Abstract:
A crimped-case cartridge comprising a bullet and a casing wherein the casing has alternating crimped and uncrimped sections at its terminal end. The crimped sections form increased contact sections with the bullet, with the uncrimped sections maintaining proper head space for the cartridge. The amount of crimped section versus the amount of uncrimped section is variable to meet a variety of desired ballistic characteristics. Likewise, the amount of taper, angle of crimp, depth of crimp, and pressure applied in the crimped section is also variable. The crimped-case cartridge is employable with bullets having cannelure depressions of any geometry or no cannelure at all. Additionally, a bullet having a cannelure geometry mated to the crimped section geometry is disclosed. Likewise, a plurality of taper-crimp dies forming the crimped-die cartridge is disclosed.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to cartridges having crimped casings.  
         BACKGROUND OF THE INVENTION  
         [0002]    Reliable cartridge manufacture requires uniformity from one cartridge to the next in order to obtain consistent ballistic performance. Among other considerations, proper bullet seating and bullet-to-casing fit is required. In this manner, a desired pressure develops within the casing during firing prior to bullet and casing separation. Historically, bullets employ a cannelure, which is a slight annular depression formed in a surface of the bullet at a location determined to be the optimal seating depth for the bullet. In this manner, a visual inspection of a cartridge could determine whether or not the bullet is seated at the proper depth. Once the bullet is inserted into the casing to the proper depth, one of two standard procedures is incorporated to lock the bullet in its proper location. One method is the crimping of the entire end of the casing into the cannelure. A second method does not crimp the casing end; rather the bullet is pressure fitted into the casing. However, these methods are problematic.  
           [0003]    Crimping the end of the casing into the bullet&#39;s cannelure creates several problems. Most significantly, it changes the head spacing of the bullet, or more correctly, does not create a consistent or accurate head space from one cartridge to the next. Proper head space is critical in semi-automatic and automatic firearms. Any cartridge that does not have a consistent head space cannot be fired from semi-automatic and automatic weapons. The market for the manufacture of current crimped case cartridges is therefore limited to firearms where head space is not critical, for example, revolvers. Consequently, current crimped cartridge technology severely limits the market in which the product can be sold, thereby limiting profit potential.  
           [0004]    Yet another problem with current crimped case technology is safety. If a cartridge having improper head spacing is chambered into a semi-automatic or automatic weapon, an extremely dangerous situation can occur. More specifically, the case can feed too far into the chamber and partially into the barrel of the firearm. Upon discharge of the weapon, the rapid pressure increase inside the casing causes a slight deformation of the casing around the bullet. If the case has fed into the end of the barrel, the case has no space to expand. Consequently, the casing will often fail, causing the rear of the casing to blow out, severely damaging the firearm, the operator, or both.  
           [0005]    In contrast to current case crimping methods, bullets are often pressure-fit into the casing. This process allows the cartridge to maintain proper head spacing, but a number of other problems are created. Pressure fitting yields a lower bullet-to-casing contact pressure, resulting in a looser fit between the elements. The looser fit makes the bullets subject to re-seating in the case, which unpredictably alters the ballistic characteristics of the cartridge. For example, bullets in a magazine of a firearm tend to re-seat due to recoil associated with firing other rounds if there is insufficient casing to bullet contact pressure. The unpredictability of the performance of re-seated bullets affects the overall accuracy of a firearm. This creates an extremely serious problem when accuracy is required, as in military and law enforcement applications.  
           [0006]    Yet another problem with pressure fitted bullets that ultimately effects accuracy is inefficient powder burn. Inefficient powder burn is known as flashing, which generally results in unburned powder exiting the barrel behind the bullet. This creates two problems. First, the inefficient powder burn lowers the initial pressure generated by the oxidation of the charge, resulting in a lower pressure within the cartridge upon ignition. Consequently, inconsistent ballistic characteristics are attained, yielding an inaccurate firearm. Further, unburned powder oxidizing outside of the firearm is a health hazard that may cause excessive eye damage due to bright powder “flashes” outside of the firearm.  
           [0007]    An early attempt to provide adequate bullet-to-casing contact pressure tried crimping the sides of the casing in the section where the bullet seated. For example, a British stab crimp was fairly common in the late 19 th  century as a means of maintaining proper head spacing and at the same time substantially increasing the contact strength between the bullet and the casing. An example of a British stab crimp is depicted in FIG. 1. The stab crimping had a tendency to deform or shave mass unevenly from the bullet as it exited the casing, thereby affecting the bullet&#39;s ballistic characteristics as it traveled to the target, once again yielding an inaccurate round.  
           [0008]    Other attempts have been made to maintain proper head spacing by not crimping the end of the cartridge, while at the same time preventing any re-seating of the bullet as a result of recoil. For example, a casing crimp beneath the bottom seat of the bullet has been employed, and is depicted in FIG. 2. This casing crimp prevents, to a limited extent, bullet re-seating. However, the casing crimp does nothing to increase the integrity of the contact between the bullet and the casing. Therefore, the problem of flashing still commonly occurs.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention comprises a crimped case cartridge having a bullet and a casing, wherein the end of the casing is alternately crimped and uncrimped around the bullet. The crimped sections serve to create increased contact pressure between the casing and the bullet, while the uncrimped sections maintain a proper head space for the cartridge. Additionally, the bullet includes a cannelure mating with the crimped section. The cannelure is designed to prevent any re-seating of the bullet while providing a smooth case release surface. Further, the cartridge is manufactured with any of a variety of taper-crimp dies used in manufacturing crimped-case cartridges.  
           [0010]    In accordance with further aspects of the invention, at least two uncrimped sections are formed in the casing.  
           [0011]    In accordance with other aspects of the invention, the ratio of crimped section to uncrimped section is variable based upon desired ballistic performance.  
           [0012]    In accordance with still further aspects of the invention, the depth of the crimped section is variable based upon desired ballistic performance.  
           [0013]    In accordance with yet other aspects of the invention, the angle of the crimped section is variable based upon desired ballistic performance.  
           [0014]    In accordance with still further aspects of the invention, the contact pressure between the crimped section and the bullet is variable based upon desired ballistic performance.  
           [0015]    In accordance with yet another aspect of the invention, the crimped casing can be employed with bullets having any cannelure geometry.  
           [0016]    In accordance with further aspects of the invention, the crimped casing can be employed with bullets without a cannelure.  
           [0017]    As will be readily appreciated from the foregoing summary, the invention provides a crimped case cartridge that maintains proper head space while simultaneously controlling the bullet-to-casing contact pressure. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0019]    [0019]FIG. 1 is a side view of an aspect of a prior art cartridge;  
         [0020]    [0020]FIG. 2 is a side view of another aspect of a prior art cartridge;  
         [0021]    [0021]FIG. 3 is an exploded side view of a crimped casing and bullet;  
         [0022]    [0022]FIG. 4 is a sectional view of the crimped casing of FIG. 3 taken along the line  4 - 4 ;  
         [0023]    [0023]FIG. 5 is a sectional side view of a taper-crimp die;  
         [0024]    [0024]FIG. 6 is a sectional view of the taper-crimp die of FIG. 5, taken along the line  6 - 6 ; and,  
         [0025]    [0025]FIG. 7 is a sectional side view of another aspect of the taper-crimp die. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    [0026]FIG. 1 depicts an example of a prior art cartridge. The cartridge  30   a  consists of a bullet  32   a  and a casing  34   a . The bullet  32   a  is seated and pressure-fitted within the casing  34   a  to bullet depth  38 . Additionally, stab crimps  36  are formed in the casing in the area defined by the end of the casing and the bullet depth  38   a . The stab crimps are inwardly directed deformations in the casing that increase the contact pressure between the casing and the bullet. Consequently, the bullet  32   a  is firmly connected to the casing  34   a  until sufficient pressure is created within the casing  34   a  upon ignition of a charge contained within the casing.  
         [0027]    [0027]FIG. 2 depicts another example of a prior art cartridge. The cartridge  30   b  consists of a bullet  32   b  inserted into a casing  34   b  to a bullet depth  38   b . A cannelure crimp  40  is formed annularly around the casing  34   b  in an area below the bullet depth  38   b . This cannelure crimp  40  serves to prevent the bullet from seating itself to a greater depth in the casing  34   b.    
         [0028]    [0028]FIG. 3 depicts an exploded view of a crimped case cartridge  44  in accordance with the present invention. The crimped case cartridge  44  consists of a bullet  32   c  and a casing  34   c . The bullet  32   c  includes a seating edge  48  and a tapered relief surface  50  that together form a cannelure  46 . As discussed in more detail below, the casing  34   c  is crimped to the bullet  32   c  along a crimped portion  52 . The seating edge  48  prevents re-seating of the bullet  32   c  in the casing  34   c . Furthermore, the tapered relief surface  50  provides an even expansion of the crimped portion  52  and smooth release of the bullet  32   c  from the casing  34   c.    
         [0029]    In the preferred embodiment, the bullet  32   c  includes a cannelure section  46  having a seating edge  48  and a tapered relief surface  50  extending annularly around the bullet that are mated to the angle and depth of the crimp. However, other bullet designs are considered within the scope of this invention. For example, the crimped cartridge of this invention works equally well with bullets having cannelures of other geometries or bullets with no cannelure (not shown). Also, the crimped case cartridge is employable with any currently manufactured bullet design. For example, hollow point, solid point, ball, wad cutter, semi-wad cutter, hydra-shock, cor-lock, ballistic tip, silver tip, partition, boat tail, Teflon coated and others are all various bullet designs compatible with the crimped case cartridge  44 . In addition, the bullet, including any area within the cannelure depression, can be covered with a lubricant (not shown) to reduce any unwanted friction.  
         [0030]    The casing  34   c  has on a terminal edge alternating crimped sections  52  and uncrimped sections  54 . The crimped section  52  is designed to attach the crimped casing  34   c  to the bullet  32   c  in order to increase the bullet rigidity within the casing. The amount of pressure applied to the bullet from the crimped section  52  is variable and dependant upon bullet choice, desired ballistics characteristics, operational requirements, loading standards and the like. For example, a higher bullet-to-case contact pressure can be used to increase the separation force required to propel the projectile, achieving a higher case pressure yielding a higher initial bullet velocity. Conversely, sub-sonic ammunition will likely function with a lower bullet-to-case pressure. Further, the depth and angle of the crimp are also variables that can be manipulated to achieve varying bullet performance requirements or physical characteristics. In the preferred embodiment, a crimp angle of 60 degrees is desirable. However, any other crimp angle is within the scope of this invention. For example, relatively short case length rounds, such as 0.45 or 9 mm, a shallower depth, sharper angled crimp can be used. Conversely, for relatively longer rounds a deeper, more obtuse angle can be employed.  
         [0031]    The uncrimped section  54   b  serves to maintain the proper headspace for the cartridge. The uncrimped section  54   b  retains the cartridge length, thus preventing excessive cartridge feed into a firearm&#39;s chamber or barrel. Maintaining proper headspace is critical to prevent, among other things, excessive pressure buildup resulting in dynamic case failure. Thus, by maintaining at least two evenly spaced, uncrimped sections, the cartridge maintains proper case length, and thus maintains the proper headspace. Consequently, the crimped case cartridge  44  is employable in all firearms, including, revolvers, automatic, semi-automatic, pump action, lever action, bolt action, break action, and breach loading firearms. At least two uncrimped sections are preferred to ensure a cartridge that is well aligned. Nonetheless, it may be possible to construct a cartridge with one uncrimped section.  
         [0032]    [0032]FIG. 4 depicts a top view of the crimped casing  34   c . The casing  34   c  comprises alternating crimped section  52   c  and uncrimped section  54   c  around the entire periphery of the end of the casing. As with the depth and angle of the casing discussed above, the ratio of crimped section  52   c  to uncrimped section  54   c  is variable, with the caveat that at least two uncrimped sections are present in the preferred embodiment and evenly spaced from one another. For example, if a higher contact pressure between the casing and the bullet is desired, a larger crimped section is employed or a greater crimp pressure is applied. Conversely, if a more balanced centering of the cartridge in the chamber is desired, a greater number of uncrimped section  54   c  can be evenly spaced around the casing&#39;s perimeter.  
         [0033]    [0033]FIG. 5 depicts a side sectional view of a taper-crimp die  60  used in the manufacture of a crimped case cartridge  44 . The taper-crimp die encompasses a die housing  62  providing a structure for creating a cartridge. More specifically, the die  60  forms the case  34   c  to the bullet  32   c . The die housing  62  includes threads  72  for attaching the die to a press (not shown) and a grip area  76  for hand manipulation of the die  60 .  
         [0034]    A casing taper  64  is axially located within the die  60  and is shaped to receive a cartridge from cartridge access point  70 . The bore of the casing taper  64  corresponds to an industry standard minimum chamber specifications for the given cartridge being produced. The casing taper  64  can be slightly larger at the cartridge access point  70  in order to receive cartridges with slightly belled cases, although this is not required.  
         [0035]    The casing taper  64  is mated to a crimp taper  66  opposite the cartridge access point  70 . The crimp taper  66  section has a smaller diameter than the case taper  64 . The diameter of the crimp taper decreases as depth into the die  60  increases. As stated above, the depth and angle of the crimp taper  66  is variable dependent upon desired ballistic characteristics or other considerations. Attached to an end of the crimp taper  66  opposite the case taper  64  is an axial bore  72 . The axial bore  72  provides as open area to receive the bullet portion of the cartridge.  
         [0036]    A plurality of relief areas  68   a  are formed in the case taper  64  and the crimp taper  66  sections. The relief areas  68   a  are milled-out sections, generally of semi-circular design, increase the diameter of the respective section in the location of the relief area  68   a . The cartridge  44  is not subjected to a compressive force resulting from manufacture in the relief area  68   a . Consequently, the area of the casing  34   c  corresponding to a respective relief area  68   a  does not deform as a result of the tapering process. Thus, uncrimped sections  54  are formed in the casing section that correspond to the location of the relief areas  68   a    
         [0037]    As the cartridge  44  enters the taper-crimp die  60  through cartridge access point  70 , a first casing taper  64  is encountered. The casing taper section  64  prevents any case bulging during a subsequent crimp taper  66  stage. Following the casing taper  64 , the cartridge enters the crimp taper section  66 . The crimping taper section  66  forms the crimped section  52   c  (see FIG. 4) at the end of the casing  34   c  (see FIG. 4).  
         [0038]    The taper-crimp die  60   a  is employable with all current manual and automated loading and re-loading processes and equipment. The taper-crimp die  60   a  is manufactured to industry standard specifications. More specifically, the taper-crimp die simply replaces standard taper dies currently used in cartridge manufacturing. Consequently, the crimped case cartridge  44  is achieved without adding additional manufacturing steps or significant retooling.  
         [0039]    [0039]FIG. 6 depicts a sectional top view of FIG. 5 taken along and in the direction of section line  6 - 6 . Die housing  62   b  encompasses casing taper section  64  and crimping taper section  66 . At least one relieved section  68   a  is formed in the surface of the crimping taper section  66  and casing taper section  64 . Further, the axial bore  72  extends through the center of the die  60   a.    
         [0040]    The axial bore  72  allows for bullets of the same caliber, but having different lengths extending above the casing to be produced from the same die  60   a . This is especially important when the bullet depth  38  is varied to attain different ballistic characteristics. For example, bullets without cannelures seated to different depths in the casing  34   c  to achieve various initial pressures within the casing  34   c  during ignition.  
         [0041]    The depth of the relief section  68   a  in the casing taper section  64  is variable and serves no function in regards to preventing case  34   c  deformation in this section  64 . The purpose of the relief section  68   a  is to create the uncrimped sections  54  (FIG. 3) in the case  34   c . The crimped and uncrimped sections,  52  and  54  respectively, are formed in the crimp taper section  66 . Thus, the relief sections  68   a  are not necessary in the casing taper section  64 , and thus may not exist in the taper casing section  64 . However, at times lubricants are used in the manufacture of cartridges  44  and excessive lubrication can attach itself to the case  34   c . The relief section  68   a  provides an avenue for any excessive lubrication to pass during the cartridge  44  formation process.  
         [0042]    [0042]FIG. 7 depicts an additional aspect of the taper crimp die  60   b . The physical characteristics are similar to the die depicted in FIGS. 5 and 6. However, unlike the die of FIGS. 5 and 6, the relieved sections  68   b  are not formed within the casing taper section  64 . Rather, the relieved sections  68   b  are formed in an upper end of the die housing and extend down into the crimp-taper section  66   b.    
         [0043]    Removing the relieved sections  68   b  from the casing taper section  64  is an alternative design choice to the die  60   a  depicted in FIG. 5. This design provides a smoother surface in the initial section of the die  60   a . The smoother surface allows for an easier feed of the cartridge  44  into the die  60   a . Likewise, the casing  34   c  receives a more evenly distributed pressure from the casing taper section  64 . Consequently, a consistent casing tolerance is maintained.  
         [0044]    While the preferred embodiment of the invention has been illustrated and described, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the scope of the invention should be determined entirely by reference to the claims that follow.