Patent Publication Number: US-2018038673-A1

Title: Ammunition projectile having improved aerodynamic profile and method for manufacturing same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to projectiles intended to be fired from firearms, and more particularly to a projectile that includes a specially contoured leading section that is designed to enhance the aerodynamic properties of the projectile and the method of manufacturing the projectile. 
     2. Description of the Prior Art 
     The prior art discloses many attempts to improve the basic design of projectiles intended for use with firearms. With the interest that exists in the field of sport target shooting and with the interest of outdoorsmen, hunters and the like, substantial attention has been given to enhance the external ballistics of the projectile through the design of bullets that yield greater accuracy and range. In addition to accuracy and range, concern has been paid to increasing the velocity of a projectile or a bullet for a given charge. Increasing the velocity of the projectile as well as reducing the drag of the projectile depends very much on the aerodynamic qualities of the projectile itself. 
     The geometry of a projectile for a firearm is generally divided into symmetrical sections. The body or shank of the projectile is that part of the projectile that comes into full contact with the barrel rifling of the firearm. The cylindrical portion of the projectile is generally referred to as the bearing surface. The prior art generally refers to the term “ogive” to describe the specific point where the leading section of the projectile begins. This is typically where the bearing surface ends and the leading section begins. While the term “ogive” is often used to describe the particular point on the projectile where the leading section reaches the full projectile diameter of the central section of the projectile, the ogive properly refers to the entire curve of the projectile from the distal tip of the projectile to the central section thereof. 
     As disclosed in the prior art, the ogive of a projectile is usually characterized by the length of its radius. The radius is often given in calibers. The ogive profile of the leading section of a projectile for a firearm is generally described as a tangent ogive design or a secant ogive design. The prior art defines a tangent ogive design as one where the intersection of the central section of the projectile and the radius of the ogive blend together at a tangent point. In a secant ogive design, the point of intersection between the central and leading sections of the projectile is not tangent, the ogive radius being a secant of the arc circle of the ogive. 
     Irrespective of whether a projectile is categorized as a tangent or a secant ogive design, the distal tip of the ogive is referred to as a meplat. The shape of the meplat has a great effect on external ballistics. The shape of the meplat can also have an effect on terminal ballistics and performance. A representative sample of prior art discloses a projectile that employs an ogive geometry and a relatively short length of the extreme distal tip of the ogive portion of the projectile is further infolded toward the center line of the projectile by a relatively few degrees thereby defining a tapered tip having a void volume in the most distal portion of the open end of the projectile defining a meplat cavity. This configuration can adversely affects the aerodynamic efficiency of the projectile. As the meplat cavity is enlarged, the aerodynamic efficiency of the projectile deteriorates. 
     The present invention overcomes the disadvantages of the designs disclosed in the prior art by utilizing a leading section of a projectile that comprises ogive segment geometry constituting a secant ogive design adjacent the central section of the projectile and a conical segment extending from the secant ogive segment at the distal end of the projectile. The apex angle of the surface of the conical segment at the distal end of the projectile is within the range of 20°-40° of arc. The use of a leading section comprising a secant ogive design and a conical segment at the distal end will, by definition, require smaller point angles to create a projectile that will be optimized based on the purpose and use of the projectile. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a geometrical configuration for a projectile intended to be used with firearms having a geometrical configuration that improves the aerodynamic efficiency of the projectile and the method for manufacturing the projectile. The projectile comprises a preformed slug or bullet core that can be made of lead but is preferably a lead core in a deformable copper jacket. The projectile comprises a substantially cylindrical central section having an outer bearing surface is adapted to come into full contact of the barrel rifling of the firearm. The cylindrical central section extends forwardly into a leading section that is coaxial with the central section. The leading section comprises a secant ogive segment that intersects with the bearing surface of the central section at an ogive radius that is a secant of the arc circle of the ogive. The secant ogive segment extends into a conical segment at the distal end of the leading section. The surface of the conical segment of the leading section is projected into an apex that is uniformly disposed about the common axis of the central and leading sections of the projectile. The apex angle of the surface of the conical segment is within the range of 20°-40° of arc. The conical segment is approximately 20% of the axial length of the leading section at the distal end of the projectile. The diameter of the meplat at the distal tip of the conical segment of the projectile is uniformly disposed about the common axis of the leading and central sections of the projectile and the area thereof is substantially less than the meplat area of a projectile employing a tangent ogive design for the leading section. 
     It is an object of the present invention to provide a projectile for a firearm having enhanced external ballistics. 
     It is another an object of the present invention to provide a projectile for a firearm having improved aerodynamic stability. 
     It is still another object of the present invention to provide an improved projectile for a firearm that employs a secant ogive design that reduces aerodynamic drag. 
     It is still yet another object of the present invention to provide a projectile for a firearm that has a meplat of reduced area to enhance aerodynamic properties. 
     It is still yet another object of the present invention to provide an improved design for a projectile intended for use in a firearm that is inexpensive and easy to fabricate. 
     The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objectives and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  illustrates a side view of an enlarged scale projectile for firearms in accordance with the present invention. 
         FIG. 2 a    is a schematic view of a prior art projectile having a tangent ogive design adjacent the central, cylindrical section of the projectile. 
         FIG. 2 b    is a schematic view of a prior art projectile having a secant ogive design adjacent the central, cylindrical section of the projectile. 
         FIG. 3  is an exploded, perspective elevation view of a die assembly used to manufacture projectiles in accordance with the present invention. 
         FIG. 4  is a cross-sectional view of the die piece shown in  FIG. 3  used to manufacture projectiles in accordance with the present invention. 
         FIG. 5  is an end view of the die piece shown in  FIG. 1  illustrating the conical surface to be impressed on the distal end of a projectile in accordance with the present invention. 
         FIG. 6  is a partial cross-sectional view of the present invention projectile forming die showing the structural elements thereof in their assembled relation. 
     
    
    
     DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT. 
     The present invention design for the improvement of a projectile for a firearm can be best understood by initial reference to  FIGS. 2 a  and 2 b    which illustrate prior art projectile designs employing a tangent ogive design and a secant ogive design, respectively. The design of a bullet or projectile for firearms must solve two basic problems. Firstly, while the projectile is in the barrel of a firearm, it must form a seal with the firearm&#39;s bore. The projectile must also engage the barrel rifling without damaging or excessively fouling the firearms bore, and, without distorting the projectile which could reduce accuracy. The interactions between the projectile and the bore of the firearm is generally referred to as “internal ballistics.” The present invention relates to the principles affecting the projectile once it leaves the barrel of the firearm, this being generally referred to as “external ballistics.” The geometry of a bullet or projectile can be broken down into symmetrical sections. The body or central section of a projectile is that part of a projectile that comes into full contact with the barrel rifling. 
     The term “ogive” is commonly used to describe the specific point where the curving part of the leading section of the projectile begins. The terms “ogive” or “ogive profile” are used to describe the entire leading curve section of a projectile.  FIG. 2 a    illustrates a prior art design of a projectile employing what is referred to as a “tangent radius ogive.” In a tangent ogive design, the interface  30  between central section  31  and leading section  30  is at the tangent of the tangent radius  34 , the curved profile for leading section  33 .  FIG. 2 b    illustrates a prior art design employing a secant ogive design. In a secant ogive design, the intersection  35  between the ogive or leading section  37  and central section  36  does not flow together smoothly. The point of intersection  35  is not tangent, the ogive radius being a secant of the arc circle of the ogive. The difference between a tangent ogive design and a secant ogive design is that the latter provides a longer, tapered curvature to leading section  37 . The design of the present invention improves the external ballistics of the projectile by modifying the geometry of the leading section of the projectile. 
     Referring to  FIG. 1 , a projectile  40  in accordance with the present invention comprises leading section  41 , central section  42  and boat tail  43 , all axially aligned along longitudinal center line  44 . Central section  42  is uniformly cylindrical and is adapted to come into full contact with the barrel rifling. Leading section  41  axially extends forwardly from central section  42 . The interface  45  between leading section  41  and central section  42  is a secant ogive design that displays the tapered extended profile as described with respect to  FIG. 2 b   . The boat tail or trailing section  43  axially extends from central section  42  opposed to leading section  41 . 
     Contrary to the designs taught by the prior art, a conic segment  46  extends forwardly from base segment  47  of leading section  41 . The surface  48  of conic segment  46  projects to apex  49  on longitudinal center line  44 . The conic segment  46  is truncated at the distal tip of the ogive to form a meplat  50  that is inwardly folded along the center line to form a conventional meplat cavity (not shown). The apex angle  51  of conic surface  48  is in the range of 20°-40° of arc. To optimize the aerodynamic properties of projectile  40 , the axial length of conical segment  46  is approximately 20% of the total axial length of leading section  41 . 
     An understanding of the projectile forming die employed to manufacture the present invention projectile  40  can be best seen by reference to  FIGS. 3-6 , inclusive, the die assembly generally being designated by reference numeral  60 . Die assembly  60  employs a cylindrical die block  61  having external threads  62  with which locking ring  63  is engaged in order to mount and stabilize die block  61  to a conventional reloading tool (not shown). A lower central bore  64  is axially formed in the lower portion of the die block  61  for receiving projectile seating element  65 . Projectile seating element  65  has a cylindrical outer body  66  adapted to slidably engage with lower central bore  64 . The lower portion of projectile seating element  65  extends axially downwardly into an engagement rim  67  which is coupled to conventional reloading tools. After engagement rim  67  is secured to the reloading tool, lock ring  63  is rotated downwardly against the reloading tool to maintain stability between the reloading tool and die block  61 . A projectile seating bore  68  is axially disposed in the upper portion of projectile seating element  65  for receiving and supporting projectile  40 . To provide consistent engagement of seating element  65  within die block  61  during the manufacturing process, the upper end  70  of projectile seating element  65  adjacent seating bore  68  is tapered inwardly and is adapted to be positioned adjacent beveled surface  71  contiguous with central bore  64  of die block  61 . An upper threaded central bore  75  is axially disposed into die block  61  in opposition to lower central bore  64  and is adapted to receive threaded shaft  76  of die cap  77 . When die cap  77  is engaged within upper threaded central bore  75 , die cap  77  will be in axial alignment with projectile seating bore  68 . 
     The conic segment  46  of leading section  41  of the present invention projectile is formed with die piece  80 . As can be seen best in  FIG. 4  and  FIG. 5 , die piece  80  is a cylindrical member having a base  81  perpendicular to the axis  82  of the die piece, a conical depression  83  being disposed into base  81  of die piece  80  consistent with the specifications of conic section  46  of leading section  41  of projectile  40 . The upper end of die piece  80  extends into a tapered conical positioning surface  84 , the apex  85  of conical positioning surface  84  being axially aligned with the apex  86  of conical depression  83 . A cylindrical bore  89  is axially disposed into threaded shaft  76  adapted to slidably receive die piece  80 . The upper end of cylindrical bore  89  is formed into a conical receiving surface  90  that is adapted to engage conical positioning surface  84  of die piece  80  to maintain die piece  80  in axial alignment with the projectile seating base  68  during use. 
     The method by which the present invention projectile can be formed can best understood by reference to  FIGS. 3 and 6 . The first step is to mount engagement rim  67  of projectile seating element  65  to a conventional reloading tool (not shown). Die block  61  is mounted upon projectile seating element  65  slidably engaging lower central  64  of die block  61  with outer surface  66  of projectile seating element  65 . Once in place, lock ring  63  secures the coupling between die block  61  and the reloading tool. A preformed slug or bullet core that is to be formed into the present invention projectile  40  is positioned within projectile seating bore  68  of projectile seating element  65 . As can be best seen in  FIG. 6 , boat tail  43  of projectile  40  is disposed against the bottom surface of projectile seating base  68 . After engaging die piece  80  within cylindrical bore  89  of threaded shaft  76 , threaded shaft  76  is rotatably engaged to upper threaded central bore  75  of die block  61 . Die cap  77  and the integral threaded shaft  76  are rotatably lowered until the leading section  41  of projectile  40  is engaged with conical depression  83  of die piece  80 . The die cap  77  and integral threaded shaft  76  are rotatably lowered into die block  61  causing the surface of the conical depression  83  of the piece  80  to impose compressive force against conical surface  48  until the axial length of conical segment  46  is approximately 20% of the total axial length of leading section  41  of projectile  40  and conic segment  46  and meplat  50  define an apex angle  51  that is within the range of 20°-40° of arc.