Reduced drag projectiles

Abstract

Embodiments of the invention include an elongate rifle bullet with a plurality of circumferential grooves having overmolded polymer therein defining embedded polymer rings. Embodiments of the invention include cartridges with propellant and such bullets. In one or more embodiments, the bullet has a body portion and a converging nose portion. The polymer rings have an outer surface that is flush with, that is, conforming to the outer surface of the body. The polymer may have be selected to have a favorable coefficient of friction with respect to the barrel. A feature and advantage of embodiments is that the metal to metal contact between the bullet and the barrel is reduced while not diminishing the ballistic coefficient of the bullet.

Claims

1. A method of manufacturing a bullet of .50 caliber or less, the method comprising: obtaining a bullet body defining a plurality of circumferential grooves, each circumferential groove having a pair of adjacent wall portions, the bullet body comprising a body wall extending between an interior wall surface and an exterior wall surface, the interior wall surface defining an interior cavity, the interior cavity fluidly communicating with an opening defined by a forward facing edge of the bullet body, the interior cavity extending rearwardly from the opening to a cavity end point within the bullet body, a core member disposed inside the cavity, the core member comprising a forward facing surface, the core member extending rearwardly from the forward facing surface to the cavity end point within the body, the forward facing surface of the core member and the interior wall surface defining a forward portion of the interior cavity, the forward portion of the interior cavity having a cavity radius, the cavity radius decreasing as the forward portion of the interior cavity extends forward from the forward facing surface of the core member to the opening; inserting the bullet body into a mold with one or more groove sprues, the mold having a mold wall surface that is flush at the location of each of the plurality of grooves and the exterior wall surface at the respective adjacent wall portions to each of the plurality of grooves; injecting molten polymer into the plurality of grooves through the one or more groove sprues; allowing the polymer to cool forming a plurality of polymer bands, each polymer band being disposed in one of the plurality of circumferential grooves; and removing the bullet body from the mold.

2. The method of claim 1 further comprising: injecting molten polymer into the forward portion of the interior cavity through at least one tip sprue; and allowing the polymer to cool forming a polymer tip, the polymer tip comprising a forward portion extending forward of the opening and a rearward portion extending rearward of the opening, the rearward portion having a shape corresponding to the forward portion of the interior cavity to retain the polymer tip in place.

3. The method of claim 2 wherein molten polymer is injected into the plurality of grooves through the one or more groove sprues into the plurality of grooves while molten polymer is being injected into the forward portion of the interior cavity through the at least one tip sprue.

4. The method of claim 1 further comprising providing a mold defining a tip cavity fluidly communicating with at least one tip sprue.

5. The method of claim 2, further comprising selecting a mold wherein each of the one or more groove sprues is in fluid communication with the at least one tip sprue.

6. A method of manufacturing a bullet of .50 caliber or less, the method comprising: providing a bullet body defining a plurality of circumferential grooves, each circumferential groove being defined by a groove root surface of the bullet body and a pair of opposing groove side surfaces, each opposing groove side surface extending between the groove root surface and a barrel engaging surface of the bullet body, wherein the bullet body is continuous and of a single material when viewed as a cross-section with a section plane passing through the groove root surface; inserting the bullet body into a mold with one or more groove sprues, the mold having a mold wall surface that is flush at the location of each of the plurality of grooves and an exterior bullet body wall surface at the respective adjacent wall portions of each of the plurality of grooves; injecting molten polymer into the plurality of grooves through the one or more groove sprues; allowing the polymer to cool forming a plurality of polymer bands, each polymer band being disposed in one of the plurality of circumferential grooves and having an exterior surface flush with the exterior bullet wall surface; removing the bullet body from the mold; and inserting the bullet body into a casing with propellant in the casing.

7. The method of claim 6 further comprising providing the bullet body as monolithic and of a single material.

8. The method of claim 7 further comprising selecting the single material of the bullet body to be copper or a copper alloy.

9. The method of claim 6 further comprising integrally forming the bullet body from a unitary piece of material.

10. The method of claim 6 further comprising selecting a polymer to have a minimal coefficient of friction with respect to the steel barrel.

11. The method of claim 6 further comprising heating the bullet body prior to the injection of the polymer whereby the polymer adhesion to the bullet body is enhanced.

12. The method of claim 6 further comprising undercutting each of the plurality of grooves.

13. A method of manufacturing a bullet of .50 caliber or less, the method comprising: providing a bullet body defining a plurality of circumferential grooves, each circumferential groove being defined by a groove root surface of the bullet body and a pair of opposing groove side surfaces, each opposing groove side surface extending between the groove root surface and a barrel engaging surface of the bullet body, wherein the bullet body is continuous when viewed as a cross-section with a section plane passing through the groove root surface and the bullet body has no separate core at the cross-section; inserting the bullet body into a mold with one or more groove sprues, the mold having a mold wall surface that is flush at the location of each of the plurality of grooves and an exterior bullet body wall surface at the respective adjacent wall portions of each of the plurality of grooves; injecting molten polymer into the plurality of grooves through the one or more groove sprues; allowing the polymer to cool forming a plurality of polymer bands, each polymer band being disposed in one of the plurality of circumferential grooves and having an exterior surface flush with the exterior bullet wall surface; removing the bullet body from the mold; and inserting the bullet body into a casing with propellant in the casing.

14. The method of claim 13 further comprising providing the bullet body as monolithic and of a single material.

15. The method of claim 14 further comprising selecting the single material of the bullet body to be copper or a copper alloy.

16. The method of claim 13 further comprising integrally forming the bullet body from a unitary piece of material.

17. The method of claim 13 further comprising selecting a polymer to have a minimal coefficient of friction with respect to the steel barrel.

18. The method of claim 13 further comprising heating the bullet body prior to the injection of the polymer whereby the polymer adhesion to the bullet body is enhanced.

19. The method of claim 13 further comprising undercutting each of the plurality of grooves.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The drawings included in the present application are incorporated into, and form part of, the specification. They illustrate embodiments of the present disclosure and, along with the description, serve to explain the principles of the disclosure. The drawings are only illustrative of certain embodiments and do not limit the disclosure.

(2) FIG. 1 depicts a side elevation view of rifle bullet, according to one or more embodiments.

(3) FIG. 2 is a cross-sectional view of the bullet of FIG. 1.

(4) FIG. 3 depicts a side elevation view of the bullet body of FIG. 1 before the overmolding process.

(5) FIG. 4 depicts a cross-sectional illustrating a bullet and casing and the respective interface according to one or more embodiments.

(6) FIG. 5 is a cross-sectional view of mold with a bullet therein prior to overmolding polymer bands thereon.

(7) FIG. 6 is a cross-sectional view of mold with a bullet therein prior to overmolding polymer bands thereon.

(8) FIG. 7 is a cross-sectional view of mold with a bullet therein prior to overmolding polymer bands thereon.

(9) FIG. 8 is an exploded perspective view of a bullet in accordance with the detailed description.

(10) FIG. 9 is an exploded perspective view of a bullet in accordance with the detailed description.

(11) FIG. 10 is an enlarged perspective view further illustrating the tip member of the bullet shown in FIG. 9.

(12) FIG. 11A is an enlarged perspective view further illustrating the tip member of the bullet shown in FIG. 8.

(13) FIG. 11B is an enlarged side view further illustrating the tip member of the bullet shown in FIG. 11A.

(14) FIG. 12 is a perspective view showing a projectile body in accordance with the detailed description.

(15) FIG. 13 is a perspective view of a projectile body in accordance with the detailed description. In the embodiment of FIG. 13, the projectile body has been sectioned along a plane YZ and a plane XZ.

(16) FIG. 14 is an enlarged perspective view of the projectile body shown in FIG. 13.

(17) FIG. 15 is a cross-sectional view of the projectile body shown in FIG. 13 and FIG. 14.

(18) FIG. 16A is a side view of a projectile body in accordance with the detailed description.

(19) FIG. 16B is a cross-sectional view of the projectile body shown in FIG. 16A taken along section line B-B shown in FIG. 16A.

(20) FIG. 16C is a cross-sectional view of the projectile body shown in FIG. 16A taken along section line C-C shown in FIG. 16A.

(21) FIG. 16D is a cross-sectional view of the projectile body shown in FIG. 16A taken along section line D-D shown in FIG. 16A.

(22) FIG. 16E is a cross-sectional view of the projectile body shown in FIG. 16A taken along section line E-E shown in FIG. 16A.

(23) FIG. 17A is a side view of a tip member in accordance with the detailed description.

(24) FIG. 17B is a cross-sectional view of the tip member shown in FIG. 17A taken along section line B-B shown in FIG. 17A.

(25) FIG. 18 is a cross-sectional view of a projectile including a projectile body and a tip member.

(26) FIG. 19A depicts a side elevation view of rifle bullet, according to one or more embodiments.

(27) FIG. 19B is a cross-sectional view of the bullet shown in FIG. 19A.

(28) FIG. 19C depicts a side elevation view of the bullet body shown in FIG. 19A before the overmolding process.

(29) FIG. 20A depicts a side elevation view of rifle bullet, according to one or more embodiments.

(30) FIG. 20B is a cross-sectional view of the bullet shown in FIG. 20A.

(31) FIG. 20C depicts a side elevation view of the bullet body shown in FIG. 20A before the overmolding process.

(32) FIG. 21A depicts a side elevation view of rifle bullet, according to one or more embodiments.

(33) FIG. 21B is a cross-sectional view of the bullet shown in FIG. 21A.

(34) FIG. 21C depicts a side elevation view of the bullet body shown in FIG. 21A before the overmolding process.

(35) FIG. 22 is a cross-sectional view of an assembly including a cartridge case.

(36) FIG. 23 is a cross-sectional view of a cartridge including a cartridge case and a projectile.

(37) While embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

(38) Referring to FIGS. 1-3, a side view of rifle bullet 20 is depicted according to one or more embodiments. The bullet 20 has a body 22 with a main body portion 24 and a nose portion 32. In one or more embodiments, the main body portion 24 comprises a tail portion 102 and a barrel engaging portion 104. Additionally, the bullet 20 may include a polymer tip 36 in a forward cavity 38 of the nose portion 32. The bullet main body portion and nose portion in one or more embodiments are monolithic. In one or more embodiments, the bullet 20 has one or more circumferentially extending grooves 44. The grooves having polymer bands 46 therein formed by overmolding. The grooves may have square corners but also other shapes including an undercut shape are within the scope of the invention. That is, the cross section of the groove and the band molded therein may be, by way of example and not limitation, trapezoidal shaped in lateral cross-section and/or a C-shape cut. The grooves are contemplated to extend inwardly 4 to 15% of the diameter of the main body portion adjacent to the groove. In one or more embodiments, there pa be 1, 2, 3, 4, or 5 grooves. In one or more embodiments there may be a single groove. In one or more embodiments a monolithic body portion, tail portion and nose portion are formed of unalloyed copper, a copper alloyed with another metal, or other metal.

(39) Referring to FIG. 4, a bullet 20 according to embodiments of the invention is seated in a casing 50. An upper lip 52 of the casing 50 may be aligned and slightly swaged inwardly at one of the bands whereby a very secure high integrity seal with respect to the interior of the casing and the propellant may be formed.

(40) Referring to FIG. 5, a mold 60 is illustrated with two mold halves 62, 64, and with nozzle ports 70, 72 for injection molding molten polymers, and with sprues 76, 78. The sprues 76 leading to the grooves in the bullet body 80 effect the overmolding of the bands in the grooves. The sprue 78 provide the molten polymer for the overmolded tip. In one or more embodiments, the mold wall surface 79 is flush at the location of the grooves and the adjacent body portions.

(41) As overmolded or inserted, the polymer tip 36 has an exterior surface 84 substantially flush with an exterior surface 86 of the bullet for forming a relatively streamlined or spitzer aerodynamic shape. In one or more embodiments, the front cavity 90 may have an undercut portion 92 for providing a mechanical lock for the tip.

(42) The bullet may be conventionally formed up to the overmolding process. In the overmolding process, the bullet is put in the mold, the mold is closed, and the polymer is injected into the groove and other recess in the bullet that are being overmolded.

(43) Once injected, the mold 60 applies a holding pressure to the bullet body 80 and the injected thermoplastic material to reduce potential air pockets and for completely filling the grooves 44 and/or the tip cavity 90 with thermoplastic material. As pressure is applied, the mold and thermoplastic material begin to cool and the thermoplastic material solidifies. In one or more embodiments, cooling is expedited by convection due to coolant flowing through cooling lines 208 inside the mold 60. The mold is opening and the bullet removed. Sprue pieces may be trimmed from the bullet as needed.

(44) Referring to FIG. 6, a mold 60 comprising two mold halves 62, 64 is shown. The mold 60 also includes two nozzle ports 70, 72 and sprues 76, 78 for injection molding molten polymers. The sprues 76 leading to the grooves in the bullet body 80 effect the overmolding of the bands in the grooves. The sprue 78 provides molten polymer to a tip cavity for forming a polymer tip. In one or more embodiments, the mold wall surface 79 is flush at the location of the grooves and the adjacent body portions. In one or more embodiments, a front cavity 90 defined by the bullet body 80 includes an undercut portion 92 for providing a mechanical lock with the polmyer tip. In overmolding processes, in accordance with one or more embodiments, the bullet body 80 is put in the mold, the mold is closed, and the polymer is injected into the groove(s) and other cavities in the bullet that are being overmolded. Once molten thermoplastic material is injected into the mold 60, the mold 60 applies a holding pressure to the bullet body 80 and the injected thermoplastic material to reduce potential air pockets and for completely filling the grooves 44 and/or the tip cavity 90 with thermoplastic material. As pressure is applied, the mold and thermoplastic material begin to cool and the thermoplastic material solidifies. In one or more embodiments, cooling is expedited by convection due to coolant flowing through cooling lines the mold. The mold is opening and the bullet removed. Sprue pieces may be trimmed from the bullet as needed.

(45) Referring to FIG. 7, a mold 60 comprising two mold halves 62, 64 is shown. The mold 60 also include a nozzle port 74 and sprues 76, 78 for injection molding molten polymers. The sprues 76 leading to the grooves in the bullet body 80 effect the overmolding of the bands in the grooves. The sprue 78 provides molten polymer to a tip cavity for forming a polymer tip. In one or more embodiments, the mold wall surface 79 is flush at the location of the grooves and the adjacent body portions. In one or more embodiments, a front cavity 90 defined by the bullet body 80 includes an undercut portion 92 for providing a mechanical lock with the polmyer tip. In the example embodiment of FIG. 7, the sprue 76 and the sprue 79 are in fluid communication with one another. Also in the embodiment of FIG. 7, the front cavity 90 is in fluid communication with the grooves defined by the bullet body 80 via the sprues 76, 78.

(46) Referring to FIGS. 1 through 21C, a projectile 20 comprises a projectile body 100, one or more polymer bands 44 and a polymer tip member 36. In one or more embodiments, the projectile body 100 includes a tail portion 102, a nose portion 106 and a barrel engaging portion 104 extending rearwardly between the nose portion 106 and the tail portion 102. In one or more embodiments, the portions of the projectile body 100 are arranged along a central longitudinal axis 122. In one or more embodiments, the tail portion 102 has a rearward facing surface 124 defining an XY plane. In these embodiments, the tail portion 102 extends forwardly along the central longitudinal axis 122 of the projectile body 100 between the rearward facing surface 124 and the barrel engaging portion 104. In one or more embodiments, the central longitudinal axis 122 is orthogonal to the XY plane. In one or more embodiments, the tail portion 102 has a tail radius 220 extending between the central longitudinal axis 122 and an outer tail surface 320 of the tail portion 102. In one or more embodiments, the tail radius 220 increases as the tail portion 102 extends forwardly along the central longitudinal axis 122.

(47) In one or more embodiments, the barrel engaging portion 104 of the projectile body 100 extends forwardly along the central longitudinal axis 122 between the tail portion 102 and the nose portion 106. The barrel engaging portion 104 has a barrel engaging radius 222 extending between the central longitudinal axis 122 and a barrel engaging surface 322 of the barrel engaging portion 104. In one or more embodiments, the barrel engaging portion 104 defines one or more circumferential grooves 44. In one or more embodiments, the projectile 20 comprising one or more polymer bands 46 with each polymer band 46 being disposed in one of the circumferential grooves 44 defined by the barrel engaging portion 104.

(48) In one or more embodiments, the nose portion 106 of the projectile body 100 comprising a forward facing edge 148 defining an opening 150. In one or more embodiments, the nose portion 106 extends forwardly along the central longitudinal axis 122 between the barrel engaging portion 104 and the forward facing edge 148. In one or more embodiments, the nose portion 106 has a nose radius 224 extending between the central longitudinal axis 122 and an outer nose surface 324 of the nose portion 106. In one or more embodiments, the nose radius 224 decreases as the nose portion 106 extends forwardly along the central longitudinal axis 122. In one or more embodiments, the nose portion has a shape generally corresponding to the shape of an ogive.

(49) In one or more embodiments, the projectile body 100 comprises a body wall 160 extending between an interior wall surface 162 and an exterior wall surface 164. In one or more embodiments, the interior wall surface 162 defines an interior cavity 152 and the interior cavity fluidly communicates with the opening 150 defined by the forward facing edge 148 of the nose portion 106. In one or more embodiments, the interior cavity 152 extends rearwardly from the opening 150 to a cavity end point 154 within the projectile body 100.

(50) In one or more embodiments, a core member 240 is disposed inside the interior cavity 152. In one or more embodiments, the core member 240 comprises a forward facing surface 242 and the core member 240 extends rearward from the forward facing surface 242 to the interior cavity end point 154 within the projectile body 100. In one or more embodiments, the forward facing surface 242 of the core member 240 and the interior wall surface 162 define a forward portion 252 of the interior cavity 152. In one or more embodiments, the forward portion 252 of the interior cavity 152 has a cavity radius 226 that decreases as the forward portion 252 of the interior cavity 152 extends forward from the forward facing surface 242 of the core member 240 to the opening 150.

(51) In one or more embodiments, the projectile 20 includes a tip member 36 extending through the opening 150. In one or more embodiments, the tip member 36 has a distal portion 362 extending forward of the opening 150 and a proximal portion 364 extending rearward of the opening 150. In one or more embodiments, the proximal portion 364 of the tip member 36 has a tip retention radius 228 extending between the central longitudinal axis 122 and a tip retention surface 328 of the proximal portion 364 of the tip member 36. In one or more embodiments, the tip retention radius 228 increases as the proximal portion 364 of the tip member 36 extends rearward from the opening 150 to the forward facing surface 242 of the core member 240.

(52) In one or more embodiments, each circumferential groove 44 is partially defined by a groove root surface 330. In one or more embodiments, each groove root surface 330 has a groove root radius 230 extending between the central longitudinal axis 122 and the groove root surface. In one or more embodiments, the barrel engaging portion 104 has a barrel engaging radius 222 extending between the central longitudinal axis 122 and a barrel engaging surface 322 of the barrel engaging portion 104. In one or more embodiments, the barrel engaging portion 104 defines one or more circumferential grooves 44. In one or more embodiments, each circumferential groove 44 has a groove depth extending between the groove root surface 330 and the barrel engaging surface 322. In one or more embodiments, the projectile 20 comprising one or more polymer bands 46 with each polymer band 46 being disposed in one of the circumferential grooves 44 defined by the barrel engaging portion 104. In one or more embodiments, each polymer band 46 has a band thickness extending between the groove root surface 330 and the barrel engaging surface 322.

(53) In an embodiment, the barrel engaging radius is between 0.07 inches and 0.25 inches. In an embodiment, the barrel engaging radius is between 0.08 inches and 0.18 inches. In an embodiment, the projectile body is integrally formed from a unitary piece of metal. In an embodiment, the projectile body comprises a metal. In an embodiment, the projectile body comprises copper. In an embodiment, the projectile has a weight between 30 grains and 300 grains. In an embodiment, the projectile has a weight between 50 grains and 200 grains.

(54) Referring to FIG. 22 and FIG. 23, an ammunition cartridge 400 in accordance with one or more embodiments comprises a case 408 comprising a base portion 422 and a case wall 424 extending forward from the base portion 422 to a forward edge 428 of the case wall 424. An inner surface 426 of the case wall 424 defines a lumen 430, the lumen extending rearward from the forward edge 428 toward the base portion 422. In an embodiment, the base portion 422 and the inner surface 426 of the case wall 424 define a cavity 432 and the cavity 432 fluidly communicates with the lumen 430. In an embodiment, the inner surface 426 of the case wall 424 defines an opening 434 proximate the forward edge 428 of the case wall 424, the opening 434 fluidly communicating with the lumen 430. In an embodiment, a propellant charge 436 is disposed inside the cavity 432 for producing a quantity of propellant gas and a primer housing 438 is disposed in a hole 440 defined by the base portion 422 of the case 408, a priming material disposed inside the primer housing 438 for igniting the propellant charge 436. The ammunition cartridge also comprises a projectile 420 comprising a projectile body 100 including a tail portion 102, a nose portion 106, and a barrel engaging portion 104 extending rearwardly between the nose portion 106 and the tail portion 102, the portions of the projectile body 100 being arranged along a central longitudinal axis 122. In an embodiment, the barrel engaging portion 104 of the projectile body 100 extends forwardly along the central longitudinal axis 122 between the tail portion 102 and the nose portion 106. In an embodiment, the barrel engaging portion 104 defines one or more circumferential grooves 44. In an embodiment, the projectile 420 comprises a polymer band 46 disposed in the circumferential groove 44 defined by the barrel engaging portion 104 of the projectile body 100. In an embodiment, the projectile body 100 is positioned to extend through the lumen 430 defined by the inner surface 426 of the case wall. In an embodiment, the projectile body 100 is positioned so that a plane P defined by the forward edge 428 of the case wall 424 passes through the polymer band 46 disposed in the circumferential groove 44 defined by the barrel engaging portion 104 of the projectile body 100. In an embodiment, an upper portion of the case wall 424 is swaged or crimped inwardly to form a seal between the case wall 424 and the projectile 420 for closing the opening 434 and preventing fluid communication between the propellant charge 436 in the cavity 432 and an atmosphere outside of the ammunition cartridge 400.

(55) The following United States patents are hereby incorporated by reference herein: U.S. Pat. Nos. 3,881,421, 4,044,685, 4,655,140, 4,685,397, 5,127,332, 5,259,320, 535,101, 6,070,532, and 8,186,277.

(56) The following United States patents are hereby incorporated by reference herein:

(57) U.S. Pat. Nos. 1,080,974, 1,135,357, 1,493,614, 1,328,334, 1,967,416, 375,158, 5,454,325, 6,317,946 and 7,380,502.

(58) The above references in all sections of this application are herein incorporated by references in their entirety for all purposes. Components illustrated in such patents may be utilized with embodiments herein. Incorporation by reference is discussed, for example, in MPEP section 2163.07(B).

(59) All of the features disclosed in this specification (including the references incorporated by reference, including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

(60) Each feature disclosed in this specification (including references incorporated by reference, any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

(61) The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any incorporated by reference references, any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed The above references in all sections of this application are herein incorporated by references in their entirety for all purposes.

(62) Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose could be substituted for the specific examples shown. This application is intended to cover adaptations or variations of the present subject matter. Therefore, it is intended that the invention be defined by the attached claims and their legal equivalents, as well as the following illustrative aspects. The above described aspects embodiments of the invention are merely descriptive of its principles and are not to be considered limiting. Further modifications of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention.