
                 L3 (mm) 
                 49.8 
                 49.2 
                 49.5 
               
               
                 Length of Bottom End 
                 L4 (mm) 
                 23.1 
                 22.5 
                 22.8 
               
               
                 Length of Offset 
                 L5 (mm) 
                 5.3 
                 4.7 
                 5.0 
               
               
                 Length of Top End 
                 L6 (mm) 
                 37.8 
                 37.2 
                 37.5 
               
               
                 Small Radius 
                 R1 (mm) 
                 6.8 
                 6.2 
                 6.5 
               
               
                 Large Radius 
                 R2 (mm) 
                 8.4 
                 7.8 
                 8.1 
               
               
                 Offset Radius 
                 R3 (mm) 
                 2.5 
                 1.9 
                 2.2 
               
               
                 Reference Length 
                 RL (mm) 
                 — 
                 — 
                 180 
               
               
                 Preloaded Force 
                 PF (N) 
                 — 
                 — 
                 15 
               
               
                 Solid Height 
                 LFC (mm) 
                 — 
                 — 
                 25.5 
               
               
                 (or Full Close Length) 
               
               
                   
               
               
                 Notes: 
               
               
                 (a) Type of ammunition cartridge: 5.56 × 45 mm NATO or .223 Remington. 
               
               
                 (b) Type of wire: round wire per ASTM A228. 
               
             
          
         
       
     
     The general spring configuration of  FIGS. 22A-F  may be adapted for use in other magazines. For example, the magazine spring may be designed for an ammunition magazine that stores up to ten 5.56×45 mm ammunition cartridges. In one embodiment, a ten round capacity magazine may include a shortened and straighter casing, but which otherwise maintains features and components of the magazine of  FIG. 1 . In another example, the magazine spring may be adapted for use in an ammunition magazine cartridge that stores up to twenty 5.56×45 mm ammunition cartridges. In yet another example, the magazine spring may be adapted for use in an ammunition magazine cartridge that stores up to thirty five, forty five, or fifty 5.56×45 mm ammunition cartridges. 
     Table 2 presents a preferred magazine spring design for an ammunition magazine that may store and feed an AR15 type rifle with up to ten 5.56×45 mm ammunition cartridges. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Magazine Spring Design for a 10 Round Capacity Magazine 
               
             
          
           
               
                   
                   
                 Preferred 
                 Preferred 
                 Most  
               
               
                   
                 Variable/ 
                 Upper  
                 Lower 
                 Preferred 
               
               
                 Parameter 
                 Units 
                 Value 
                 Value 
                 Value 
               
               
                   
               
             
          
           
               
                 Outer Dimension  
                 D1 (mm) 
                 — 
                 — 
                 1.5 
               
               
                 (Round Wire) 
                   
                   
                   
                   
               
               
                 Free Length 
                 Ll (mm) 
                 — 
                 — 
                 180.5 
               
               
                 Pitch 
                 L2 (mm) 
                 — 
                 — 
                 19 
               
               
                 Outer Dimension (Coil) 
                 L3 (mm) 
                 49.8 
                 49.2 
                 49.5 
               
               
                 Length of Bottom End 
                 L4 (mm) 
                 23.4 
                 22.8 
                 23.1 
               
               
                 Length of Offset 
                 L5 (mm) 
                 5.3 
                 4.7 
                 5.0 
               
               
                 Length of Top End 
                 L6 (mm) 
                 37.8 
                 37.2 
                 37.5 
               
               
                 Small Radius 
                 R1 (mm) 
                 6.4 
                 5.8 
                 6.1 
               
               
                 Large Radius 
                 R2 (mm) 
                 8.4 
                 7.8 
                 8.1 
               
               
                 Offset Radius 
                 R3 (mm) 
                 2.5 
                 1.9 
                 2.2 
               
               
                 Reference Length 
                 RL (mm) 
                 — 
                 — 
                 75.0 
               
               
                 Preloaded Force 
                 PF (N) 
                 — 
                 — 
                 15 
               
               
                 Solid Height 
                 LFC (mm) 
                 — 
                 — 
                 20.0 
               
               
                 (or Full Close Length) 
               
               
                   
               
               
                 Notes: 
               
               
                 (a) Type of ammunition cartridge: 5.56 × 45mm NATO or .223 Remington. 
               
               
                 (b) Type of wire: round wire per ASTM A228. 
               
             
          
         
       
     
     The foregoing spring designs are believed to have important operational benefits, such as providing greater spring force at the front of the follower due to the smaller radius at the front end of the coil. Larger spring forces at the front end of the coil may promote reliable feeding of ammunition cartridges from the magazine by overcoming any added local resistance at the front of the casing that may be generated by the interaction of the ammunition cartridges and multi-faceted block. Moreover, larger spring forces at the front end of the coil may provide for a firmer squeeze of the ammunition cartridges near the top of the magazine. This may advantageously position and secure the ammunition cartridges near the top of the magazine, as described in more detail below. Also, larger spring forces at the front end of the coil may promote reliable feeding of ammunition cartridges from the magazine as the quantity of stored ammunition cartridges run low because the attitude of the front end of the follower may be more likely to remain in a neutral or elevated position as the magazine spring approaches the limits of its working length. 
     Accordingly, the benefits of the foregoing spring designs may be captured and extended by maintaining the general configuration of the magazine spring designs of Table 1 and Table 2 by examining the relationship between the smaller radius and larger radius of the wire coil. This relationship may be described, in part, by a “coil ratio” (or CR), which may be calculated by dividing the larger radius of the wire coil by the smaller radius of the wire coil. For example, the coil ratio of the most preferred magazine spring design presented in Table 1 (where the smaller radius is 6.5 mm and the larger radius is 8.1 mm) is approximately equal to 1.25 (i.e., 8.1/6.5). Likewise, the coil ratio of the most preferred magazine spring design presented in Table 2 (where the smaller radius is 6.1 mm and the larger radius is 8.1 mm) is approximately equal to 1.33 (i.e., 8.1/6.1). 
     Table 3 presents coil ratio calculation results for the preferred and most preferred values of the spring designs of Table 1 and Table 2. 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Coil Ratios (CRs) for the Spring Designs of Tables 1 and 2 
               
             
          
           
               
                   
                   
                 R2 (mm) 
               
             
          
           
               
                   
                   
                 7.8 
                 7.9 
                 8.0 
                 8.1 
                 8.2 
                 8.3 
                 8.4 
               
               
                   
               
             
          
           
               
                 R1 (mm) 
                 5.8 
                 1.34  
                 1.36 
                 1.38 
                 1.40 
                 1.41 
                 1.43 
                 1.45 
               
               
                   
                 5.9 
                 1.32  
                 1.34 
                 1.36 
                 1.37 
                 1.39 
                 1.41 
                 1.42 
               
               
                   
                 6.0  
                 1.30  
                 1.32 
                 1.33 
                 1.35 
                 1.37 
                 1.38 
                 1.40 
               
               
                   
                 6.1 
                 1.28  
                 1.30 
                 1.31 
                 1.33 
                 1.34  
                 1.36 
                 1.38 
               
               
                   
                 6.2 
                 1.26 
                 1.27  
                 1.29 
                 1.31 
                 1.32  
                 1.34 
                 1.35 
               
               
                   
                 6.3 
                 1.24 
                 1.25 
                 1.27 
                 1.29 
                 1.30 
                 1.32 
                 1.33 
               
               
                   
                 6.4 
                 1.22  
                 1.23 
                 1.25 
                 1.27 
                 1.28 
                 1.30 
                 1.31 
               
               
                   
                 6.5 
                 1.20  
                 1.22 
                 1.23 
                 1.25 
                 1.26 
                 1.28  
                 1.29 
               
               
                   
                 6.6 
                 1.18 
                 1.20 
                 1.21 
                 1.23 
                 1.24  
                 1.26 
                 1.27 
               
               
                   
                 6.7 
                 1.16 
                 1.18 
                 1.19 
                 1.21 
                 1.22 
                 1.24  
                 1.25 
               
               
                   
                 6.8 
                 1.15 
                 1.16 
                 1.18 
                 1.19 
                 1.21 
                 1.22 
                 1.24 
               
               
                   
               
             
          
         
       
     
     As shown in Table 3, the CR values for the preferred Small Radius and Large Radius values of the spring design of Table 1 range from approximately 1.15 to approximately 1.35. The CR value for the most preferred Small Radius and Large Radius values of the spring design of Table 1 is approximately 1.25. By comparison, the CR values for the preferred Small Radius and Large Radius values of the spring design of Table 2 range from approximately 1.22 to approximately 1.45. The CR value for the most preferred Small Radius and Large Radius values of the spring design of Table 2 is approximately 1.33. 
     The combined range of CR values for the preferred Small Radius and Large Radius values of the spring designs of Table 1 and Table 2 range from approximately 1.15 to approximately 1.45. These CR values reflect magazine spring coil configurations that provide suitable operation of two ammunition magazines constructed in accordance with aspects of the present invention. 
     The shared range of CR values for the spring designs of Table 1 and Table 2 range from approximately 1.22 to approximately 1.35. The CR values for the most preferred Small Radius and Large Radius values of the spring designs of Table 1 and Table 2 are contained within the shared range of CR values These CR values reflect magazine spring coil configurations that provide enhanced operation of two ammunition magazines constructed in accordance with aspects of the present invention. 
     Magazine springs for small arms weapons, however, generally may have a small radius R1 that ranges from approximately 3 mm to approximately 7 mm and a large radius R2 that ranges from approximately 5 mm to approximately 9 mm, as long as the larger radius R2 is greater than the small radius R1. Hence, CR values for a magazine spring for many small arms weapons generally may be greater than 1 and less than approximately 3. 
     Moreover, in view of foregoing, CR values for a magazine spring for a small arms weapon preferably may be at least 1.05. More preferably, CR values a magazine spring for a small arms weapon may range from approximately 1.10 to approximately 1.50. Most preferably, CR values for a magazine spring for a small arms weapon may range from approximately 1.20 to approximately 1.35. In the embodiment of the magazine spring design of Table 1, the optimum RV value is approximately 1.25. In the embodiment of the magazine spring design of Table 2, the optimum RV value is approximately 1.32. 
     Although the spring designs of Table 1 and Table 2 are believed to have important operational benefits, other wire types, dimensions, or configurations may be used provided the alternate magazine spring design provides reliable operation of the magazine. 
     Referring to  FIGS. 36A-L , the magazine spring may be formed from round, shaped, or stranded wire. Round wire  248  may have a circular cross section  250  ( FIG. 36A ). Typically, round wire diameters may range from 0.10 mm to 16 mm. 
     Referring to  FIGS. 36B-J , shaped wire  252  may be defined as wire with a cross-sectional shape other than round, which may be produced by cold rolling. Typical shapes may include oval  254  ( FIG. 36B ), square  256  ( FIG. 36C ), rectangular  258  ( FIG. 36B ), trapezoid (or “keystone”)  260  ( FIG. 36E ), sharp triangle  262  ( FIG. 36F ), wedge  264  ( FIG. 36G ), equilateral triangle  266  ( FIG. 36H ), pie  268  ( FIG. 36I ), and half round  270  ( FIG. 36J ). The solid height of a shaped wire may be less than that of a similar round wire spring. Also, using chrome silicon shaped wire rather than traditional carbon steel material may produce a spring that can withstand additional shock and heat. 
     Referring to  FIGS. 36K and 36L , stranded wire  272  may be formed from several strands of wire (e.g., three to seven strands of wire) that are machine-twisted or woven around each other  274  ( FIG. 36K ), or around one wire that serves as a core  276  ( FIG. 36J ), to form a single strand. The stranded wire may be made of music wire, rocket wire or other suitable material. Stranded wire springs may be well suited to repetitive impact loading conditions and may provide a long life cycle for the spring. 
     Spring materials may be high strength alloys having a Young&#39;s Modulus, E, ranging from approximately 190×10 3  MPa at standard temperature and pressure. Suitable spring wire may include carbon steel wire, including without limitation music wire. Preferably, the music wire may conform with ASTM A228. Alloy steel wire, such as chrome silicon wire, as well as other materials may be used. 
     Additionally, the magazine spring of  FIG. 22A  may be designed for use with ammunition magazines that store 5.45×51 mm ammunition cartridges, 5.45×39 mm ammunition cartridges, 7.62×54 mm ammunition cartridges; 7.62×51 mm ammunition cartridges, 7.62×39 mm ammunition cartridges; .308 Winchester ammunition cartridges; and other ammunition cartridges. The casing and other magazine components may need to be adjusted for these applications as well. For instance, the magazine casing may need to be modified for weapon compatibility. For example, the magazine of  FIG. 1  may be tailored for compatibility with the following non-limiting list of small arms weapons: AR-15, M16, M4, M249, LSAT, HK416, AK-47, and Negev LMG. 
     Referring to  FIGS. 7 and 8 , the magazine spring  16  may be secured to the follower at the seat  178  formed by the ledge  170  on the leading cross shank and the opposing lower surface  116  of the follower. 
     Referring to  FIG. 15 , the floor plate  18  may include an upper surface  180  and lower surface  182 . The upper surface of the base plate may include an axial wall  184 . The axial wall  184  may include an upper side  186  that is spaced from the upper surface of the floor plate. The upper side  186  of the axial wall may have a length that is shorter than the axial shank  164  of the follower. The axial wall may include a front side  188  that extends from the front of the top surface to the upper surface  180  of the floor plate. Additionally, the axial wall may include a rear side  190  that extends from the rear of the top surface to the upper surface  180  of the floor plate. The front side  188  of the axial wall may include a notch  192  near the upper surface  180  of the floor plate. The front notch  192  may be configured and dimensioned to receive and secure a spring wire. The rear side  190  of the axial wall may include a notch  194  near the upper surface of the floor plate. The rear notch  194  may be configured and dimensioned to receive and secure a spring wire. The axial wall may include side buttresses  196 ,  198 . The side buttresses may each include a side notch  200 ,  202  for receiving and securing the magazine spring  16 . As shown in  FIGS. 7 and 9 , the lower end of the magazine spring  16  may be secured to the floor plate at four magazine spring attachment points. Two attachment points may be notches  192 ,  194  near the base of the axial wall, and two attachment points may be notches  200 ,  202  near the base of each buttress. 
     Referring to  FIGS. 9 ,  16 , and  17 , the lower side  182  of the floor plate  18  may include a planar surface  204  and a raised area  206  that extends away from the planar surface. The raised area  206  may include a flat upper surface  208  and a sidewall  210  extending from the upper surface to the lower side of the floor plate. The raised area may be formed in a button shape. The upper surface of the raised area may include a concave surface  212 . The upper side  180  of the floor plate and the lower side  182  of the floor plate may have different lengths. For example, the length of the upper side may be greater than the length of the lower side. The rear end of the floor plate may taper from a longer upper surface to a shorter lower surface to form a projection  214 . 
     Referring to  FIG. 18 , the base may include an elongated plate  216 . The elongated plate may include a front side  218 , a rear side  220 , and lateral sides  222  between the front and rear sides. The base may further include a side wall  224 . The side wall  224  may surround the elongated plate on three sides. For example, the side wall may surround the elongated plate on the front and lateral side. Referring to  FIGS. 16 and 17 , the side wall may include a groove  226 . The groove  226  may be configured and dimensioned to slide on to the housing flange  106 . Each end of the side wall may include an attachment structure  228 , such as a lever, which is configured and dimensioned to form a mechanical joint with the housing. For example, the lever  228  and housing ledge  106  may form a snap-fitting. Preferably, the snap-fitting is a releasable joint. 
     Referring to  FIGS. 17 and 18 , the elongated plate  216  may include an interior surface  230  and an exterior surface  232 . The interior surface  230  may include a notch  234 . The notch  234  may include an end wall  236 . The end wall may include an opening  238  which extends to the exterior surface  232  of the plate. The notch  234  may be configured and dimensioned to mate with the raised area on the floor plate. 
     Referring to  FIG. 7 , the magazine may have an unloaded configuration in which the follower  14  may be disposed in the housing  12  such that the front bumper  118  faces the front wall of the housing, the lower portion of the resilient tab  152  may be in the channel  156  on the rear side  52  of the housing, and the tip of the resilient tab  158  may be positioned above the rear sill  64 . Additionally, the starboard side bumper  148  may press against the lower surface  96  of the multi-faceted block on the starboard side  56  of the housing, and the port side bumper  146  may press against the lower surface  96  of the multi-faceted block on the port side of the housing. Moreover, the spacer  132  may press against the starboard side magazine feed lip  30 . The magazine spring  16  may exert a force of approximately 15 N on the follower  14 . The magazine spring  16  also may exert an opposite force of approximately 15 N on the floor plate  18 . The raised area  206  on the lower surface of the floor plate may be disposed in the notch  234  on the interior surface of the base plate, and the base plate groove  226  may be interlocked with the housing flange  106 . 
     Referring to  FIG. 12 , the front bumper  118  may be spaced from the front wall  50  of the housing, the resilient tab  154  may be disposed in the channel  156  on the rear wall of the housing, and the top of the magazine spring  16  may be secured to the leading cross shank  166  and contained within the front shroud  150 , rear shroud  160 , starboard side wing  124 , and port side wing  122 . 
     Referring to  FIG. 13 , the starboard side bumper  148  and port side bumper  146  are disposed in the starboard side bumper track  76  and port side bumper track  76 , respectively. The stem  152  of the resilient member may be disposed in the channel  156  on the rear sidewall  52  of the housing, and the rear bumper  120  may be disposed against the rear side wall  52  of the housing. The top of the magazine spring may be secured to the leading cross shank  166  and contained within the front shroud  150 , rear shroud  160 , starboard side wing  124 , and port side wing  122 . 
     Referring to  FIGS. 8 ,  9 , and  10 , ammunition cartridges  24  may be loaded into the magazine  10 . As shown in  FIG. 10 , the ammunition cartridges  24  may be stacked in two columns on the follower  14 . The port side row of ammunition cartridges may generally rest on the upper surface  114  and the starboard side row of ammunition cartridges rest on the cartridge spacer  132 . The cartridge  24  nearest the top of the magazine is retained by the magazine feed lip  30  on the starboard side of the housing. Referring to  FIG. 8 , the starboard bumper  148  is disposed in the starboard bumper track  76  and the starboard facing sides of the ammunition cartridges are pressed against ammunition cartridge guide surfaces  78 ,  80 ,  82 . Referring to  FIG. 9 , as the magazine reaches full capacity the follower  14  approaches the base  20  of the magazine. When the magazine is fully loaded with ammunition cartridges (i.e., in the fully loaded configuration), the axial shank  164  or cross shanks  166 ,  168  of the follower rest on top of the axial wall  186 . This blocks over compression of the magazine spring  16  because the solid height of the spring is less than the distance from the spring attachment points  192 ,  194 , 200 ,  202  on the upper surface of the floor plate to the spring attachment point  170  under the lower surface of the follower. In another embodiment, the front bumper  118  and rear bumper  120  of the follower  14  also rest on the floor plate  18  in the fully loaded configuration. The bottom ammunition cartridge has been removed from  FIGS. 8 and 9  to generally illustrate the relation between the features of the ammunition cartridges and the ammunition cartridge guide surfaces. 
     The magazine components (other than the spring) may be formed from a polymer material. For example, the housing may be formed from an injection molded polymer (e.g., polyamide, polyphthalamide (PPA), or poly aryl ether ketone (PEK)). Preferably, the housing may be formed from polyamide nylon 6,6. Additionally, the polymer matrix may include reinforcement fibers (e.g., carbon-fiber or glass-fiber). Although polymer or reinforced polymer materials may be preferred for forming the magazine components, other materials that are sufficiently strong and durable may be used. For example, the magazine components may be manufactured from aircraft quality aluminum, titanium, steel or other alloys. Also, magazine components may be formed by over molding a second material over a base part. For example, an elastomer (e.g., rubber), may be over molded on to a component formed from carbon-fiber reinforced polymer. Accordingly, the fore grip and rear grip portions of the housing may be formed from rubber that is molded on top of a carbon-fiber reinforced polymer material. 
     Referring to  FIG. 35 , the follower  14  may include one or more markings  278  (e.g., a line, an arrow, dot, triangle, visual target, or illuminated feature) which are visible through one (or both) window(s)  46  in the magazine casing  12 . The marking(s)  278  may cooperate with the indicia  48  on the sides of the window  46  to indicate the number of ammunition cartridges  24  in the magazine. For example, the marking  278  may be a line that points to a tick mark  48   a  along a numerical scale that is positioned on the side of the window to provide a visual indication of the number of ammunition cartridges  24  in the magazine. 
     In use, a loaded magazine  10  ( FIG. 35 ) may be inserted into the magazine well  280  of a small arms weapon  22  such as an M4, M-16, or AR-15 type firearm (see e.g.,  FIG. 3 ). As the weapon  22  is charged ( FIGS. 29-31 ), the bolt carrier  282  may advance between the magazine feed lips and the bolt  284  may push the uppermost ammunition cartridge  24  forward, inward, and upward over the front sill  62  of the magazine toward the barrel extension  290  and firearm chamber  286 . As described below, the tapered concave upper surface  88  of the multi-faceted block and adjacent front sidewall of the magazine, as well as the guide surfaces  98 ,  100 ,  102  on the magazine feed lips  30 ,  32  are configured to stabilize and direct the transfer of ammunition cartridges to the firearm chamber ( FIGS. 23-28 ). 
     As the uppermost ammunition cartridge is transferred from the magazine, the magazine spring pushes the follower upward to position the next ammunition cartridge for feeding ( FIG. 32 ). As each ammunition cartridge advances up the magazine, the ammunition cartridge encounters the angled and tapered rear surface  94  that is configured to push the ammunition cartridges backward (e.g.,  FIGS. 23 ,  25  and  29 ). Shortly thereafter, the ammunition cartridge  24  will encounter the angled subsurface  92 , which is configured to push the front of the ammunition cartridge inward ( FIGS. 23 ,  26  and  27 ). The tip of the ammunition cartridge may move inward by a distance L7 of approximately 1 mm ( FIG. 27 ). 
     As the ammunition cartridge  24  rises above the edge of the angled and tapered rear surface  94 , the pressure from the multi-faceted block  86  is removed ( FIGS. 23 and 28 ) and the front tip of the ammunition cartridge may shift outward by approximately 1 mm, and settle on top of the tapered concave upper surface  88 . Additionally, the ammunition cartridge may shift forward, and move upward and inward under the direction of the tapered concave upper surface  88 , adjacent front sidewall of the magazine, and adjacent ammunition cartridges or follower to an improved position for feeding into the barrel extension  290  and chamber  286  ( FIGS. 23 ,  24 ,  28  and  29 ). After the final ammunition cartridge in the magazine has been fired  24   f , the resilient tab  158  may rise above the rear sill  64  to move the bolt catch  288  in position to block forward travel of the bolt  284  ( FIG. 34 ). 
     As shown in  FIG. 24 , the ammunition cartridges  24   b ,  24   c  near the uppermost ammunition cartridge  24   a  may be increasingly compressed between the lower stack of ammunition cartridges and/or the follower  14 , the multi-faceted block  86  and the magazine casing side walls  52 ,  54 . Squeezing the ammunition cartridges  24   b ,  24   c ,  24   d ,  24   e  and  24   f  in this manner may provide a compact arrangement which forms a stable, secure mass that acts as another guide surface for the uppermost ammunition cartridge  24   a . Thus, the compact arrangement of ammunition cartridges may provide a stable bottom guide for the upper most ammunition cartridge. Also, pressure applied on the uppermost ammunition cartridge  24   a  by the adjacent ammunition cartridges  24   b ,  24   c  may help drive the uppermost ammunition cartridge upward as it is pushed forward by the bolt. 
     A compact, stable, and secure arrangement of ammunition cartridges near the top of the magazine may prevent (or limit) uncontrolled movement or jostling of the ammunition cartridges, which may result from firing recoil, recoil travel of the bolt assembly, or external impacts to the magazine or weapon. This may reduce the likelihood of a misfeed or jamming of the weapon. 
     The magazine spring of  FIG. 22A  may facilitate reliable feeding of the ammunition cartridges to the firearm chamber because the relatively stronger spring forces applied to the front of the follower  14  may help the ammunition cartridges smoothly overcome the restriction caused by the multi-faceted block. Relatively stronger spring forces at the front of the follower may compact the nearby ammunition cartridges against the casing side walls to form a more stable and secure mass. Relatively stronger spring forces applied to the front of the follower also may help maintain the front of the follower in a favorable position for traveling through the magazine and feeding the uppermost cartridge to the weapon. Further relatively stronger spring forces applied to the front of the follower may better resist impacts from firing recoil and return travel of the bolt carrier. The resilient follower wings  122 ,  124  and resilient rear tab  154  may provide a degree of freedom of movement and resistance within the magazine casing to further accommodate impacts and promote proper positioning of the ammunition cartridges for feeding to the firearm. 
     While it has been illustrated and described what at present are considered to be a preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the invention. For example, the magazine may be formed with a smaller ammunition capacity or different spring design to accommodate different types of ammunition cartridges. Likewise, the configuration of the magazine casing may be modified for compatibility with other small arms weapons. Additionally, features and/or elements from any embodiment may be used singly or in combination with other embodiments. Therefore, it is intended that this invention not be limited to the particular embodiments disclosed herein, but that the invention include all embodiments falling within the scope and the spirit of the present invention.