Patent Publication Number: US-2016223303-A1

Title: Cartridge for a firearm

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/104,118, filed 16 Jan. 2015. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to ammunition for firearms and a reamer for forming a firing chamber in the firearm to receive the ammunition. 
     BACKGROUND OF THE INVENTION 
     In the firearm and ammunition industry, the cartridge for a firearm is essential in determining the speed and power of the bullet once the firearm is fired. Clearly, bullet speed and power can be affected by changing the size of the cartridge and the amount of propellant, such as gun powder, carried by the cartridge. However, it is equally clear that increases in the size of the cartridge and the amount of powder have an upper limit. Also, as the size of the cartridge and amount of powder increases the size of the firearm in which the cartridge is used must increase resulting in a less versatile instrument. 
     It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art. 
     Accordingly, it is an object of the present invention to provide a new and improved cartridge for a firearm. 
     It is another object of the present invention to provide a new and improved cartridge for a firearm that maximizes case useable capacity. 
     Another object of the invention is to provide a new and improved cartridge for a firearm that maximizes bullet speed, resulting in more down range energy and distance, without substantially increasing the size of the case or cartridge. 
     Another object of the invention is to provide a new and improved cartridge for a firearm that improves projectile or bullet accuracy for longer ranges. 
     SUMMARY OF THE INVENTION 
     Briefly, the desired objects of the instant invention are achieved in accordance with a long-range precision firearm cartridge case designed to maximize cartridge case useable capacity. The case is a hollow cylinder including a head end and a projectile receiving end, the cylinder includes a generally cylindrical body portion extending from the head end to a frusto-conical shoulder. The body portion has a central aperture extending into the head end for receipt of a primer and a cartridge extraction groove formed around the periphery of the body portion adjacent the head end. The frusto-conical shoulder is integrally formed with the body portion and a tapered shoulder portion tapers from the body portion to a generally cylindrical integrally formed neck portion. The neck portion extends longitudinally from the shoulder portion and has a diameter smaller than the diameter of the body portion and terminates in an open mouth at the projectile receiving end. The neck portion and the tapered portion extend longitudinally a distance such that a bullet positioned in the cartridge case extends through the neck portion and the tapered portion a distance no greater than to a plane through the frusto-conical shoulder, whereby cartridge case useable capacity is maximized. The desired objects of the instant invention are further realized in accordance with a long-range precision firearm cartridge including a cartridge case and a projectile. The cartridge case including a hollow cylinder with a head end and a projectile receiving end. The cylinder includes a generally cylindrical body portion extending from the head end to a frusto-conical shoulder, the body portion having a central aperture extending into the head end for receipt of a primer and a cartridge extraction groove formed around the periphery of the body portion adjacent the head end. The frusto-conical shoulder is integrally formed with the body portion and a tapered shoulder portion tapering from the body portion to a generally cylindrical integrally formed neck portion. The neck portion extends longitudinally from the shoulder portion and has a diameter smaller than the diameter of the body portion and terminates in an open mouth at the projectile receiving end. A primer fitted into the central aperture extending into the head end in communication with a flash-hole. Combustible propellant in the body portion. A projectile fitted into the projectile receiving end and the neck portion and the tapered portion extending longitudinally a distance such that the projectile positioned in the cartridge case extends through the neck portion and the tapered portion a distance no greater than to a plane through the frusto-conical shoulder, whereby cartridge case useable capacity is maximized; 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings, in which: 
         FIG. 1  is a plan view of a prior art cartridge for use in an AR-15; 
         FIG. 2  is a plan view of a cartridge in accordance with the present invention, illustrating dimensions in an unfired and a fired configuration; 
         FIG. 3  is a chart illustrating the differences between the cartridge of  FIG. 1  and the cartridge of  FIG. 2 ; 
         FIG. 4  is a plan view of a cartridge illustrating the “bullet jump” of a cartridge; 
         FIG. 5  is a schematic illustration of a bore rider reamer for use in preparation of an AR-15 chamber to use the cartridge of  FIG. 2 ; and 
         FIG. 6  is a schematic illustration of a finish reamer for use in preparation of an AR-15 chamber to use the cartridge of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Turning now to the drawings, attention is first directed to  FIG. 1  which illustrates a prior art cartridge, generally designated  10 , that is specifically designed for use in an AR-15 rifle. Cartridge  10  is known as a 223 Remington cartridge in the civilian field and as a 5.56 NATO cartridge in the military. Cartridge  10  includes a case  12  and a projectile or bullet  14 . Bullet  14 , in this illustration, is an 80 gr Sierra HP Boattail Matchking. 
     Referring to  FIG. 2 , a cartridge  20  in accordance with the present invention is illustrated. Cartridge  20  includes a case  22  and a projectile or bullet  24 . Case  22  is generally a hollow cylinder having a restricted neck  26  and preferably formed of brass. Case  22  includes a head end  30  and a mouth end  32 . Head end  30  includes a central aperture  34  for receipt of a primer (not shown). A generally cylindrical body portion  36  extends from head end  30  to a frusto-conical shoulder  38 . Central aperture  34  is in communication with an interior volume  40  defined primarily by case body portion  36 . A cartridge extraction groove  42  is formed around the periphery of body portion  36  proximate head end  30 . Shoulder  38  is tapered (tapered portion designated  39 ) from body portion  36  to generally cylindrical neck portion  26 . Neck portion  26  has a diameter smaller than the diameter of body portion  36  and terminates in an open mouth  44  at mouth end  32 . 
     Bullet  24  is carried by neck portion  26 , filling neck portion  26 , with a portion of bullet  24  extending through tapered portion  39  of body portion  22  approximately to a plane through shoulder  38 . In the embodiment illustrated, bullet  24  is a Boattail type approximately 80 grains. It will be understood however that a large variety of different bullets may be used, such as 55 gr to 70 gr. The difference in position between bullet  14  and case  12  of  FIG. 1  and bullet  24  and case  22  of  FIG. 2 , as well as the difference in throats and bullet jump, can be seen in the figures. This difference in bullet position results in more useable capacity in case  22  (see chart and description below). 
       FIG. 4 , specifically illustrates a plan view of a cartridge “bullet jump”. Generally, the definition of “bullet jump” is the unrestricted clearance between the ogive of the bullet where the actual .224 cal. (in the present examples) begins, designated  45 , on the shank of the bullet to the bore where the bullet engages the actual rifling, designated  46 . 
     Case  22  has nominal dimensions intended to establish a standard cartridge type. Variations from the nominal dimensions are tolerated by minimal deviations. The dimensions of cartridge  20  are described using both pre-fired and fired dimensions in conjunction with a schematic ( FIG. 2 ), the schematic of a chamber bore rider reamer  FIG. 5  and finish reamer  FIG. 6 , designated  50  and  52 , respectively. All dimensions illustrated and described are in inches. 
     Referring specifically to  FIG. 3 , a chart is illustrated listing major measurements in both the prior art cartridge (223 REM or 5.56 NATO) and showing the major differences. As can be seen from the chart, the length of the case for the 223 REM or 5.56 NATO cartridge is 0.114 inches longer than the case of the present invention but the capacity of the 223 REM or 5.56 NATO cartridge is 0.82 grains less and the useable case capacity is 7.01 grains less. This difference results in the bullet or projectile being driven at 200 fps (feet per second) faster for any barrel length, thus producing more down range energy and distance. Plus, an added advantage is that it will also work well in a bolt action gun as to fit in with lighter bullets, such as 42 gr, 45 gr, 55 gr, 62 gr, to 77 gr varmint cartridges or it can be built into a lightweight youth rifle. In all cases the length will not exceed 2.260 in in the AR 15 or gas operated system. The present improved cartridge basically gives AR 10 in 7.62 capability in an AR 15 platform of 5.56 mm. 
     Turning to  FIG. 5 , a bore rider reamer  50  is illustrated that is specifically designed to ream or form a firearm chamber into a chamber compatible with cartridge  20  and  FIG. 6  illustrates a finish reamer  52 . To this end, it will be noted that the chamber has dimensions slightly larger than an unfired cartridge  20 . When cartridge  20  is fired in the chamber formed with reamers  50  and  52  the fired dimensions set forth above ( FIG. 2 ) are achieved. The unfired to fired dimensions, along with the original form, are specifically calculated to maximize powder combustion and direction of the propellant gasses. 
     Thus, a new and improved cartridge for a firearm is disclosed that maximizes case useable capacity. By carefully designing the diameters of the cartridge and position of the bullet in the case, the maximum efficiency of the cartridge can be achieved. The new and improved cartridge maximizes bullet speed, resulting in more down range energy and distance, without substantially increasing the size of the case or cartridge. Further, the new and improved cartridge improves projectile or bullet accuracy for longer ranges. 
     Various changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof, which is assessed only by a fair interpretation of the following claims. 
     Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is: