EP0689889A1 - Method for the production of a hunting bullet with hollow point - Google Patents

Abstract

Sporting shot is mfd. by powder metallurgy and is then calibrated. The powder includes a heavy element e.g. W as addn. to partic. Cu powder, to increase the overall density. A pyramid shaped punch is used to press the mixture in a press tool to form a hollow tip structure. After sintering, the product is calibrated in a press tool which is closed with a punch having the negative hollow shape of the tip. <IMAGE>

Description

Projectiles suitable for hunting should, if possible, achieve a committee, but at the same time give off enough energy in the target to prevent the game from jumping off. A projectile can only release energy through its cross-sectional area or its fragments. Bullets that do not change shape can only show a larger area in the firing direction by wobbling. Since this behavior cannot be easily controlled with different target resistances, it is excluded from the hunt.

Bullets are known from the prior art, the cross section of which increases in the target due to a so-called mushrooming. These include partial shell bullets with a shell made of a copper alloy or copper-nickel-plated mild steel and a core made of a lead alloy. So that a safe mushrooming is guaranteed even with low target resistances and low target speeds, this core must be made of very soft lead. The desired function - safe mushrooming and not completely disassembling the projectile in the target - is only possible in a narrow range of target speeds and target resistances that correspond to one another. With higher target resistances and / or higher target speeds, these projectiles often enlarge their cross-section too much and therefore there is a lack of penetration depth, especially in the case of stronger game. Occasionally, these bullets disintegrate completely into tiny fragments. To prevent this, some storeys have a two-part core structure. They have a core of soft lead at the front and a core of hard lead at the back. The soft, front core deforms in the target and the back core penetrates deeply or delivers the rejects desired by the hunter. Such bullets are very expensive to manufacture and therefore expensive. Another disadvantage of all lead core bullets is that they leave a part of their mass finely distributed in the game body. If the venison is not properly treated, this can lead to an undesirable, toxic lead intake when consumed.

To avoid this disadvantage, lead-free hunting bullets have been developed that have a solid body made of copper or a copper alloy. Since these materials are very hard compared to lead, hollow-point constructions must be provided so that such projectiles experience an increase in cross-section in the target by spreading their tips.

US Pat. No. 5,131,123 describes a method for producing a hollow bullet. At the beginning of this process, pieces of copper rod material are cut to length, which are annealed and then calibrated for length and diameter. These process steps are followed by the shaping of the hollow point in the projectile body. For this purpose, press punches are used in several successive stations, which are pressed into one of the end faces of the projectile body, the hollow tip being gradually formed deeper until its final depth and configuration is reached. This is followed by further process steps in which the projectile gets its final shape.

The disadvantage of this method is that a large number of steps are required to manufacture the projectile. In particular, the shaping of the hollow tip is very complex.

Furthermore, shell bullets are known from the military field, which have a sintered core made of tungsten. The sintering process is used here to make it easier to process the very hard and brittle tungsten material. The finished tungsten core has a very high hardness and a large specific weight with a relatively small diameter. This results in a very high cross-sectional load and therefore good armor plate penetration. Such bullets are unusable for hunting.

The object of the present invention is to provide a production method for a hunting bullet provided with a hollow point, which requires only a few work steps, the hollow point construction in particular being formed in only one work step.

This object is achieved in that the entire projectile is made by powder metallurgy from metal powder and then calibrated, the hollow point structure being introduced during powder pressing, which is formed into the final projectile tip during calibration.

Until the finished projectile is available, this process essentially requires only three work steps, namely pressing, sintering and calibration. The shaping of the hollow point construction, which is quite complex according to the prior art, takes place during the pressing, which is required anyway, so that this no separate work step is required.

In a further embodiment of the invention, in the matrix of the metal powder, for which copper powder is preferably used, at least one heavy element, such as. B. tungsten.

The bullets known from the prior art made of copper or of a copper alloy have the disadvantage of a low cross-sectional load, since these materials have a density of only 8.8 g / cm³ compared to a total density of about 10 g / cm³ when sheathed. Therefore, if you want to maintain their weight, these projectiles must be made longer. This results in a worsening of the external and target ballistic behavior, because the swirl stabilization is optimal only in a narrow range of projectile length and rotation speed. The method according to the invention has advantages here because

heavy elements, such as, into the copper matrix to increase the overall density B. tungsten, although this does not form an alloy with the base material. In this way, total storey densities can be achieved, which correspond approximately to those of conventional jacket storeys.

The method according to the invention also has advantages with regard to the density and thus strength profile in the projectile, which occurs in the projectile body during uniaxial pressing. It has been shown that a relatively hard projectile tail can be reached, which, as already stated in the prior art, has a positive effect on the depth of penetration and the scrap of the projectile.

Another advantage can be achieved by the method according to the invention if the inner wall of the press die before the pressing process with a sliding aid, in particular graphite or boron nitride, for. B. is provided by spraying. In addition to the fact that the powder slides better during pressing on the die wall, graphite or boron nitride particles are also deposited on the surface of the projectile or in the area near the surface, which reduces the friction between the barrel and the projectile during use.

Fig. 1.1

einen Pyramidenstempel zum Einbringen einer Hohlspitzkonstruktion während des Pressens eines Geschoßkörpers in Seitenansicht und Draufsicht,

Fig. 1.2

den Pyramidenstempel nach Fig. 1.1 um 90° gedreht,

Fig. 2.1

eine andere Ausführungsform eines Pyramidenstempels ebenfalls in Seitenansicht und Draufsicht,

Fig. 2.2

den Pyramidenstempel nach Fig. 2.1 um 90° gedreht und

Fig. 3

einen Schnitt durch einen Stempel zum Kalibrieren der Geschoßspitze sowie die dazugehörige Kalibriermatrize im Schnitt.

The invention is explained in more detail below using an exemplary embodiment. In the accompanying drawing:

Fig. 1.1

a pyramid stamp for introducing a hollow point construction during the pressing of a projectile body in side view and top view,

Fig. 1.2

1.1 the pyramid stamp according to Fig. 1.1 rotated by 90 °,

Fig. 2.1

another embodiment of a pyramid stamp also in side view and top view,

Fig. 2.2

the pyramid stamp according to Fig. 2.1 rotated by 90 ° and

Fig. 3

a section through a stamp for calibrating the projectile tip and the associated calibration matrix in section.

A heavy electrolyte copper powder with a maximum grain size of 200 µm and a dendritic grain shape is used as the base material for the projectile to be produced. Due to the grain size and the grain shape, high green strength and green densities can be achieved with this powder. 15% tungsten metal powder HC 1000 is mixed into this copper powder. The finished one Mixture is then metered into a pressing tool, which is closed from above with a pyramid stamp, as shown in FIGS. 1.1-2.2. The pressure is applied from below using a cylindrical lower punch. It is approximately 560 MPa. After compaction has been completed, the pyramid-shaped upper punch is raised and the green compact is pushed out with the lower punch facing up. After the green compact has been removed by a handling system, the lower punch is moved back to zero position in preparation for the next pressing process.

The hollow-point construction is shaped during the pressing process by means of the pyramid-shaped upper punch. The pyramid stamp with heel shown in FIGS. 2.1 and 2.2 has the advantage that the green compacts in the upper area are not so thin-walled and thus become much more stable. However, it is generally advisable to add about up to 1% by weight of pressing aids to the powder mixture, since this increases the strength of the thin-walled edges in the region of the pressed-in pyramid.

After pressing, the green compacts are sintered in batches in a protective gas furnace with a hydrogen atmosphere for about two hours. The sintering temperature is about 1000 ° C.

Since the projectile bodies vary somewhat in diameter over their length after the sintering process, they must be calibrated after the sintering. For this purpose, the sintered pieces are fed to a pressing tool, which is shown schematically in FIG. 3. Loading takes place from above. The pressing tool is then closed with an upper punch which has the negative contours of the projectile tip. The forming or calibration pressure of approximately 820 MPa is applied by a lower stamp, not shown. During the calibration process, the projectile tip is given its final shape by the upper punch, the pyramid-shaped depression previously introduced into the projectile body during pressing is squeezed. As is apparent from Fig. 3, the upper punch is equipped with a steel pin arranged in the center. During the calibration, the material of the projectile tip is pressed around this steel pin. In this way, the projectile receives a hollow point that is open to the front. After calibration, the finished projectile is ejected from the press tool.

To improve the target ballistic behavior, the projectile can still be soft annealed after calibration. This results in a bullet residual body larger in diameter in the target.

Claims (3)

Process for the manufacture of a hunting bullet with a hollow point, characterized in that the entire projectile is produced from metal powder by powder metallurgy and then calibrated, the hollow point construction being introduced during the powder pressing, which construction is formed into the final projectile tip during calibration. A method according to claim 1, characterized in that to increase the overall density of the projectile at least one heavy element, such as. B. tungsten, the metal powder, especially copper powder, is admixed. Method according to claim 1 or 2, characterized in that the inner wall of the pressing die is provided with a sliding aid, in particular graphite or boron nitride, before the pressing process.

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