Patent Application
20110056404
This invention relates generally to bullets, and more particularly to small caliber bullets having a metal jacket and a hollow point.
Bullets are jacketed to improve the ability of the bullet to penetrate barriers and remain intact. Most commonly the jacket (typically copper) is plated onto the core (typically lead). This results in a thin, uniform jacket that provides more structural integrity to the bullet and improves penetration in at least some circumstances.
Another type of jacketed bullet is made by forming a cup-shaped jacket perform (typically copper) and inserting a preformed core (typically lead) into the jacket perform, bonding the core to the jacket, and forming the open front end of the jacket into the front end of the bullet, so that the thickness of the jacket increases toward the back of the bullet.
Another type of jacketed bullet is made by forming a cup-shaped jacket preform (typically copper) and inserting a preformed core (typically lead) into the jacket preform and swaging the core and jacket together, and forming the closed end of the bullet into the front of the bullet. This type of jacketed bullet is more completely described in co-assigned U.S. Pat. No. 5,208,424, the entire disclosure of which is incorporated by reference. While the thickness of the jacket of this bullet tapers toward the rear, the core is merely mechanically held in the jacket.
One measure of bullet performance is the Federal Bureau of Investigation Ammunition Test Protocol. This Protocol is a series of tests that measure a bullet's ability to defeat different types of barriers, penetrate the target, and retain mass and expand to cause maximum damage to the target. The Protocol assesses a bullet's ability to inflict effective wounds after defeating various intervening obstacles commonly present in law enforcement shootings. The overall results of a test are thus indicative of that specific cartridge's suitability for the wide range of conditions in which law enforcement officers engage in shootings.
According to the FBI Ammunition Test Protocol, bullets are fired into 6×6×16 inch blocks of 10% Ballistic Gelatin (Kind & Knox 250-A) at 4° C. (39.2° F.) five times in eight separate events. Each shot's penetration is measured to the nearest 0.25 inch. The bullet is recovered, weighed, and measured for expansion by averaging its greatest diameter with its smallest diameter. The test events are:
Test Event 1: Bare Gelatin The gelatin block is bare, and shot at a range of ten feet measured from the muzzle to the front of the block.
Test Event 2: Heavy Clothing The gelatin block is covered with four layers of clothing: one layer of cotton T-shirt material (48 threads per inch); one layer of cotton shirt material (80 threads per inch); a one layer of Malden Mills Polartec 200 fleece; and one layer of 14.4. ounces per yard cotton denim (50 threads per inch). The block is shot at ten feet, measured from the muzzle to the front of the block.
Test Event 3: Steel Two pieces of 20 gauge, hot rolled steel with a galvanized finish are set three inches apart. The gelatin block is covered with Light Clothing and placed 18 inches behind the rear most piece of steel. The shot is made at a distance of 10 feet measured from the muzzle to the front of the first piece of steel. Light Clothing is one layer of the above described T-shirt material and one layer of the above described cotton shirt material.
Test Event 4: Wallboard Two pieces of half-inch standard gypsum board are set 3.5 inches apart. The pieces are six inches square. The gelatin block is covered with Light Clothing (as described in Test Event 3) and placed 18 inches behind the rear most piece of gypsum. The shot is made at a distance of ten feet, measured from the muzzle to the front of the first piece of gypsum.
Test Event 5: Plywood One piece of three-quarter inch AA fir plywood is used. The piece is six inches square. The gelatin block is covered with Light Clothing (as described in Test Event 3) and placed 18 inches behind the rear surface of the plywood. The shot is made at a distance of ten feet, measured from the muzzle to the front surface of the plywood.
Test Event 6: Automobile Glass One piece of A.S.I. one-quarter inch laminated automobile safety glass measuring 15×18 inches is set at an angle of 45° to the horizontal. The line of bore of the weapon is offset 15° to the side, resulting in a compound angle of impact for the bullet upon the glass. The gelatin block is covered with Light Clothing (as described in Test Event 3) and placed 18 inches behind the glass. The shot is made at a distance of ten feet, measured from the muzzle to the center of the glass pane.
Test Event 7: Heavy Clothing at 20 yards. This event repeats Test Event 2 but at a range of 20 yards, measured from the muzzle to the front of the gelatin.
Test Event 8: Automobile Glass at 20 yards. This event repeats Test Event 6 but at a range of 20 yards, measured from the muzzle to the front of the glass, and without the 15° offset.
A composite score of the 40 shots is then established, with the maximum score being 500. A higher score generally indicates a more consistent performing bullet under wide ranging conditions. The parameter that has the highest impact on overall score is the standard deviation of penetration amongst all 40 shots. If even a single shot fails to upset, it will subsequently over penetrate and increase the measured standard deviation thus resulting in a lower score. Existing jacketed bullets generally perform satisfactorily on the FBI Ammunition Test Protocol, with scores ranging from 275 to 375 for plated jacketed bullets, and from 200 to 325 for bullets made with jacket preforms. While functional, there was clearly room for improvement, at least as measured by the FBI Ammunition Test Protocol.
This invention relates generally to improvements in small caliber bullets having a metal jacket and a hollow point. According to one embodiment, the jacketed bullet comprises a dense core of a first material substantially surrounded by and bonded to a jacket of a second material. The thickness of the jacket varies, preferably decreasing from the front end of the bullet toward the back end of the bullet.
In one preferred embodiment the bullet has an aft section with a generally cylindrical sidewall, a forward section with a tapering sidewall generally tapering toward the front end of the bullet, and a recess in the front end. The jacket is preferably thicker at the front end of the bullet than at the back end of the bullet. More preferably, the thickness of the jacket decreases from the juncture between the aft and forward sections, toward the back end of the bullet. The jacket may extend at least partly into the recess in the front of the bullet. Some embodiments of the bullets may include a plurality of longitudinally extending lines of weakness in the forward section of the bullet to facilitate the formation of petals after the bullet strikes an object. The lines of weakness can be linear areas of reduced thickness in the jacket, or slits through the jacket. These lines of weakness are preferably substantially equally spaced around the circumference of the bullet so that the bullet forms petals of substantially equal size upon expansion after impact.
Some embodiments of the bullets have an opening in the back, exposing the core. While in other embodiments this opening is closed, for example with an insert between the jacket and the core, covering the opening.
In the various embodiments the core is more than swaged or mechanically molded to the jacket with pressure, and is bonded to the jacket. The preferred bonding process is soldering in which a preformed core is inserted into the jacket and heated so that the core bonds to the jacket. Flux can be introduced into the jacket to facilitate bonding of the core to the jacket. Other methods of bonding can also be used, including for example the use of adhesives.
The various embodiments of the present invention provide a jacketed bullet in which the core is bonded to the jacket and the thickness of the jacket varies. This general configuration allows the bullets to be designed to defeat many different types of barriers, and to provide good and consistent penetration. These and other features and advantages will be in part apparent and in part pointed out hereinafter.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. Generally, prior art jacketed bullets either had a thin, uniform plated jacket (as shown generally in
A preferred embodiment of a bullet constructed according to the principles of the present invention is indicated generally as 20 in
The core 22 is preferably made of a dense, malleable material, such as lead or a lead alloy. The core 22 could also be made of a non-lead metal, such as bismuth, bismuth alloys, tungsten, tungsten alloys, tin or tin alloys, or any other dense, malleable, metal that can be bonded to the jacket. The jacket 24 is preferably made from a stronger material, such as copper, a copper alloy, or steel, or any other suitable metal. The core 22 and the jacket 24 can be bonded by melting or soldering. As described in more detail below, according to the preferred method of making the bullet, a preformed core in placed in a preformed jacket, and the core and jacket are heated form a metallurgical bond between the jacket and the core, preferably to a temperature high enough to completely convert the core material to a molten state, (about 700° F. in this preferred embodiment in which the core is made of lead or lead alloy). Flux can be used to facilitate bonding. Alternatively, an adhesive could be used to bond the core 22 and the jacket 24. Examples of suitable adhesives include epoxy, glue, or any other type of contact adhesive. Other methods of bonding the core and the jacket can also be used provided that they achieve a true bond between the material of the jacket and the material of the core, and not just a mechanical connection.
The jacket 24 is not of uniform thickness, and is preferably thicker adjacent the front end 30 of the bullet than adjacent the back end 36. In the preferred embodiment, the jacket 24 is between about 0.018 and about 0.030 inches thick adjacent the front end 30 of the bullet, and between about 0.006 and about 0.020 inches thick adjacent the back end 36 of the back end of the bullet. The greater thickness of the jacket 24 adjacent the front end 30 of the bullet, combined with the bonding of the core and the jacket allows the front end of the bullet to resist crushing while penetrating deeper. The lesser thickness of the jacket 24 adjacent the rear of the bullet allows the cylindrical portion of the bullet to further engage the rifling of the barrel resulting in improved accuracy over thicker jacket bullets. The jacket 24 can be open at the back end 36 of the bullet, exposing the core. Alternatively, the core can be completely enclosed. A disk-shaped insert 38 can be positioned over the core, and the jacket crimped around the insert to enclose the core. The jacket 24 preferably extends at least partly into the recess 32 in the front 30 of the bullet 20, and preferably extends only partly into the recess. The thickness of the jacket in the recess generally decreases from the front 30 of the bullet to the edge 38 of the jacket.
There are preferably a plurality of longitudinally extending lines of weakness 40 in the forward section 28 of the bullet 20 to facilitate the formation of petals after the bullet expands upon striking an object. These lines of weakness 40 preferably comprise linear area of reduced thickness in the jacket or slits extending through the jacket and possibly at least partially into the core. These lines of weakness are preferably substantially equally spaced around the circumference of the bullet so that the bullet forms petals of substantially equal size upon expansion. However the lines of weakness could be placed so that the petals are not equal in size. In certain applications unequal petal size could be advantageous. In the preferred embodiment there are six lines of weakness 40, which form six petals, but there could be fewer or more lines of weakness if desired.
In accordance with another aspect of this invention, a method of making bullets having a metal jacket with a hollow point is provided. Generally, the method comprises forming a bonded core 22 inside a preformed cup-shaped jacket 24 having with a first closed end 42 and a sidewall 44 whose thickness generally decreases from the first closed end toward a second open end 46. An opening 48 is formed through the first closed end 42 of the jacket 24 and into the core 22. Lines of weakness 40 in the jacket 24 adjacent the opening 48 formed in the first closed end. The first closed end is formed into an ogival profile to form a tapered forward section 28 and front end 26 of the bullet, with the recess 32 therein.
The back end 36 of the bullet 20 can be formed by wrapping the jacket adjacent the open end over the core, leaving an opening in the jacket through which the core is exposed. Alternatively the jacket can be closed by inserting a disk 38 into the open end of the jacket, and wrapping the jacket adjacent the open end over the disk, forming a closure which covers the core 22.
The step of forming the bonded core inside the cup-shaped jacket can comprise inserting a preformed core 22 into a preformed cup shaped jacket preform 24, and heating the core and jacket preform to form a bond between the core and jacket. Flux can be inserted into the jacket or applied to the core before heating the jacket and the core, to facilitate bonding. Alternatively, the step of forming the bonded core inside the cup-shaped jacket preform can comprise inserting a preformed core into a preformed jacket, and adhesively bonding the jacket and the core. In still another alternative, the step of forming the bonded core comprises introducing molten core material into the jacket and allowing the core material to cool under conditions that cause the core to bond with the jacket.
The step of forming the opening through the first closed end of the jacket and into the bonded core and the lines of weakness in the jacket adjacent the opening can comprise punching the first closed end of the jacket to simultaneously form the recess and the lines of weakness.
The step of forming the first closed end into an ogival profile comprises forcing the jacket and core into a die. The back end 38 of the bullet can be formed at the same time, either forming the jacket around the core to form an open back end, or inserting a disk-shaped insert into the open end of the jacket and forming the jacket around the core and insert to form a closed back end.
A comparison between one embodiment of a bullet constructed in accordance with the principles of this invention, and embodiments of two prior art bullets is shown in Table 1. Bullet 1 in the testing shown in the Table is a Winchester 40 S&W 165 gr T-series—Reverse Tapered Jacket, in which the core is not chemically bonded to the jacket. Bullet 2 in the testing shown in the Table is a Winchester 40 S&W 165 gr Bonded JHP in which the core is bonded in a conventional jacket, i.e. a plated bullet. Bullet 3 is an embodiment of a bullet constructed according to the principles of this invention, with a core that is chemically bonded in a reverse taper jacket. While Bullets 1 and 2 in the tests had good scores under the FBI protocol, Bullet 3 was surprisingly superior to the prior art bullets 1 and 2, earning in the testing a composite score of 374.5 nearly 100 points above Bullet 1 and nearly 170 above Bullet 2.
The invention is not limited to the above-described embodiments. Various modifications and variations may be made within the spirit and scope of the invention. Although only some embodiments of the invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/034,149, filed Mar. 5, 2008, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61034149 | Mar 2008 | US |
