JP2007278631A - Manufacturing method of bullet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a bullet not including lead which can be used as a substitute for a lead bullet. <P>SOLUTION: A core 101 is inserted in an interior of a jacket 102 comprised of tube like (cylindrical) copper with a closed bottom. The jacket 102 housing the core 101 is inserted in a recessed part to be a mold for a bottom forging die 121 from the bottom, and the housed core 101 is pushed in by a punch 122 to form a shape of a bottom of the bullet. A punch 124 is pressed in a side of a head forging die 123, and the jacket 102 and the core 101 housed therein are pressed against the head forging die 123. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing bullets used for pistols, rifles, and the like.

  In general, bullets fired from rifles, shotguns and the like are made of bullets made of metal containing lead for the following reasons. First, by using lead having a large specific gravity (density), a bullet can be formed smaller and the position of the center of gravity can be easily controlled. Moreover, lead has advantages such as easy processing and easy formation of a desired shape having high flight performance.

  However, as is well known, the environmental impact of lead is regarded as a problem, and the diffusion of lead contained in fired bullets into the environment causes various problems. For example, a water bird such as a red-crowned crane that has been designated as a special natural monument has been reported to accidentally swallow a shot from the waterside of its habitat as a pebbles and die from lead poisoning. In addition, there are a number of accidents in which raptors such as Steller's sea eagle, designated as a natural monument, eat killed sika deer and die due to lead poisoning in the sika deer. Another problem is lead damage to soil and water resources caused by leaving the projectile bullets unattended.

  Due to the problem of lead described above, development of lead-free bullets that do not use lead is being promoted. For example, as rifle bullets, copper bullets, tin bullets, and dungsten polymer bullets in which a bullet core made of tungsten is coated with plastic have been developed. However, for example, copper bullets and tin bullets cannot obtain desired bullet characteristics as compared with lead bullets, and there is a problem that bullets using tungsten are very expensive.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a lead-free bullet that can be used as a substitute for a lead bullet at a lower cost.

  A bullet manufacturing method according to the present invention is a bullet manufacturing method for manufacturing a bullet in which a bullet core made of an alloy of tin and bismuth is covered with a metal shell made of copper, and one end is closed and the other end is A first step in which a cylindrical core made of tin and bismuth alloy is accommodated in an open cylindrical copper jacket, and the core accommodated in the jacket is pressed toward one end. The second step of pressing one end of the jacket against the first mold and forming one end of the bullet into the molded state, and pressing the formed one end in the direction of the other end, And a third step in which the head portion of the bullet is molded.

  In the bullet manufacturing method, the core is formed in a truncated cone shape, and in the first step, the core having the smaller diameter is disposed on the bottom side of the jacket so that the core is accommodated in the jacket. You may do it.

  As described above, according to the present invention, a cylindrical shape made of a bullet is formed by forging after a cylindrical shape made of a tin-bismuth alloy core is accommodated in a cylindrical copper jacket. Since it did it, the outstanding effect that the bullet which does not contain lead which can be used as an alternative of a lead bullet can be provided more cheaply is acquired.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing an example of a bullet manufacturing method according to an embodiment of the present invention. First, as shown in FIG. 1A, a core 101 made of an alloy of tin (Sn) and bismuth (Bi) and having a substantially truncated cone shape is prepared. The core 101 has, for example, a total length of 28 mm, a longer diameter of 6.6 mm, and a shorter diameter of 6 mm. Note that the end surface of the core 101 on the smaller diameter side (downward in FIG. 1) has a partial spherical shape. For example, the core 101 can be formed by casting using a mold as shown in the photograph of FIG.

  Next, as shown in FIG. 1B, the core 101 is inserted into a cylindrical (cylindrical) copper jacket 102 whose bottom (one end) is closed. For example, the jacket 102 has a total length of 31.7 mm, an outer diameter of 7.8 mm, and an inner diameter of 7 mm. At this time, the core 101 is accommodated so that the side of the truncated cone having the smaller diameter is the bottom side of the jacket 102.

  Next, as shown in FIG. 1 (c), the jacket 102 in which the core 101 is accommodated is inserted from the bottom into a recess that becomes the mold of the bottom forging die 121 and is accommodated in the punch 122. Push in the core 101. By this cold forging, the shape of the bottom of the bullet is formed as shown in FIG. Here, since the side with the small diameter of the truncated cone of the core 101 is the bottom side of the jacket 102, no gap or the like is formed between the jacket 102 and the core 101 in the forging, and the bottom of the bullet is not formed. The shape can be formed.

  Next, as shown in FIG. 1 (e), the jacket 102 is inserted into the hole serving as the die of the head forging die 123 from the opening (other end) side. At this time, the opening of the punch 124 is fitted to the bottom side of the jacket 102. Next, the punch 124 is pressed toward the head forging die 123 (direction), and the jacket 102 and the core 101 accommodated therein are pressed against the die portion of the head forging die 123. With this cold forging, as shown in FIG. 1 (f), a core 111 made of an alloy of Sn and Bi and a metal armor 112 covering the core 101, with the head narrowed down, A state in which a bullet composed of is manufactured is obtained. The bullet is molded to have a total length of about 34 mm, for example.

  Manufacturing in this way makes it possible to produce (manufacture) a bullet that is made of an Sn—Bi alloy and does not contain lead in a desired shape with high accuracy. Further, since a complicated manufacturing process is not used and an expensive material such as tungsten is not used, it is possible to manufacture a bullet containing no lead at a lower cost. In addition, according to the bullet produced by the manufacturing method shown in FIG. 1, as described below, it has the same landing characteristics as the lead bullet.

  First, experimental results are shown for the impact state (landing characteristics) of a bullet made of a bullet core 111 made of an Sn—Bi alloy with a Bi composition ratio of 57%. This impact test is performed by shooting a bullet into a block of gelatin. FIG. 3 is a photograph showing the state of gelatin (gelatin breaking behavior) broken by a shot bullet. A bullet is shot from above in FIG. FIG. 3 (a) shows gelatin destruction behavior by a bullet made of a bullet core 111 made of Sn—Bi alloy with a Bi composition ratio of 57%, FIG. 3 (b) shows gelatin destruction behavior by a lead bullet, FIG. 3C shows the gelatin breaking behavior by copper bullets. As shown in FIG. 3, the bullets of the Sn—Bi alloy produced by the manufacturing method described above show the same behavior as lead bullets. A Bi composition ratio of 57% is a eutectic composition of Sn and Bi.

  By the way, the bullet core 111 (core 101) should just be comprised from the alloy of Sn and Bi by which Bi was made into 50 to 80% (weight ratio). Hereinafter, the results of investigating the characteristics of the Sn—Bi alloy will be described. For example, as shown in FIG. 4, the Sn—Bi alloy is not easily cracked by bending if Bi is in the range of 30 to 80% (weight ratio). Further, as shown in FIG. 5, the Sn—Bi alloy has a hardness of less than 20.0 HV in a region where the composition ratio of Bi exceeds 50%. Further, as shown in FIG. 6, the Sn—Bi alloy has a high elongation when the Bi composition ratio is around 50%.

  As described above, since bullets are formed by cold forging, it is better that the Sn—Bi alloy does not easily crack when compressed, is not too hard, and is easier to stretch. On the other hand, the Sn—Bi alloy has a higher specific gravity as the Bi composition ratio increases. Since it is better for the bullet to have a higher specific gravity, the Bi composition ratio is desirably 80% at the maximum. If the composition ratio of Bi is Sn-Bi alloy at most 80%, it becomes possible to form bullets by pressure formation in a state where cracks are suppressed.

It is process drawing which shows the example of the manufacturing method of the bullet in embodiment of this invention. 4 is a photograph showing an example of a mold used to form the core 101. It is a photograph which shows the state (gelatin destruction behavior) of the gelatin destroyed by the shot bullet. It is a photograph which shows the result of the characteristic investigation (bending test) of Sn-Bi alloy. It is a characteristic view which shows the result of the characteristic investigation (hardness) of Sn-Bi alloy. It is a characteristic view which shows the result of the characteristic investigation (elongation rate) of Sn-Bi alloy.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Core, 102 ... Jacket, 111 ... Bullet core, 112 ... Metal armor, 121 ... Bottom forging die, 122 ... Punch, 123 ... Head forging die, 124 ... Punch.

Claims (2)

A bullet manufacturing method for manufacturing a bullet in which a bullet core made of an alloy of tin and bismuth is covered with a metal shell made of copper,
A first step in which a core made of an alloy of tin and bismuth formed into a cylindrical shape is housed in a cylindrical copper jacket having one end closed and the other end opened;
A second step of pressing the core housed in the jacket in the direction of the one end, pressing one end of the jacket against the first mold, and forming one end of the bullet;
And at least a third step of pressing the molded one end in the direction of the other end and pressing the other end of the jacket against the second mold so that the bullet head is molded. A method for producing a bullet characterized by the above. In the bullet manufacturing method according to claim 1,
The core is formed in a truncated cone shape, and the first step is such that the core having the smaller diameter is disposed on one end side of the jacket and the core is accommodated in the jacket. A bullet manufacturing method characterized by the above.