Abstract:
Ammunition cartridges for hunting big game with an AR15 rifle are provided while maintaining a size of the ammunition cartridge that permits multiple ammunition cartridges to be inserted into an AR15 rifle magazine in alternating side by side relation. Each cartridge has a rim diameter of 0.422 inches, extractor groove and a slight tapered main body base of 0.36°. In one embodiment, the main base body extends to form a cartridge with total length of 1.8 inches and nominal body taper of 0.020 inches to accept a bullet with a diameter of 0.400 inches. In other embodiments, the main body base extends to a shoulder and a neck to form a cartridge with a total length of 1.66 inches. The shoulder tapers to the neck at a 35° angle with a nominal body taper of 0.014 inches. These embodiments accept bullets with diameters of 0.277, 0.284 and 0.308 inches.

Description:
FIELD OF THE INVENTION 
     The subject system generally relates to the field of ammunition for firearms. Further, the subject concept is directed to the field of ammunition cartridges which may be used for varying bullet calibers in a variety of scenarios, but in particular, is useful for big game hunting. Still further, the subject concept is directed to the field of adapting and fabricating ammunition cartridges which accept differing bullet calibers. Still further, this concept is directed to the field of big game hunting which is adapted to a wide range of rifles and in particular, to ammunition cartridges for an AR15 type rifle, such as the AR15 rifle, the M16 rifle and other variants. 
     Still further, this concept is directed to the area of providing an ammunition cartridge which may be sized to allow alternate side-by-side stacking of the cartridge in a standard AR15 type rifle magazine or other rifle magazine having substantially the same dimensions as an AR15 type rifle magazine. Still further, this concept is directed to the field of providing ammunition cartridges which are adaptable to a selected group of bullets having particular caliber and weight which increases the firepower of a firearm to provide impact energy greater than that known in the prior art for particular firearms, while maintaining the ability to have a standard magazine accept the combination of ammunition cartridges in a side-by-side alternating manner. 
     Still further, the subject matter of the subject ammunition cartridge is directed to the area of reducing the overall length of an ammunition cartridge for acceptance into a standard AR15 type rifle magazine while maintaining the acceptable impact energy and muzzle energy acceptable for big game hunting. 
     SUMMARY OF THE INVENTION 
     There is provided an ammunition cartridge which includes an annularly contoured rim section defining an axis line and having an outer diameter of 0.422 inches (within manufacturing tolerance ranges). The annularly contoured rim section has two opposing ends, namely, first and second ends with the first end of the annularly contoured rim section adapted to receive a standard small or large rifle primer. An extractor groove is formed adjacent the rim second end and the extractor groove has an outer diameter less than the outer diameter of the annularly contoured rim section. 
     A hollow main body section is adapted to receive a powder charge where the main body section is symmetrically contoured about the axis line and extends in the axis line direction from the extractor groove and has a main body first end which is next to or adjacent to the extractor groove. An opposing main body second end is adapted to receive a particular caliber bullet with the hollow main body section contoured to taper inwardly toward the axis line from the rim section throughout at least a portion of the length of the hollow main body at an angle of 0.36° (within manufacturing tolerance ranges). 
     It is an object of the present invention to provide an improved ammunition cartridge for a firearm. 
     It is another object of the subject invention to provide an improved ammunition cartridge, particularly sized and dimensioned to be accepted in an AR15 type rifle. 
     It is a further object of the invention to provide an improved ammunition cartridge for an AR15 type rifle, which provides increased muzzle energy without substantially increasing the size and overall length of the ammunition cartridge. 
     Still further, it is an object of the invention to provide an improved ammunition cartridge for an AR15 type rifle which has high durability. 
     A still further object of the invention is to provide an improved ammunition cartridge for an AR15 type rifle that improves projectile or bullet energy over extended ranges. 
     It is a further object of the subject invention to provide an ammunition cartridge which may be used in combination with a plurality of cartridges to be inserted into a standard AR15 type rifle magazine. 
     It is a further object of the subject invention to provide an ammunition cartridge which may be stacked in an alternating side-by-side relation to maintain the standard capacity of a standard AR15 type rifle magazine. 
     It is a further object of the subject invention to provide an improved ammunition cartridge which is sized in a manner to increase the powder charge volume of an ammunition cartridge to provide increased muzzle energy and impact energy. 
     A further object of the subject invention is to provide an ammunition cartridge which permits the standard AR15 type rifle to be used in big game hunting. 
     A further object of the invention is to utilize an existing AR-15 bolt variant that is commercially available. Currently, AR-15 type rifles utilize bolts that accommodate ammunition cartridges with rim diameters of 0.378 inches, 0.422 inches, 0.445 inches and 0.473 inches. As the bolt face is made larger to accommodate ammunition cartridges with larger rim diameters, the locking lugs become progressively weaker. The inventors have chosen to use the AR-15 bolt that accommodates an ammunition cartridge with a 0.422 inch rim diameter. It is a known fact that the locking lugs on AR-15 type bolts fatigue over time and will eventually fail. By utilizing the 0.422 inch rim diameter the inventors have developed an ammunition cartridge to be used with known bolts for the AR-15 that enhances balance between bolt durability and ammunition performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the ammunition cartridge of the subject concept; 
         FIG. 2  is an elevational view of the subject ammunition cartridge including in combination the bullet inserted therein; 
         FIG. 3  is an elevational view of an embodiment of the subject ammunition cartridge; and, 
         FIG. 4  is a schematic elevational view of a plurality of cartridges mounted in a standard firearm magazine permitting side-by-side alternating positioning. 
     
    
    
     PRIOR ART 
     Numerous ammunition cartridges are known in the art. An example of a prior art cartridge is the standard cartridge known as the 5.56 NATO/.223. An acceptable hunting load for this cartridge would be a 60 grain jacketed soft point bullet having a 0.224 inch diameter. At a muzzle velocity of 3125 fps, this configuration yields a 1300 foot pound force at the muzzle, but the energy drops off to 973 foot pounds at 100 yards and 514 foot pounds at 300 yards. 
     When a prior art cartridge, such as the 5.56 NATO/.223 cartridge, is adapted to have a larger neck or “necked up” to accept a larger bullet, the powder charge is reduced. However, this trade-off does not yield higher impact energy at the target. 
     In the many ammunition cartridges available, options are provided where the ammunition cartridge may be increased in size and dimension to accept a larger diameter bullet with a powder charge. Increasing the size of the cartridge decreases the amount of ammunition cartridges that may be loaded into a magazine due to the fact that larger diameter ammunition cartridge can no longer be double-stacked in an alternating side-by-side manner in AR-15 rifle magazines. The concept of alternating side-by-side stacking of ammunition cartridges into a standard magazine, maintains the maximum efficiency of the original AR-15 magazine design. Ammunition cartridges with rim and base diameters greater than 450 inches do not reliably double stack in a standard AR-15 magazine. 
     Other prior art ammunition cartridges used in big game hunting scenarios generally have a longer overall length, which are not adaptable to an AR15 type rifle. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIGS. 1-2 and 4 , there is provided an ammunition cartridge  10  to accommodate insertion thereof of a bullet  12  to be used in conjunction with a hunting rifle. The subject ammunition cartridge  10  is adaptable for insertion of bullets  12  of varying calibers, however, the most common calibers being used for big game hunting generally are 270, 280, and 300. In addition, the subject ammunition cartridge can use a 0.40 in/10 mm caliber bullet. The aforementioned calibers are commonly referred as .270, 7 mm, .30 and .40 caliber. Although useful for big game hunting, ammunition cartridge  10  may be used in a variety of hunting arenas. In general, big game hunting is directed to large animals sought and harvested by hunters and although the term “big game” is not well-defined, it is generally accepted in North America as referring to deer, antelope, sheep, black bears, and elk, among other large animals. Differing regions have particular statutes and regulations requiring minimum calibers and minimum bullet energies at the muzzle for rifles and handguns used for big game hunting. In general, an acceptable big game hunting ammunition cartridge should develop 1200-1500 foot pounds of energy at the intended target, at any given range. 
     One of the problems associated with hunting big game with AR-15-type rifles, is that the bullets  12  do not have sufficient muzzle energy or sufficient impact energy at the intended target. Thus, most prior art ammunition cartridge variants for the AR-15-type rifles have not been capable of producing the aforementioned 1200-1500 foot pounds of energy at the intended target. 
     The subject ammunition cartridge  10  has been developed to accommodate a standard caliber bullet while providing sufficient powder charge that the impact energy and muzzle energy is sufficient to meet preferred standards for big game hunting. The problem associated with the use of AR15-type rifles for big game hunting is the fact that prior art ammunition cartridges and their inserted bullets do not generally provide for sufficient muzzle and impact energy at the intended target at any given range. Still further, when standard ammunition cartridges with a base and rim diameter greater than 0.450 inches are used, they are not able to be reliably inserted into a standard AR15 type rifle magazine in an alternating side-by-side relation. As will be seen in following paragraphs, the particular contouring and sizing of the subject ammunition cartridge  10  obviates the disadvantages associated with prior ammunition cartridges now in use. 
     Referring once again to  FIGS. 1 and 2 ,  FIG. 1  shows the ammunition cartridge  10  and  FIG. 2  shows the ammunition cartridge  10  having inserted therein bullet  12 . Ammunition cartridge  10  includes annularly contoured rim section  14  adapted to have a primer  16  inserted therein. The overall configuration of ammunition cartridge  10  is circular in cross-section, as is common in the art. Annularly contoured rim section  14  is developed about axis line  18 , as is seen in  FIGS. 1-3 . Annular rim section  14  has an outer diameter of 0.422 inches (within manufacturing tolerance ranges). 
     An extractor groove  22  is formed adjacent to rim second end  24  which is opposite annular rim section first end  26 , as is seen in the Figures. Extractor groove  22  has a diameter less than the outer diameter of annular rim section  14 . For purposes of the subject ammunition cartridge  10 , the extractor groove  22  includes a diameter with respect to axis line  18  of 0.350 inches (within manufacturing tolerance ranges). Formed in one-piece formation to annular rim section  14  is hollow main body section  28  which is comprised of a main body first section  30 , a shoulder section  32 , and a neck section  34 . Hollow main body section  28  is adapted to receive a powder charge and the hollow main body section  28  is formed about the axis line  18  in a symmetrical manner. Hollow main body section  28  extends in the direction of axis line  18  from the extractor groove  22 . Hollow main body section  28  includes main body section first end  36  adjacent and formed in one-piece formation with extractor groove  22  and annular rim section  14 , and has an opposing main body section second end  38  from the main body section first end  36  toward main body section second end  38  tapered at an angle of 0.36° with a nominal body taper of 0.014 inch taper (all within manufacturing tolerance ranges). Main body second section end  38  has a diameter of 0.434 inches resulting in the 0.014 inch tapering at the tapering angle of 0.36°. 
     Main body first section  30  terminates in main body section second end  38  and is formed in one-piece formation with shoulder section  32 . Shoulder section  32  is tapered at a 35° angle with respect to axis line  18 , as is seen in  FIG. 2 . Shoulder section  32  tapers to be formed in one-piece formation with neck section  34  having a diameter ranging between 0.307 inches and 0.338 inches dependent upon the caliber size of bullet  12 . In general, for a 270 caliber bullet, the neck diameter is 0.307, for a bullet caliber of 280, the neck diameter is 0.314 inches, and for a 300 caliber bullet, the neck diameter is 0.338 inches (all within manufacturing tolerance ranges). The length of neck section  34  ranges between 0.28 inches-0.302 inches, dependent upon the bullet  12  caliber. The overall criteria is that the length of ammunition cartridge  10  from annular rim section first end  26  to neck second end  42  be maintained at a length of 1.66 inches. Thus, for differing caliber bullets, the sizing and dimensions of the neck section  34  and shoulder section  32  will be selected, dependent upon the bullet caliber being 270, 280, or 300. 
     Thus, it is seen in  FIGS. 1 and 2  that ammunition cartridge  10  comprises distinct section areas including annular rim section  14 , hollow main body section  28  comprised of main body first section  30 , shoulder section  32 , and neck section  34 . 
     By providing a taper angle of 35° for the shoulder section  32 , there is provided an increased charge chamber volume to accommodate a larger powder charge. Additionally, for standard caliber bullets  270 ,  280 , and  300 , the diameter of main body first section is tapered from a maximum of 0.448 inches at main body section first end  36  to a diameter of 0.434 inches developed at main body section second end  38 . 
     In this manner, as is seen in  FIG. 4 , a plurality of ammunition cartridges  10  may be inserted into a standard AR15 type rifle magazine  48 . Follower  50 , which is generally spring-loaded, biases the ammunition cartridges  10  to an upper section, as seen. With the particular novel dimensioning and the rising of ammunition cartridge  10 , cartridges  10  can be mounted in alternating side-by-side relation to provide the user with additional rounds in keeping with that which is known in the prior art. 
     The neck diameter of ammunition cartridge  10  is governed by a desired bullet diameter. Given a desired bullet diameter, the applicant has found that the length of the shoulder section  32  in relation to the overall length of the cartridge  10  is governed by the equation: 
                     L   s     =         S   r     -     N   r         tan   ⁢           ⁢     θ   s                 (   1   )               
where L s  is the length of the shoulder section  32  in inches between main body section  38  and neck end  42 , S r  is the radius of the cartridge  10  in inches at main body section  38  where the main body section  38  of the cartridge  10  meets the shoulder section  32 , N r  is the radius of the neck section  34  in inches and θ s  is the shoulder angle in degrees.
 
     With the overall length of the cartridge  10 , L c , being 1.66 inches, the length of the neck section  34 , L n , is determined by subtracting the base length of the cartridge  10  from the rim section  14  to the shoulder section  32 , L b , and the length of the shoulder section  32 , L s , from the overall length of the cartridge  10 , L c , wherein L n  is:
 
 L   n   =L   c   −L   b   −L   s .  (2)
 
     The general dimensions of ammunition cartridge  10  as fabricated are shown in Table 1 for differing bullet calibers. 
     
       
         
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                   
                 Cartridge 
               
             
          
           
               
                   
                 270 
                 280 
                 300 
               
             
          
           
               
                   
                 in. 
                 mm 
                 in. 
                 mm 
                 in. 
                 mm 
               
               
                   
               
             
          
           
               
                 Bullet Diameter 
                 0.277 
                 7.0358 
                 0.284 
                 7.2136 
                 0.308 
                 7.8232 
               
               
                 Rim Diameter 
                 0.422 
                 10.71 
                 0.422 
                 10.71 
                 0.422 
                 10.71 
               
               
                 Base Diameter 
                 0.448 
                 11.3792 
                 0.448 
                 11.3792 
                 0.448 
                 11.3792 
               
               
                 Neck Base Diameter 
                 0.307 
                 7.7978 
                 0.314 
                 7.9756 
                 0.338 
                 8.5852 
               
               
                 Rim to Base 
                 0.2 
                 5.08 
                 0.2 
                 5.08 
                 0.2 
                 5.08 
               
             
          
           
               
                 Shoulder Angle 
                 35 degrees 
                 35 degrees 
                 35 degrees 
               
             
          
           
               
                 Rim to Shoulder 
                 1.3 
                 33.02 
                 1.3 
                 33.02 
                 1.3 
                 33.02 
               
               
                 Base to Shoulder 
                 1.1 
                 27.94 
                 1.1 
                 27.94 
                 1.1 
                 27.94 
               
               
                 Overall Case Length 
                 1.66 
                 42.164 
                 1.66 
                 42.164 
                 1.66 
                 42.164 
               
               
                 Headspace Measurement 
                 1.36 
                 34.544 
                 1.36 
                 34.544 
                 1.36 
                 34.544 
               
               
                 Neck Diameter 
                 0.307 
                 7.7978 
                 0.314 
                 7.9756 
                 0.338 
                 8.5852 
               
               
                 Neck Length 
                 0.28 
                 7.112 
                 0.285 
                 7.239 
                 0.302 
                 7.6708 
               
               
                 Rim Thickness 
                 0.05 
                 1.27 
                 0.05 
                 1.27 
                 0.05 
                 1.27 
               
               
                 Extractor Groove Width 
                 0.039 
                 0.9906 
                 0.039 
                 0.9906 
                 0.039 
                 0.9906 
               
               
                 Extractor Groove Diameter 
                 0.350 
                 8.89 
                 0.350 
                 8.89 
                 0.350 
                 8.89 
               
               
                 Body Taper 
                 0.014 
                 0.3556 
                 0.014 
                 0.3556 
                 0.014 
                 0.3556 
               
               
                 Shoulder Base Diameter 
                 0.434 
                 11.0236 
                 0.434 
                 11.0236 
                 0.434 
                 11.0236 
               
               
                 Shoulder length 
                 0.09 
                 2.286 
                 0.085 
                 2.159 
                 0.068 
                 1.7272 
               
               
                   
               
             
          
         
       
     
     Referring now to  FIG. 3 , there is shown an embodiment of the subject system and concept. Ammunition cartridge  10 ′ includes annularly contoured rim section  14 ′ which is circular in cross-sectional contour and is formed symmetrically about axis line  18 ′. Annularly contoured rim section  14 ′ has an outer diameter of 0.422 inches (within manufacturing tolerance ranges) and includes opposing first and second ends  24 ′ and  26 ′. Annular rim section  14 ′ is separated from hollow main body section  28 ′ by extractor groove section  22 ′. It is to be understood that annular rim section  14 ′ and hollow main body section  28 ′ are formed in one-piece formation. Hollow main body section  28 ′ includes charge chamber  46 ′. Annularly contoured rim section  14 ′ having the opposing first and second ends  24 ′ and  26 ′ is adapted to receive a primer, as was provided for the preferred embodiment discussed. 
     The extractor groove  22 ′ is seen to be formed adjacent rim section  14 ′ second end  24 ′ with the extractor groove having an outer diameter less than the outer diameter of the annularly contoured rim section  14 ′. The extractor groove  22 ′ has a diameter of 0.350 inches (within manufacturing tolerance ranges) as opposed to the 0.422 inches of the diameter of the rim  14 ′. 
     The hollow main body section  28 ′ is adapted to receive a powder charge within charge chamber  46 ′ and hollow main body section  28 ′ is symmetrically formed about axis line  18 ′ to provide a cross-sectional circular contour throughout the length of hollow main body section  28 ′. Hollow main body section  28 ′ extends from hollow main body section first end  36 ′ to main body section second end  38 ′ in the direction of axis line  18 ′. The main body section second end  38 ′ is adapted to receive a predetermined caliber size bullet  12 ′ with the hollow main body section  28 ′ contoured to taper toward the axis line  18 ′ from the main body section first end  36 ′ to main body section second end  38 ′. The taper formed by hollow main body section  28 ′ is at an angle of 0.36° with a nominal body tapering of 0.020 inch taper (all within manufacturing tolerance ranges) and provides for a diminishing diameter from 0.448 inches to 0.428 inches in diameter for receipt of a 0.40/10 mm caliber bullet  12 ′. The combined length in axis line direction  18 ′ of main body section  28 ′, in combination with the extractor groove  22 ′ and the rim section  14 ′ is 1.8 inches within manufacturing tolerance ranges and results in an external diameter of main body second section end  38 ′ having a diameter of 0.428 inches (within manufacturing tolerance ranges). 
     Hollow main body  28 ′ is tapered throughout the length of main body  28 ′ at an angle of 0.36° with a nominal body tapering of 0.020 inch taper. Thus, hollow main body section  28 ′ tapers from a diameter of 0.448 inches to 0.428 inches (within manufacturing tolerance ranges). Thus, hollow main body  28 ′ is adapted to receive bullet  12 ′ having a 0.40/10 mm caliber, while simultaneously maintaining the overall length of ammunition cartridge  10 ′ at 1.8 inches (within manufacturing tolerance ranges). In this manner, ammunition cartridge  10 ′ is adapted to be received within a standard AR15 type rifle magazine  48 , as is shown in  FIG. 4 , while simultaneously permitting the insert of a plurality of cartridges  10 ′ in an alternating side-by-side relation with respect to a plurality of cartridges  10 ′ inserted into the rifle magazine  48 . 
     The general dimensions of ammunition cartridge  10 ′ as fabricated are shown in Table 2 for a 0.40/10 mm caliber bullet. 
     
       
         
               
               
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                   
                 Cartridge 
               
             
          
           
               
                   
                   
                 400 in. 
                 mm 
               
               
                   
                   
               
             
          
           
               
                   
                 Bullet Diameter 
                 0.400 
                 10.16 
               
               
                   
                 Rim Diameter 
                 0.422 
                 10.7188 
               
               
                   
                 Base Diameter 
                 0.448 
                 11.3792 
               
               
                   
                 Bullet Receiving End Diameter 
                 0.428 
                 10.8712 
               
               
                   
                 Rim to Base 
                 0.2 
                 5.08 
               
               
                   
                 Base to Bullet Receiving End 
                 1.6 
                 40.64 
               
               
                   
                 Overall Case Length 
                 1.8 
                 45.72 
               
               
                   
                 Headspace Measurement 
                 1.8 
                 45.72 
               
               
                   
                 Rim Thickness 
                 0.050 
                 1.27 
               
               
                   
                 Extractor Groove Width 
                 0.039 
                 0.9906 
               
               
                   
                 Extractor Groove Diameter 
                 0.350 
                 8.89 
               
               
                   
                 Body Taper 
                 0.020 
                 0.508 
               
               
                   
                   
               
             
          
         
       
     
     Table 3 shows the enhanced energy of the new ammunition cartridges compared to the 5.56 NATO/.223 ammunition cartridge demonstrating the expressed purposes of the inventive concepts described herein. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Comparison of the 
               
               
                 enhanced energies in foot pounds of the Prior Art 
               
               
                 .223/5.56 cartridge vs. cartridges of inventive concept 
               
             
          
           
               
                   
                 Cartridge 
               
             
          
           
               
                   
                 .223/5.56 
                 .270 
                 .280 
                 .300 
                 .400 
               
               
                   
                 60 gr 
                 130 gr 
                 140 gr 
                 165 gr 
                 200 gr 
               
               
                   
               
             
          
           
               
                 Muzzle energy 
                 1300 
                 2104 
                 2182 
                 2382 
                 2742 
               
               
                 100 yards 
                 973 
                 1783 
                 1864 
                 2002 
                 2085 
               
               
                 200 yards 
                 715 
                 1503 
                 1551 
                 1672 
                 1557 
               
               
                 300 yards 
                 514 
                 1257 
                 1294 
                 1385 
                 1151 
               
               
                 400 yards 
                 362 
                 1044 
                 1073 
                 1142 
                 844 
               
               
                 500 yards 
                 250 
                 862 
                 885 
                 936 
                 630 
               
               
                   
               
             
          
         
       
     
     Although this invention has been described in connection with specific forms and embodiments thereof, it will be appreciated that various modifications other than those discussed above may be resorted to without departing from the spirit or scope of the invention as defined in the appended claims. For example, functionally equivalent elements may be substituted for those specifically shown and described, certain features may be used independently of other features, and in certain cases, particular locations of elements, steps, or processes may be reversed or interposed, all without departing from the spirit or scope of the invention as defined in the appended claims. It is also to be understood that all dimensions and angles specified in the Specification and Claims are to be understood to be within manufacturing tolerances.