Expanding subsonic bullet

Abstract

A bullet designed to expand reliably at subsonic velocities has a leading end region divided by notches into petals. The exterior of the bullet has a groove configured to allow limited initial bending of the petals to facilitate spreading of the petals to increase the cross-section of the bullet upon impact with a target.

Claims

1. A bullet comprising: an elongated body having a body leading region, with a leading face and a leading region exterior surface, and having a body trailing region, said body being symmetrically disposed about a longitudinal central axis; a cavity formed in said body leading region, said cavity terminating at said leading face and extending therefrom towards said body trailing region; a plurality of longitudinal notches extending radially outward from said cavity, said notches dividing at least a portion of said body leading region into a plurality of petals separated from each other by said notches; and a groove in said leading region exterior surface and traversing each petal so as to divide said petal between a petal forward section, extending from said groove to said forward face, and a petal base section extending rearward from said groove, said petal forward section having a petal forward inner surface that defines a portion of said cavity, said groove being configured to act as a living hinge that allows said petal forward section to bend relative to said petal base section under hydraulic forces, but which arrests such bending when said petal forward inner surface reaches a specified angle with respect to the longitudinal axis, wherein said forward region exterior surface has a pressure-reducing section extending forward from said groove, said pressure-reducing section acting to reduce pressure in a region surrounding at least a portion of said petal forward sections that extend forward from said groove, and wherein said forward region exterior surface rearward of said groove has an ogive profile, and said pressure-reducing section has a profile that is discontinuous compared to an extension of said ogive profile.

2. The bullet of claim 1 wherein said pressure-reducing section has at least a portion that is cylindrical.

3. The bullet of claim 1 wherein said leading face further comprises: a rearward-sloping surface forming a funnel-shape terminating at said cavity.

4. The bullet claim 1 wherein each of said notches extends between said cavity and said forward region exterior surface.

5. The bullet claim 1 wherein each of said notches is radially oriented, such that a projection of said notch intersects the longitudinal axis.

6. The bullet claim 1 wherein each of said notches is angled with respect to a radial orientation when viewed looking toward said leading face, such that a projection of said notch does not intersect the longitudinal axis.

7. The bullet of claim 1 wherein said groove is configured to act as a living hinge that allows said petal forward section to bend relative to said petal base section under hydraulic forces, but which arrests such bending when said petal forward section rear edge is brought into contact with another surface of said groove.

8. The bullet of claim 1 wherein said groove is positioned closer to said leading face than to an end of said body trailing region, as measured along the longitudinal central axis.

9. The bullet of claim 8 wherein said groove is positioned closer to said leading face than to a midpoint between said leading face and the end of said body trailing region, as measured along the longitudinal central axis.

10. A bullet comprising: an elongated body having a body leading region, with a leading face and a leading region exterior surface, and having a body trailing region, said body being symmetrically disposed about a longitudinal central axis; a cavity formed in said body leading region, said cavity terminating at said leading face and extending therefrom towards said body trailing region; a plurality of longitudinal notches extending radially outward from said cavity, said notches dividing at least a portion of said body leading region into a plurality of petals separated from each other by said notches; and a groove in said leading region exterior surface and traversing each petal so as to divide said petal between a petal forward section, extending from said groove to said forward face, and a petal base section extending rearward from said groove, said petal forward section having a petal forward inner surface that defines a portion of said cavity, said groove being configured to act as a living hinge that allows said petal forward section to bend relative to said petal base section under hydraulic forces, but which arrests such bending when said petal forward inner surface reaches a specified angle with respect to the longitudinal axis, wherein said forward region exterior surface has a pressure-reducing section extending forward from said groove, said pressure-reducing section acting to reduce pressure in a region surrounding at least a portion of said petal forward sections that extend forward from said groove, and wherein said pressure-reducing section has a pressure section front diameter D.sub.F and a pressure section rear diameter D.sub.R where the pressure-reducing section terminates at the groove, with these diameters (D.sub.F, D.sub.R) selected such that D.sub.F>D.sub.R.

11. A bullet comprising: an elongated body having a body leading region, with a leading face and a leading region exterior surface, and having a body trailing region, said body being symmetrically disposed about a longitudinal central axis; a cavity formed in said body leading region, said cavity terminating at said leading face and extending therefrom towards said body trailing region; a plurality of longitudinal notches extending radially outward from said cavity, said notches dividing at least a portion of said body leading region into a plurality of petals separated from each other by said notches; and a groove in said leading region exterior surface and traversing each petal so as to divide said petal between a petal forward section, extending from said groove to said forward face, and a petal base section extending rearward from said groove, said groove intersecting said forward region exterior surface along a petal forward section rear edge on said petal forward section, said groove being configured to act as a living hinge that allows said petal forward section to bend relative to said petal base section under hydraulic forces, but which arrests such bending at a predetermined angle when such bending brings said petal forward section rear edge into contact with another surface of said groove, wherein said forward region exterior surface has a pressure-reducing section extending forward from said groove, said pressure-reducing section acting to reduce pressure in a region surrounding at least a portion of said petal forward sections that extend forward from said groove, and wherein said forward region exterior surface rearward of said groove has an ogive profile, and said pressure-reducing section has a profile that is discontinuous compared to an extension of said ogive profile.

12. The bullet of claim 11 wherein said pressure-reducing section has at least a portion that is cylindrical wherein D.sub.F=D.sub.R.

13. The bullet of claim 11 wherein said leading face further comprises: a rearward-sloping surface forming a funnel-shape terminating at said cavity.

14. The bullet of claim 11 wherein each of said notches extends between said cavity and said forward region exterior surface.

15. The bullet of claim 11 wherein each of said notches is radially oriented, such that a projection of said notch intersects the longitudinal axis.

16. The bullet of claim 11 wherein each of said notches is angled with respect to a radial orientation when viewed looking toward said leading face, such that a projection of said notch does not intersect the longitudinal axis.

17. The bullet of claim 11 wherein said groove is positioned closer to said leading face than to an end of said body trailing region, as measured along the longitudinal central axis.

18. The bullet of claim 17 wherein said groove is positioned closer to said leading face than to a midpoint between said leading face and the end of said body trailing region, as measured along the longitudinal central axis.

19. A bullet comprising: an elongated body having a body leading region, with a leading face and a leading region exterior surface, and having a body trailing region, said body being symmetrically disposed about a longitudinal central axis; a cavity formed in said body leading region, said cavity terminating at said leading face and extending therefrom towards said body trailing region; a plurality of longitudinal notches extending radially outward from said cavity, said notches dividing at least a portion of said body leading region into a plurality of petals separated from each other by said notches; and a groove in said leading region exterior surface and traversing each petal so as to divide said petal between a petal forward section, extending from said groove to said forward face, and a petal base section extending rearward from said groove, said groove intersecting said forward region exterior surface along a petal forward section rear edge on said petal forward section, said groove being configured to act as a living hinge that allows said petal forward section to bend relative to said petal base section under hydraulic forces, but which arrests such bending at a predetermined angle when such bending brings said petal forward section rear edge into contact with another surface of said groove, wherein said forward region exterior surface has a pressure-reducing section extending forward from said groove, said pressure-reducing section acting to reduce pressure in a region surrounding at least a portion of said petal forward sections that extend forward from said groove, and wherein said pressure-reducing section has a pressure section front diameter D.sub.F and a pressure section rear diameter D.sub.R where the pressure-reducing section terminates at the groove, with these diameters (D.sub.F, D.sub.R) selected such that D.sub.F>D.sub.R.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIGS. 1 and 2 are an isometric views illustrating a bullet prior to being fired into a target, with FIG. 2 being sectioned to show details of the interior. The bullet shown in FIGS. 1 and 2 has a conventional exterior profile, with the exception of an array of radially-extending slots, which separate a leading end region into a number of petals, and a groove which divides each petal between a petal forward section and a petal base section. The groove serves as a living hinge between the petal sections, allowing the petal forward section to bend up to a set angle with respect to the petal base section; the groove is further configured to arrest further bending beyond the desired degree, as illustrated in FIGS. 3A-3F.

(2) FIGS. 3A-3F show a series of partial section views illustrating the action of one of the petals of the bullet shown in FIGS. 1 and 2 when the bullet impacts a target and is subject to hydraulic forces. FIG. 3A shows the petal prior to impact. FIG. 3B shows the petal immediately after impact, when hydraulic forces acting on the petal forward section have caused it to start bending at an angle to the petal base section, with the groove acting as a living hinge. FIG. 3C shows the petal when the petal forward section has bent sufficiently to bring a petal forward section rear edge into abutment against a groove rear surface, blocking further bending action at the groove; at this position, the petal forward section acts as a ramp, creating additional outwardly-directed hydraulic forces as the bullet continues through the target. FIG. 3D shows the petal opening further as the bullet continues through the target. Since further bending at the groove is blocked, further spreading under hydraulic forces bends the petal base section outwards; these hydraulic forces are increased by the additional surface area of the petal forward section. FIGS. 3E and 3F show further bending of the petal base section as the bullet continues through the target, the outward spread of the petal base section significantly increasing the cross-section of the bullet and providing more effective transfer of kinetic energy to the target.

(3) FIG. 4 is an isometric view that illustrates a bullet that is similar to the bullet shown in FIGS. 1 and 2, but which employs a pressure-reducing section in the exterior profile of the petal forward sections extending forward from the groove; the pressure-reducing section of this embodiment is cylindrical, having a pressure section forward diameter and a pressure section rear diameter at the groove where the diameters are equal. This bullet also has a leading face that has a rearward-sloping portion to create a funnel leading into the cavity, further aiding in reliable spreading of the petal forward sections.

(4) FIG. 5 is an isometric view of a bullet similar to that shown in FIG. 4, but where the cylindrical pressure-reducing section is longer.

(5) FIG. 6 is an isometric view of another bullet having a cylindrical pressure-reducing section; however, in this embodiment the pressure-reducing section includes flared section where it intersects the groove.

(6) FIG. 7 is an isometric view of one example of a bullet that has a pressure-reducing section formed with a reverse taper, such that a pressure section forward diameter is greater than a pressure section rear diameter at the groove.

(7) FIG. 8 is a partial isometric view showing a portion of a bullet similar to that shown in FIG. 4, but having an alternative leading end region structure, where the petals are defined by notches that do not extend to the exterior surface so as to form complete slots.

(8) FIGS. 9, 10, and 11 are front views showing various configurations of slots that can be employed for bullets as disclosed herein. FIG. 9 illustrates a bullet such as shown in FIG. 4, where the notches that separate the petals extend radially outwards and intersect the longitudinal axis, while FIGS. 10 and 11 illustrate alternative bullets where the petals are separated by slots that do not extend radially straight outwards, but rather extend at an angle such that projections of the slots do not intersect a central longitudinal axis of the bullet.

(9) FIGS. 12-18 are partially sectioned views showing further possible configurations of bullets that could be employed, and which have pressure-reducing sections that reduce the inwards pressure compared to bullets having a conventional ogive profile.

DETAILED DESCRIPTION

(10) FIGS. 1-3F illustrate a bullet 100 that is generally formed as an elongated body having a body leading end region 102 that terminates at a leading face 104, and having a body trailing end region 106. The body 100 has a central longitudinal axis 108. A cavity 110 is formed in the leading end region 102, terminating at the leading face 104 and extending therefrom rearward towards the body trailing end region 106.

(11) The leading end region 102 has three longitudinal notches 112 that extend radially between the cavity 110 and a leading region exterior surface 114, such that the notches 112 divide the leading end region 102 into three petals 116. While three notches and petals are employed in this embodiment, it should be appreciated that a greater number of notches and petals may be employed depending on the overall configuration and/or composition of the bullet, in order to optimize results for particular chamberings and intended uses.

(12) The leading region exterior surface 114 is interrupted by a groove 118 that traverses each of the petals 116, and which divides each petal 116 between a petal forward section 120 and a petal base section 122. The petal forward section extends from the groove 118 to the leading face 104, and has a petal forward section rear edge 124 where the groove 118 intersects the leading region exterior surface 114. The petal forward section 120 has a petal forward inner surface 126, which defines a portion of the cavity 110. The petal base section 122 extends rearward from the groove 118 along the extent of the notches 112 and joins to the remainder of the body 100. The petal base section 122 again has a petal base inner surface 128, which defines a portion of the cavity 110. The groove 118 has a groove rear surface 130 that terminates at the leading region exterior surface 114.

(13) FIGS. 3A-3F illustrate the action of one of the petals 116 when the bullet impacts a target composed of a wet medium, such as ballistic gelatin or the body tissue of an animal. FIG. 3A illustrates the bullet 100 prior to impact (as in FIGS. 1 and 2), where the petal 116 has not yet been subjected to hydraulic forces.

(14) FIG. 3B shows the bullet 100 immediately after impact, when increasing pressure in the cavity 110 caused by hydraulic forces has exerted a radially-outward force on the petal 116. Because the groove 118 creates a region of reduced cross-section that acts as a living hinge, such forces initially cause the petal forward section 120 to bend outwards. This outward bending exposes the petal forward inner surface 126 to additional hydraulic forces as the bullet 100 moves through the target, resulting in further bending of the petal forward section 120. The bending of the petal forward section 120 continues until it has bent sufficiently to bring the petal forward section rear edge 124 into engagement with the groove rear surface 130, as shown in FIG. 3C. It should be noted that, depending on the overall profile of the bullet and the configuration of the groove, alternative surfaces may be brought into contact to close the groove and block further outward bending of the petal forward section.

(15) At the point shown in FIG. 3C, the engagement of the petal forward section rear edge 124 with the groove rear surface 130 blocks further bending action of the living hinge created by the groove 118. The petal forward inner surface 126 is inclined with respect to the longitudinal axis 108 by an angle . In preliminary testing, blocking further bending when the angle was about 30 was found to be effective for 0.300 Blackout bullets. When the petal forward inner surface 126 is blocked in its inclined position by closure of the groove 118, it acts as a ramp surface exposed to hydraulic forces; as the bullet 100 continues through the target, the forces on the petal forward inner surface 126 acts to apply outwardly-directed hydraulic forces on the entire petal 116, since these forces can no longer be accommodated by bending of the petal forward section 120 relative to the petal base section 122. FIGS. 3D-3F illustrate the outward bending of the petal base section 122 under the influence of the hydraulic forces as the bullet 100 continues through the target. The initial bending of the petal forward section 120 to an angled position at which it exerts increased outward forces to promote bending of the entire petal 116 allows the bullet 100 to achieve reliable expansion at subsonic velocities.

(16) Preliminary testing of bullets formed from solid copper with a configuration according to the bullet 100 shown in FIGS. 1-3F in 0.300 Blackout has found the performance of this configuration to be limited to velocities below about 900 fps (125 M/S). It is believed that hydraulic forces on the leading region exterior surface 114 create excessive inward forces on the petal forward sections 120 that impairs their ability to operate as intended at higher velocities.

(17) FIG. 4 illustrates a bullet that is designed to overcome the velocity limitations of the bullet 100 discussed above. The bullet 200 is again formed as an elongated body 200 with a body leading end region 202, terminating at a leading face 204, and a body trailing end region 206, and having a central longitudinal axis 208. A cavity 220 is again formed in the leading end region 202, and three notches 212 extend between the cavity 220 and a leading region exterior surface 214 to define three petals 216. Each petal 116 is divided by a groove 218 into a petal forward section 220 and a petal base section 222.

(18) In the bullet 200, the leading region exterior surface 214 does not follow a conventional bullet profile, but instead is formed with a pressure-reducing section 224 that extends forward from the groove 218. The pressure-reducing section 224 of this embodiment is cylindrical, having a pressure section front diameter D.sub.F, where the pressure-reducing section 224 joins a tapered section 226, that is equal to as pressure section rear diameter D.sub.R, where the pressure-reducing section 224 terminates at the groove 218. The tapered section 226, which may be ogive or frustoconical, extends forward from the pressure-reducing section 224 and terminates at the leading face 204.

(19) Because the leading region exterior surface 214 is parallel to the longitudinal axis 208 in the cylindrical pressure-reducing section 224, inwardly-directed hydraulic forces on the petal forward section 220 are greatly reduced. While the pressure-reducing section 224 illustrated is defined by outer surfaces that are parallel to the longitudinal axis 208, for some applications it may be practical to employ exterior configurations for the pressure-reducing section that are not cylindrical. Examples are sections that are nearly cylindrical, defined by surfaces that are within a small angle of being parallel to the longitudinal axis, or sections which form a reverse taper, sloping inwards towards the groove, such as shown in FIGS. 7 and 13-15.

(20) As a result of including the pressure-reducing section 224, the leading face 204 of the bullet 200 is significantly broader than the leading face 104 of the bullet 100. The leading face 204 of this embodiment is formed with a leading face outer region 228, which is planar and perpendicular to the longitudinal axis 208 and joins to the leading region exterior surface 214, and a rearward-sloping leading face inner region 230 which is inclined with respect to the longitudinal axis 208 and joins to the cavity 210. The leading face inner region 230 slopes toward the body trailing end region 206 as it progresses inward to the cavity 210, so as to form a funnel shape. When the bullet 200 moves through the target medium, force on the rearward-sloping leading face inner region 230 applies a radially outward force on the petal forward sections 220 to urge them outwards for more reliable spreading.

(21) In preliminary testing, 0.300 Blackout bullets of solid copper having a configuration according to FIG. 4, with the tapered section 226 being somewhat longer than the cylindrical section 224, were found to provide more reliable expansion at higher velocities compared to bullets such as shown in FIGS. 1-3F. These bullets were also found to remain intact at velocities up to about 1050 fps (320 m/s) when fired from barrels having a conventional twist rate of 1 in 8. However, some firearms having short barrels employ a faster twist rate, such as 1 in 5, and the forward sections of the petals of this bullet design were prone to breaking off when fired through barrels having such faster twist. It should be noted that, due to the more blunt overall profile provided by the pressure-reducing section and the resulting wider leading face, this bullet was not as reliable as desired in semi-automatic firearms when loaded into magazines intended for use with 5.5645 mm ammunition, rather than magazines designed specifically for use with 0.300 Blackout ammunition.

(22) FIG. 5 illustrates a bullet 250 that is similar to the bullet 200 shown in FIG. 4, but which has a cylindrical section 252 that is substantially longer than a tapered section 254 that terminates at a leading face 256. This results in the leading face 256 being significantly broader compared to the leading face 204. In preliminary testing, the bullet 250 with the elongated cylindrical section 252 was found to remain intact even when fired through barrels having a twist rate as fast as 1 in 5, while again having reliable spreading at velocities up to about 1050 fps (320 m/s).

(23) FIGS. 6 and 7 show further configurations that could be employed. Additional possible configurations are shown in FIGS. 12-18, discussed below. FIG. 6 illustrates a bullet 270 having a flared cylindrical profile for a pressure-reducing section 272. The pressure reducing section 272 has a constant diameter, equal to the pressure section front diameter D.sub.F, along most of its length, and then expands in a flare profile to a slightly enlarged pressure section rear diameter D.sub.R adjacent to a groove 274. FIG. 7 shows a bullet 290 having a pressure-reducing section 292 with a reverse taper, where a pressure section front diameter D.sub.F is greater than a pressure section rear diameter D.sub.R adjacent to a groove 294.

(24) While bullet configurations such as shown in FIGS. 1-5, formed from solid copper and employing three petals divided by directly radially-outward-extending notches, were found effective for 0.300 Blackout cartridges at the velocities and barrel twist rates indicated, it should be appreciated that details of the bullet configuration, construction, and composition may be altered to suit different uses. FIGS. 8-11 illustrate some possible variations in the formation of the notches that separate the petals. FIG. 8 illustrates a bullet 300 where three petals 302 are defined by notches 304 that do not extend to a leading region exterior surface 306, and thus do not form complete slots; this configuration may be preferable in some situations when more malleable materials than copper are employed.

(25) FIG. 9 is a front view of the bullet 200 shown in FIG. 4, illustrating that the notches 212 that separate the petals 216 extend straight radially outwards, and thus projections 232 of the notches 212 intersect the longitudinal axis 208. This results in a symmetrical profile for the petals 216. However, in some situations it may be preferred for the petals 216 to be asymmetrical, as discussed below.

(26) FIG. 10 illustrates a bullet 350 having petals 352 that are separated by notches 354 that do not extend radially straight outwards. Instead, the notches 354 extend at an angle such that projections 356 of the notches 354 do not intersect a central longitudinal axis 358 of the bullet 350. The angle of the notches 354 results in a non-symmetrical cross-section of the petals 352, altering their action after spreading as they are driven through the target by the rotational energy of the bullet 350. The angle as shown in FIG. 10 results in more sharply-angled leading side edges 360 of the petals 352 as they rotate through the target (as indicated by the arrow S, resulting from firing the bullet 350 through a barrel with right-hand twist rifling). In contrast, FIG. 11 shows a bullet 350 where the notches 354 are angled so as to form more blunt leading side edges 360. The use of more blunt leading side edges 360 may be particularly advantageous for bullets fired from a barrel having a fast twist rate, as such bullets have more rotational kinetic energy and the more blunt leading edges may aid in transferring the rotational kinetic energy of the bullet to the target.

(27) Additional possible bullet profiles are shown in FIGS. 12-18. FIG. 12 illustrates a bullet 400 having a pressure-reducing section 402 that has an ogive taper, but which is sharper than the taper of a conventional bullet such as the bullet 100 shown in FIGS. 1-3F, as indicated by the outline 404. Since the pressure-reducing section 402 still has a degree of tapering, it may still experience significant inwards forces, although reduced compared to the forces on the bullet 100. Preliminary testing suggests that, as the degree of pressure reduction increases, the speed at which the bullet will reliably expand also increases, and thus a bullet profile can be selected for a particular chambering, speed, bullet weight, and firearm type. With respect to the latter, the bullet configuration may be selected to suit a particular twist rate and/or a particular action (semi-automatic and fully-automatic firearms may have limits on the profile geometry that are needed to assure reliable feeding). The composition of the bullet may also affect the configuration that will be best suited for a particular use. In addition to varying the exterior profile, the profile of the cavity and/or the angle at which the groove closes to block further bending of the petal forward section may be adjusted to optimize performance for a particular use.

(28) FIGS. 13-15 illustrate bullets (450, 470, 490) that each have a pressure-reducing section (452, 472, 492) that is formed with a reverse taper, such that the diameter increases moving forward from a groove (454, 474, 494). These bullets (450, 470, 490) are also formed with a leading face inner region (456, 476, 496) that slopes rearward to form a funnel. The bullet 470 has a cylindrical region 478, while the bullet 490 has a frustoconical region 498.

(29) FIG. 16 illustrated a bullet 500 having a pressure-reducing section 502 formed with a reverse ogive profile. FIG. 17 illustrates a bullet 530 having a pressure-reducing section 532 with a straight cylindrical profile, while FIG. 18 illustrates a bullet 550 having a stepped-cylindrical profile of its pressure-reducing section 552, the pressure-reducing section 552 having a forward cylindrical section 554 with a larger diameter than a rear cylindrical section 556 that terminates at a groove 558.

(30) Additional variations in the overall shape and relative proportions of the bullet, the configuration and number of notches, profile of the cavity, exterior profile of the pressure-reducing section (when provided), location and configuration of the groove, etc. may be adjusted to suit particular bullet sizes, intended cartridge chamberings, and intended uses. Additionally, while testing to date has employed solid bullets formed from a single material, the use of composite construction, such as lead regions contained within a copper body, may be found optimal for some situations.

(31) While the novel features have been described in terms of particular embodiments and preferred applications, it should be appreciated by one skilled in the art that substitution of materials and modification of details can be made without departing from the spirit of the invention.