Abstract:
A projectile has a body with three fins which partially define a meplat. Three flutes are alternatingly arranged with the three fins about an axis of the body. Each of the three flutes is at least partially defined by a curved surface having a substantially smooth radius of curvature that is substantially constant from the meplat to a side surface of the body.

Description:
INTRODUCTION 
       [0001]    Armor-piercing projectiles are typically used in military applications to penetrate metals, drywall, body armor, and other barriers. Typically, such projectiles include a flat meplat and a number of flutes that extend along the body of the projectile. By removing material from the bullet so as to form the flutes, the surface area of the meplat is reduced so as to enable penetration through barriers. 
       SUMMARY 
       [0002]    In one aspect, the technology relates to a projectile having: a body having three fins, wherein the three fins at least partially define: a meplat; and three flutes alternatingly arranged with the three fins about an axis of the body, wherein each of the three flutes is at least partially defined by a curved surface having a substantially smooth radius of curvature that is substantially constant from the meplat to a side surface of the body. In an embodiment, the meplat has a meplat surface substantially orthogonal to the axis. In another embodiment, the meplat has a meplat portion extending substantially along the axis and away from the meplat surface. In yet another embodiment, each of the three flutes is at least partially defined by two curved surfaces, wherein the two curved surfaces intersect at an intersection curve defined by the radius of curvature. In still another embodiment, the body has a maximum outside diameter and the meplat has a meplat diameter about 50% of the maximum outside diameter. 
         [0003]    In another embodiment of the above aspect, each of the three flutes each define a flute length between about 50% to about 55% of the body length. In an embodiment each of the three flutes each define a flute length between about 52% of the body length. In another embodiment, each flute has an included angle of about 120°. 
         [0004]    In another aspect, the technology relates to a projectile having: a meplat surface; a base surface; and a body having an outer surface, the body extending along an axis from the meplat surface to the base surface, wherein the body has a plurality of fins, wherein each of the plurality of fins is defined by: the meplat surface; the outer surface; and a pair of curved surfaces, wherein adjacent curved surfaces of adjacent fins intersect at an intersection curve disposed radially equidistant from the adjacent fins. In an embodiment, adjacent curved surfaces of adjacent fins define a substantially symmetrical flute. In another embodiment, the body defines two flutes, wherein each flute has an included angle of about 150°. In yet another embodiment, the body defines three flutes, wherein each flute has an included angle of about 120°. In still another embodiment, the body defines four flutes, wherein each flute has an included angle of about 90°. 
         [0005]    In another embodiment of the above aspect, the body has a maximum outer diameter of about 0.50″ and at least one curved surface has a radius of about 0.3125″. In an embodiment, the body has a maximum outer diameter of about 0.50″ and at least one flute has a flute volume of about 0.216 cc. 
         [0006]    In another aspect, the technology relates to a projectile having: a body having: an axis; a meplat substantially orthogonal to the axis; a plurality of substantially symmetrical fins defining and separated by a plurality of substantially symmetrical flutes, wherein each flute is formed by two curved surfaces of the body that intersect at an intersection curve. In an embodiment, at a leading point, the two curved surfaces have substantially similar radii of curvature. In another embodiment, each of the plurality of substantially symmetrical flutes is symmetrical about the intersection curve. In yet another embodiment, the plurality of substantially symmetrical flutes has three substantially symmetrical flutes. In still another embodiment, each of the plurality of symmetrical fins has a chisel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    There are shown in the drawings, embodiments which are presently preferred, it being understood, however, that the technology is not limited to the precise arrangements and instrumentalities shown. 
           [0008]      FIG. 1A  is an exploded perspective view of an embodiment of a cartridge utilizing an armor-piercing projectile. 
           [0009]      FIG. 1B  is a perspective view of the cartridge of  FIG. 1A . 
           [0010]      FIG. 1C  is a meplat end view of the armor-piercing projectile of  FIG. 1A . 
           [0011]      FIG. 1D  is a perspective view of a flute volume of the armor-piercing projectile of  FIG. 1A . 
           [0012]      FIG. 2A  is a first side view of the armor-piercing projectile of  FIG. 1A . 
           [0013]      FIG. 2B  is a second side view of the armor-piercing projectile of  FIG. 1A . 
           [0014]      FIG. 3  is a side sectional view of the armor-piercing projectile of  FIG. 1A . 
           [0015]      FIG. 4  depicts a perspective view of another example of an armor-piercing projectile. 
           [0016]      FIGS. 5A-5E  depict various views of another embodiment of an armor-piercing projectile. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIGS. 1A and 1B  are exploded perspective and perspective views, respectively, of an embodiment of a cartridge  100  utilizing an armor-piercing projectile  200 . These figures are described simultaneously, along with  FIG. 1C , which depicts a meplat end view of the armor-piercing projectile  200 . The cartridge  100  includes an annular casing  102  having a primer (not shown) disposed at a first end  104  thereof, as well-known in the art. The casing  102  includes an open second end  106  into which the projectile  200  is inserted during manufacture and assembly. The interior of the casing  102  is filled with a propellant (e.g., gunpowder) that is ignited by the primer. This ignition discharges the projectile  200  from a firearm, such as a handgun. In so-called “automatic weapons,” the force of the explosion is sufficient to both discharge the projectile and cycle a new cartridge into the weapon&#39;s firing chamber. The projectile  200  includes a body  202  that includes a plurality of fins  204  that form a meplat  206  of the projectile  200 . The meplat  206  is the generally flat leading surface of the projectile  200  that defines a plane P, which is substantially orthogonal to an axis A of the projectile  200 . In the depicted example, the projectile  200  includes three fins  204  that are spaced from each other by, and define, a corresponding number of longitudinal flutes  208 . Other numbers of fins and flutes are contemplated and are described herein. 
         [0018]    The fins  204  have a minimum thickness t (at the meplat  206 ) and expand as the distance from the meplat  206  increases. A thin minimum thickness t of the fins  204  at the meplat  206  helps the projectile more easily penetrate a barrier once fired from a firearm. The width w of the flutes  208  vary as the distance from the meplat plane P increases. In the depicted example, the flutes  208  are each defined by two curved surfaces  212  that also form surfaces of the fins  204 . Each curved surface  212  may be substantially constant in radius of curve time along its length (from the meplat  206  towards a base  226  of the projectile). In another example, the curved surfaces  212  may start a distance away from the meplat  206 , thus defining a meplat portion that has walls substantially parallel to the axis A, prior to beginning the curved surface  212 . These curved surfaces  212  intersect at an inner intersection curve  214  that is radially equidistant from adjacent fins  204 . As such, the flutes  208  are symmetrical. The flutes  208  are formed in a curved outer surface  216  (an ogive) of the projectile  200 . 
         [0019]    As depicted in  FIG. 1C , each flute  208  has an included angle α, which can vary as required or desired for a particular application, projectile caliber, and so on. The number of fins  204  may further limit the size of the included angle α. Each flute  208  may be defined by a flute volume V F , which is defined by a number of real surfaces and reference surfaces.  FIG. 1D  depicts the flute volume V F , which is defined by the two curved surfaces  212 , the plane P, and the reference outer surface  216 ′ (that is, the outer surface  216  that would be present but for the presence of the flute  208 ). For clarity, these the curved surfaces  212  intersect at the inner intersection curve  214 . Each curved surface  212  also intersects the curved outer surface  216  of the projectile  200  at outer intersection curves  218 . Additionally, each curved surface  212  intersects the plane P at a fin edge  220 , while the reference outer surface  216 ′ intersects the plane P at a meplat curve  222 . As such, these curves, edges, real surfaces, and reference surfaces substantially define the flute volume V F . 
         [0020]    The curved surfaces  212  define a curve generally along the axis A. That is, in the depicted examples, the curved surfaces  212  are curved from the fin edge  220  to a flute termination point  224 . In other examples, however, the curved surfaces  212  may also be curved from the outer intersection curve  218  to the inner intersection curve  214 . In such examples, the curved surfaces  212  would be concave. 
         [0021]    The armor-piercing projectile described herein may be manufactured as monolithic solid copper or brass. Other acceptable materials include copper, copper alloy, copper-jacketed lead, copper-jacketed zinc, copper-jacketed tin, powdered copper, powdered brass, powdered tungsten matrix, steel, stainless steel, aluminum, tungsten carbide, and like materials. The narrow minimum thickness t of the flutes  208  at the meplat  206  enable the projectile  200  to penetrate hard surfaces during flight. Thus, the projectiles described herein are barrier-blind to hide, hair, bone, clothing, drywall, car doors, etc. Barriers that would destroy a lead or lead-core projectile are easily breached with a projectile manufactured as described herein. The flutes  208  of the armor-piercing projectile generate large amounts of hydraulic force when the projectile  200  hits a so-called “wet target.” Wet targets include, for example, animals and persons, as well as water (in discharge testing tanks), and gel ordnance test blocks. As the projectile  200  moves forward within a wet target, fluid (water, blood, etc.) that enters the flutes  208  travels along and within the flutes  208  from the meplat  206  towards the flute termination point  224 . More accurately, as the projectile  200  moves forward in the wet target, fluid that is within the path of travel of the projectile  200  (e.g., within the flute volume V F ) is thrown violently outward due to hydraulic pressure as that fluid reaches the portions of the curved surfaces  212  proximate the termination point  224 . Thus, fluid that enters the flutes  208  is ejected therefrom by a strong hydraulic force. As such, the fluid is projected substantially radially outward from the axis A of the projectile  200 , creating a larger wound cavity and resulting in a cleaner kill. 
         [0022]      FIGS. 2A and 2B  are first and second side views, respectively, of the armor-piercing projectile  200  of  FIG. 1A . The projectile body  202  has a length L and a caliber Ø (e.g., the maximum body diameter). Each flute  208  has a flute depth D, as measured along an axis A of the projectile body  202 , from the meplat plane P to the termination point  224 . The meplat  206  has a meplat diameter Ø MEP  at the meplat plane P. The depicted projectile body  202  includes three flutes  208 , separated by an equal number of fins  204 . In other examples, a greater or fewer number of fins and flutes may be utilized as required or desired for a particular application. Projectiles having as few as two flutes/fins or as many as four flutes/fins are contemplated and are depicted herein. The fins  204  include a minimum thickness t at the meplat plane P. The minimum thickness t may be measured linearly across a width of the fin  204  at the meplat plane P.  FIG. 3  is a side sectional view of the armor-piercing projectile  200  of  FIG. 1A . The curved surface  212  of the flute  208  includes a curve radius r curve . A portion of the body  202  from the meplat plate P to proximate the termination point  224  is defined by a body radius r body . 
         [0023]    The relationships between the various components of the projectile  200  help ensure proper operation during firing and striking of a target. Once discharged from a firearm, the projectile  200  flies towards a target. When striking a wet target, fluid within the target is forced into the flutes  208 . This fluid continues to travel through the flutes  208 , towards a base  226  of the projectile  200 . As the fluid reaches the reference curve  212  proximate the termination point  224 , the fluid is forced outward (substantially radially away from the axis A), so as to create a large wound in the target. A chisel  226  (depicted by a dashed line in  FIG. 2A ) may be disposed proximate the meplat  206 . This chisel  226  further reduces the thickness t of the meplat  206 , thus improving barrier penetration. The chisel  226  is located such that the curved surface  212  does not begin until the end of the chisel  226 . 
         [0024]    The various dimensions of the components described above may be modified as required or desired for a particular application. Certain ratios have been discovered to be particularly beneficial to ensure significant cavity formation during contact with a wet target as well as to ensure proper feeding from a magazine of an automatic weapon. For example, the flute depth D, as measured along axis A from the meplat plane P may be between about 50% to about 55% of the total projectile length L. In another example, the flute depth D may be about 52% of the total projectile length L. The meplat diameter Ø MEP  at the meplat plane P may be between about 50% to about 55% of the maximum body diameter Ø (e.g., the caliber). In a more specific example, the meplat diameter Ø MEP  may be about 52% of the maximum body diameter Ø. Such a meplat diameter Ø MEP  allows the cartridge to be fed in an automatic weapon without interference. Other geometric relationships are contemplated and are described below. The dimensions of the various portions of the disclosed projectiles assist in enabling those projectiles to function properly when hitting a wet target. 
         [0025]      FIG. 4  depicts a perspective view of another example of an armor-piercing projectile. A number of components are depicted and described above in previous figures and as such are not necessarily described further. In relevant part, the projectile  300  includes four flutes  308  and four fins  304 . An included angle α is about 90°. Geometric relationships for a four flute/fin configuration are depicted below. 
         [0026]    Table 1 depicts geometric relationships for projectiles having fins and flutes as described herein. In general, these geometric relationships enable a projectile to transmit sufficient force as it enters a wet target so as to create a cavity. Geometric relationships outside these ranges may not transmit sufficient force to the wet target and, as such, may not produce a desired cavity. In certain examples, however, geometric relationships outside of these ranges may, in fact, produce the desired results. In that regard, Table 1 depicts a number of exemplary relationships that have been discovered to be desirable, but other relationships and dimensions are contemplated and may be achieved by a person of skill in the art without undue experimentation, based on the disclosure provided herein. More specifically, the optimum flute volume V F  is depicted for a three flute configuration. The minimum flute volume V F  is generally the minimum required to produce the desired cavity in a wet target. For a three flute example, a flute included angle α of about 120° is desirable. Two flute configurations may have an included angle of about 150°, while four flute configurations may have an included angle of about 90°. It has also been determined that a fin width t greater than 0.05″ may prevent the projectile from adequately penetrating barriers. The meplat diameter φ MEP  is not depicted but may vary depending on the configuration of the firearm firing the projectile. In general, it is desirable that the meplat diameter φ MEP  is as large as possible while still being able to be fed within the firearm. In examples, the meplat diameter φ MEP  is about 45% to about 55% of the outside diameter φ. In another examples, a meplat diameter φ MEP  of about 50% or about 52% of the outside diameter φ may be desirable. Projectiles having weights of up to about 75 grains, 78 grains, 105 grains, and so on, are contemplated. For example, a projectile of less than 75 grains with a diameter φ of about 0.353″ to about 0.359″ is contemplated. In another example, a projectile of less than 105 grains with a diameter φ of about 0.399″ to about 0.404″ is contemplated. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 FLUTED PROJECTILE GEOMETRY RELATIONSHIPS 
               
             
          
           
               
                   
                 Flute 
                   
                   
               
               
                 Outside 
                 Volume V F  (cc) 
                   
                 Fin Width t (in) 
               
             
          
           
               
                 Diameter φ 
                 Opti- 
                 Mini- 
                 Flute Included 
                 Flute 
                 Opti- 
                 Mini- 
               
               
                 (in) 
                 mum 
                 mum 
                 Angle α (°) 
                 Number 
                 mum 
                 mum 
               
               
                   
               
             
          
           
               
                 0.312 
                 0.112 
                 0.075 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                 0.355 
                 0.128 
                 0.086 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                 0.4 
                 0.144 
                 0.097 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                 0.429 
                 0.151 
                 0.104 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                 0.451 
                 0.162 
                 0.109 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                 0.452 
                 0.162 
                 0.109 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                 0.5 
                 0.216 
                 0.145 
                 90-150 
                 2-4 
                 0.026 
                 0.05 
               
               
                   
               
             
          
         
       
     
       Example 1 
       [0027]    In a view of the geometric relationships depicted in Table 1, an example projectile consistent therewith is presented in  FIGS. 5A-5E . The reference numerals utilized in  FIGS. 5A-5E  are consistent with those depicted above. Accordingly, those elements are generally not necessarily described further. The projectile  500  is manufactured to the following specifications, identified in Table 2 below. Manufacturing tolerances are not reflected in the figures or Table 2. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 EXAMPLE 1 DIMENSIONS 
               
             
          
           
               
                   
                 Dimension 
                 Inches (unless noted) 
               
               
                   
                   
               
             
          
           
               
                   
                 Body Length, L 
                 0.505 
               
               
                   
                 Body Caliber, Ø 
                 0.40 
               
               
                   
                 Meplat Diameter, Ø MEP   
                 0.212 
               
               
                   
                 Flute Length, L F   
                 0.277 
               
               
                   
                 Curved Surface Radius, r curve   
                 0.3125 
               
               
                   
                 Outer Surface Radius, r body   
                 0.424 
               
               
                   
                 Fin Minimum Thickness, t 
                 0.026 
               
               
                   
                 Flute Volume, V F   
                 0.144 cc 
               
               
                   
                 Included Angle, α 
                 120° 
               
               
                   
                   
               
             
          
         
       
     
         [0028]    The projectile described in accordance with EXAMPLE 1 was discharged at a subsonic velocity from a weapon into a 10% ordnance gelatin test block. The results of this test are presented below. 
       Test Summary: 
       [0029]    A 78 gr projectile (as described in EXAMPLE 1) was used. The projectile was fired from a Browning Hi-Power Pistol having a barrel length of 4.75″. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Projectile Specification: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Weight 
                 78 gr 
               
               
                   
                 Length 
                 0.505″ 
               
               
                   
                 Flutes 
                 3 at 120° 
               
               
                   
                   
               
             
          
         
       
     
       Ordnance Gel Specification: 
       [0030]    The projectile was discharged into a 10% ballistic ordnance gelatin test block manufactured and calibrated in accordance with the FBI Ammunition Testing Protocol, developed by the FBI Academy Firearms Training Unit. The base powder material utilized for the 10% ordnance gelatin test block was VYSE™ Professional Grade Ballistic &amp; Ordnance Gelatin Powder available from Gelatin Innovations, of Schiller Park, Ill. The block was manufactured at the test site in accordance with the formulations and instructions provided by the powder manufacturer. After manufacture of the gelatin test block, the test block was calibrated. Calibration requires discharging a 0.177 steel BB at 584 feet per second (fps), plus or minus 15 fps, into the gelatin test block. The test block is considered calibrated if the shot penetrates 8.5 centimeters (cm), plus or minus 1 cm (that is, 2.95 inches-3.74 inches). The calibrated block is then used in the terminal performance testing of the projectile. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Terminal Performance Testing: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Shot Velocity 
                 1,630 fps 
               
               
                   
                 Temporary Cavity (TC) Length 
                 14″ approximate 
               
               
                   
                 TC Max. Diameter 
                 4.125″ approximate 
               
               
                   
                 Length of TC at Max. Diameter 
                 3.75″ approximate 
               
               
                   
                 Maximum Penetration Depth 
                 17.75″ approximate 
               
               
                   
                 Projectile Weight Retained 
                 78 gr 
               
               
                   
                 Average Projectile Expansion Diameter 
                 0.353″ approximate 
               
               
                   
                 Largest Projectile Diameter 
                 0.355″ approximate 
               
               
                   
                   
               
             
          
         
       
     
         [0031]    As can be seen, there is very little change in the diameter of the projectile, which indicates that the projectile does not deform upon impact. As such, the cavity is formed by the hydraulic forces caused by the expulsion of fluid from the flutes. The projectile, when utilized in a cartridge having an appropriate casing and primer, can be fed from a magazine of virtually any capacity, in both automatic and semi-automatic weapons. 
         [0032]    Manufacture of projectiles consistent with the technologies described herein may be by processes typically used in the manufacture of other projectiles. The projectiles may be cast from molten material, or formed from powdered metal alloys. Projections in the mold may form the depicted flutes, or the flutes may be cut into the projectiles after casting. The projectiles, casings, primers, and propellants may be assembled using one or more pieces of automated equipment. 
         [0033]    Unless otherwise indicated, all numbers expressing dimensions, speed, weight, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present technology. 
         [0034]    As used herein, “about” refers to a degree of deviation based on experimental error typical for the particular property identified. The latitude provided the term “about” will depend on the specific context and particular property and can be readily discerned by those skilled in the art. The term “about” is not intended to either expand or limit the degree of equivalents that may otherwise be afforded a particular value. Further, unless otherwise stated, the term “about” shall expressly include “exactly,” consistent with the discussions regarding ranges and numerical data. Lengths, sizes, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. This same principle applies to ranges reciting only one numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described. 
         [0035]    Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. 
         [0036]    While there have been described herein what are to be considered exemplary and preferred embodiments of the present technology, other modifications of the technology will become apparent to those skilled in the art from the teachings herein. The particular methods of manufacture and geometries disclosed herein are exemplary in nature and are not to be considered limiting. It is therefore desired to be secured in the appended claims all such modifications as fall within the spirit and scope of the technology. Accordingly, what is desired to be secured by Letters Patent is the technology as defined and differentiated in the following claims, and all equivalents.