EP1728044B1 - Delayed expansion hunting bullet - Google Patents

Abstract

The invention relates to ammunitions for hunting weapons. The inventive ammunition consists of a bullet which has the same calibre as the weapon or is undercalibrated and comprises a bullet body (2) provided with an ogival head (4) and carrying a fin and an internal carried arrow (3) inserted into an axial hole (8). Said internal arrow (3) is protruded with respect to the front face (10) of the bullet body, is slidable on impact against a target and penetrates into an open conical cavity (11) formed in the front face (10) of the ogival head (4). Said invention can be used for small, medium and large calibre munitions, in particular for big game animals.

Description

The present invention relates to ammunition for small arms, medium and large calibres, and more particularly advanced bullet bullet ammunition, particularly for hunting weapons, having improved efficiency, by a delayed expansion on target.

Bullet ammunition has been known in the art for many years. They comprise a subprojectile, or arrow, stabilized by empennage, associated with a shoe, or launcher, the caliber of the weapon, so that the launcher surrounds at least partially the arrow, the arrow-launcher assembly being placed in a crimped cartridge, which further comprises a primed sleeve and a propellant charge. Ammunition of this type is described for example in the patent FR-A-2555728 .

In the field of hunting weapons, during the impact of ammunition of the arrow bullet type on the target, the arrow is deformed, and it is desirable that this deformation be controlled and does not provide too much dislocation of the arrow in several small fragments that could be dangerous.

The patent FR-A-2795170 describes ammunition that meets this objective, and essentially consists of a bullet of the caliber of the weapon or under-calibrated, comprising a profiled front portion, a central portion, and a rear portion that can carry an empenne, and comprising, arranged along its axis, an internal arrow carried, of rigidity at least equal to that of the body of the ball. The balls of this type are very precise and have the advantage of maintaining their mass during the impact on the target. According to this technique, the diameter of the nose of the warhead is between 40 and 50% of the maximum diameter of the bullet, which gives it a significant aerodynamic drag. These bullets are therefore mainly intended for so-called "beat" firing, at short and medium distances, less than 150 m for rifles, and of the order of 50 to 60 m for shotguns.

Conventional lead-core bullets are mainly used on low-resistance targets and are ineffective on medium or high-strength targets.

So-called expansive bullets are also known, which have the characteristic of being deformed on impact by a mushroom-shaped expansion, including on medium-strength targets. For example, the patent US Patent 4,685,397 describes a bullet with an ogival body whose head comprises a blind hole closed by an insert capable of sinking into the hole during impact, and to push outwardly the wall of the nose. The patent EP-A-918208 discloses another embodiment of such a cylindrical body bullet and ogival head having a blind hole along its axis, closed by an insert, supplemented by a peripheral annular groove. Thus, on impact, the insert sinks into the blind hole and then causes deformation by expansion of the ogival head, which is facilitated by the annular groove. Requirement PCT WO 03.093758 discloses a partial expansion and fragmentation ball having an orifice located in the head of the warhead, completely closed by a plug mounted on a rod, the movement of which causes deformation of the body of the bullet. Requirement WO 0120245 describes another example of bullet whose ogival head has a hole closed by an insert. Another example of a monobloc expansive ball is described in the patent application WO 97.40334 .

A variant of a delayed-expansion hunting bullet is described in the patent EP-A-1394498 according to which the bullet body is completely traversed by an element which, on impact, causes deformation of the bullet body.

However, expansive ammunition of this type has the disadvantage of an early expansion of the impact on the target, which is not always desirable, and a random control of the deformation according to the conditions of the shooting, accompanied by a risk of fragmentation of the ogival head of the bullet.

Thus, there is still today a need to be able to dispose of ammunition, especially for hunting weapons, having a controlled expansion on impact, ensuring an effective release of their energy.

The present invention relates to bullet-type ammunition providing excellent target efficiency, and more particularly relates to ammunition for hunting weapons capable of preventing the formation of multiple fragments and ensuring the destruction of the hard parts of said target, delaying expansion to release energy into the most vulnerable part of the target, especially on hard targets and strong resistance.

The subject of the present invention is therefore a small, medium or large caliber ammunition ammunition of the type with an internal deflected boom, providing a controlled expansion upon impact on the target.

The invention also relates to a hunting weapon ammunition, as mentioned above, providing a delayed expansion upon impact on the target, in particular on a hard-shelled and hard-shelled target, without decreasing the efficiency on low and medium resistance targets.

The subject of the invention is also an ammunition for hunting weapons with improved terminal efficiency on a hard and resistant target, in particular for big game, constituted by a cartridge, consisting of a primed sleeve, a charge of propellant powder, and a complete ball including an internal arrow carried, if any associated with a launcher caliber of the weapon.

The invention finally relates to a lead-free ammunition for hunting weapons having an optimized terminal ballistics, providing an almost total release of energy in the soft parts of the target after perforation of the hard part, avoiding any fragmentation of the bullet on impact.

The ammunition for small arms, medium and large calibres, according to the present invention is constituted by a bullet of the caliber of the weapon or under-calibrated, of the type comprising a bullet body comprising an ogival head and able to carry a stamina, and an internal deflected spear inserted in an axial hole, the rigidity of the spire being greater than or equal to that of the body of the ball, and it is distinguished in that the inner spire is arranged protruding from the face before the bullet body, can slide at impact on the target, and passes through an open conical cavity formed in the front face of the ogival head.

According to a preferred embodiment, it is advantageous to combine this conical cavity with an expansion lip formed at the junction of the conical cavity and the end face of the ogival head. It is advantageous that this open conical cavity has a shape such that the angle of its generatrix with the axis of the arrow is between 10 and 50 °. According to a characteristic of the invention, the section of the internal arrow is less than or equal, over its entire length, to the diameter of the axial hole. Thus, the sliding of the internal arrow does not directly cause any deformation of the bullet body.

The axial hole in which the internal arrow is inserted is preferably a blind hole, of depth generally between 30 and 80% of the height of the bullet body.

The sliding of the internal arrow, which causes the effect of delayed expansion at impact, is obtained by providing a suitable space between the base of the internal arrow and the bottom of the axial hole in which it is inserted, this corresponding space. at a free distance along the axis which is greater than or equal to the sliding distance of the internal arrow. This distance is set according to the desired effect and the conditions for shooting. It is preferably at least equal to the length of the arrow projecting from the front face of the body of the ball. According to a preferred embodiment of the invention, this free distance, available for the sliding of the boom, is between 0.2 and 1.5 times the total length of the internal boom. In the case of ammunition for hunting weapons, the internal arrow protrudes from the frontal face of the head ogival ball on a length generally between 2 and 7 mm.

During the impact, the head of the internal arrow first hits the target and then slid into the body of the bullet at the same time as it enters the target. In this first phase, the hydrodynamic pressure generated by the penetration of the head of the internal arrow in the target is practiced practically only on the front face of the internal boom, then, when the latter sinks into the body of the ball, the distance of protrusion of the internal arrow decreases, until the hydrodynamic pressure is also exerted on the front face of the head of the ball.

In a second phase, the open conical cavity formed on the ogival head and the expansion lip combine their effects to initiate the deformation by expansion of the ogival head and amplify it at the same time as the bullet enters the target, thereby creating a large hydrodynamic cavity in the most vulnerable part of the target.

During this expansion movement of the ogival head, then the bullet body, the internal arrow slides and moves back to abut against the bottom of the axial hole. When the expansion movement continues, the front face of the internal arrow emerges from the bullet body, allowing the destruction, if any, of the hard parts of the target that may be in the path.

According to one embodiment, the internal arrow is constituted by at least two consecutive elements arranged contiguously on the same axis. According to a variant according to the present invention, it consists of at least two consecutive elements arranged on the same axis and separated by a gap.

It is advantageous, according to the invention, to provide in the munition a recoil limiter of the internal boom. This limiter may be constituted by a decrease in the diameter of the rear portion of the hole receiving the arrow, thus forming a shoulder against which the internal arrow abuts when it slides during the impact on the target. According to a variant, it is constituted by a second arrow placed at the bottom of the hole receiving the two arrows. In this configuration, the internal sliding arrow can detach after deformation of the bullet body by expansion in the target, and the second arrow can destroy the resistant elements possibly present in the target.

According to an advantageous variant embodiment of the invention, particularly in the case of shots on medium-strength targets, the inner boom has frustoconical ends. The frustoconical shape of the front end facilitates the beginning of the expansion movement of the ogival head. This frustoconical shape cooperates with the open frustoconical cavity surrounding the internal deflection and makes it possible to reduce the hydrodynamic pressure created during the penetration of the arrow into the target and thus to reduce the length of the hydrodynamic channel formed. Preferably, the front and rear ends of the boom have the same frustoconical shape, which simplifies the manufacture of the ammunition. As can be seen, the hunting bullet of the invention is clearly distinguishable from expansion bullets such as those described in the patents EP-A-918208 and US Patent 4,685,397 where the insert serves to close the axial cavity made in the head of the warhead and deform it by simple displacement on impact, while the internal boom used in the invention is designed to cause a delayed expansion and does not directly cause deformation of the ogival head of the bullet body.

The internal arrow may be made of a single element or of several consecutive elements arranged on the same axis, contiguously or separately. It may be advantageous, for example, to provide an internal arrow in two elements. According to an alternative embodiment, the internal deflection may be of the controlled fragmentation type and may comprise elements that disperse on impact, for example balls of diameter substantially equal to that of the internal deflection. This embodiment makes it possible to obtain splinters calibrated during the impact, and thus improve the lethal power of ammunition by creating secondary injuries.

The internal boom can be made for example of steel, titanium, copper, brass or aluminum alloy with high mechanical strength, or technical plastic such as ABS, very high rigidity.

The body of the bullet may be for example copper, or brass containing 5 to 40% zinc and 95 to 60% copper, or metal alloy having the desired mechanical properties, for example aluminum alloy or aluminum. composite material based on tungsten or bismuth. Compared with conventional techniques, the technique of the invention has the advantage of allowing the lead to be completely or partially replaced by another metal or alloy known to be non-polluting. In the case of a stabilized bale stabilized, the empennage may be metal or polymer formed by plastics directly on the metal body of the sub-projectile.

The internal arrow and the bullet body used in the munitions of the invention may be made of the same material, for example copper or brass. In this case, the rigidity of the internal arrow is equal to that of the body of the ball. According to a preferred embodiment, the internal arrow is made of a material of greater rigidity than the bullet body, and the ammunition is then of the bimetallic or monometallic type with differentiated rigidity between the bullet body and the arrow.

The internal arrow is generally in the form of a rod of revolution with a constant section, coaxial with the projectile. It may be advantageous to provide ribs on the cylindrical surface to improve the attachment of the internal arrow in the body of the ball. They may be annular or helical ribs, or, preferably, longitudinal ribs, 2 to 6 in a part or the entire length of the cylinder, symmetrically with respect to the axis. In addition, the longitudinal ribs can be used to form fracture primers on the front face of the bale when the boom is placed. internal cylindrical force introduction into the hole previously drilled along the axis of the ball. If the bale is obtained by cold deformation, the internal deflected boom, previously placed in the axis of the bale blank, will print its longitudinal ribs in the material of the discharged body by means of a press and will thus create the primers desired breaks.

These breaking primers, cooperating with the internal deflection, promote the deformation of the head of the bullet during the impact by "petalization" or "muscular" in as many elements as ribs, around the central internal arrow which retains its general shape and serves as a structure ensuring the cohesion of the whole. They can be associated in combination with circular or longitudinal grooves made around the bead, preferably in the zone deforming by expansion, whose deformation must be controlled.

As indicated above, the ball may be of the gyroscopic stabilization or empennage type. The gyrostabilized bullet is used in a rifled barrel, so that the scratch of the barrel, cooperating with a tenon integral with the bullet, gives it a rotational movement along its axis. Stabilized bullets can be used in smooth-bore weapons.

The ammunition according to the present invention can be used on very hard and very strong targets, on which they provide excellent terminal efficiency, without diminishing their effectiveness on low or medium resistance targets. This excellent efficiency results in particular from the effect of delayed expansion at impact, after perforation of the hard and resistant parts of the target by the internal arrow. It is obtained while maintaining the aerodynamic parameters of the approach bales with an internal arrow carried using the technique described in the patent FR-A-2795170 aforementioned, even at significant distances, of the order of 300 m and more. The point of impact is then identical to that of approach bales at internal arrows range above thanks to the aerodynamic parameters and the construction of the ball in flight order.

In addition, the delayed expansion is provided from all angles of fire on the target, including tangential angles through the open cavity of the forward portion of the bullet, combined with the relatively small diameter of the inner boom.

The ammunition of the invention is therefore particularly suitable for hunting large game with thick skin or shell hard and resistant, for example some large African game, especially the buffalo.

• Fig. 1 : une vue schématique en coupe partielle d'une balle à flèche interne suivant l'invention.
• Fig. 2 : une demi-coupe transversale de la balle à flèche interne de la Fig. 1, en position de début d'impact sur cible.
• Fig. 3 : une vue schématique de la forme de l'empreinte obtenue sur une cible de référence avec une balle suivant l'invention.
• Fig. 4 : une vue schématique de la forme de l'empreinte obtenue sur une cible de référence avec une balle à flèche interne de type connu.
• Fig. 5 : une demi-vue simplifiée en coupe d'une balle sous-calibrée à flèche interne portée suivant l'invention, pour fusil de chasse.
• Fig. 6 : une demi-vue schématique en coupe d'une variante de l'invention, comportant un limiteur de recul de la flèche interne au moyen d'une diminution du diamètre du trou recevant la flèche.
• Fig. 7 : une demi-vue schématique en coupe d'une autre variante de l'invention, comportant un limiteur de recul de la flèche interne au moyen d'une deuxième flèche.
• Fig. 8 : une demi-vue simplifiée en coupe partielle d'une variante de la balle de la Fig. 1, comportant une flèche interne à tête tronconique.

The characteristics and advantages of the invention will appear in more detail in the following description relating to nonlimiting examples, with reference to the appended drawings which represent:

• Fig. 1 : a schematic partial sectional view of an internal arrow bullet according to the invention.
• Fig. 2 : a half-cross section of the ball with an internal arrow of the Fig. 1 , in the target impact start position.
• Fig. 3 : a schematic view of the shape of the impression obtained on a reference target with a bullet according to the invention.
• Fig. 4 : a schematic view of the shape of the impression obtained on a reference target with an internal arrow bullet of known type.
• Fig. 5 : A simplified half-view in section of a sub-calibrated bullet with internal arrow scope according to the invention, for shotgun.
• Fig. 6 : A schematic half-sectional view of a variant of the invention, comprising a recoil limiter of the internal boom by means of a decrease in the diameter of the hole receiving the arrow.
• Fig. 7 : A schematic half-sectional view of another variant of the invention, comprising a recoil limiter of the internal boom by means of a second arrow.
• Fig. 8 : a simplified half-view in partial section of a variant of the ball of the Fig. 1 , comprising an internal arrow with frustoconical head.

As shown in Fig. 1 , the caliber ball (1) comprises a bullet body (2) and an internal arrow (3). The ball body (2) is monobloc and comprises at its front part an ogival head (4), at its central part a bullet body (5) and at its rear part a narrowing of the base (6).

Longitudinal ribs (7) are formed on the surface of the internal arrow (3) which is placed in a hole (8) drilled in the axis of the central part (5) and opening on the front of the ogival head ( 4). The whole of the bullet and the internal arrow is partially introduced into a case carrying a primer and a propellant charge, of conventional type, not shown.

During manufacture, the internal arrow (3), preferably made of steel, is forcefully inserted into the hole (8) so that its front face (9) protrudes with respect to the front face (10) of the warhead (4). The depth of the hole (8) is significantly greater than the length of the internal arrow (3) inserted therein. Thus, a force applied on the front face (9) of the internal arrow (3) causes the sliding of the latter in the hole (8) to the bottom of the hole.

The front face (10) of the ogival head (4) of the bullet body (2) made of brass, has an open conical cavity (11) forming with the bend of the warhead (4) an expansion lip (12). ) facilitating the control of the expansion of the head (4) during the impact on the target. The opening of the cone (11) is such that the angle of the generator with the axis of the arrow is about 30 °. The central part (5) of the bale body (2) carries on its outer wall a crimping groove (13) for insertion into the cartridge, as well as separate decompression grooves of the propellant gases (14, 14 '). by friction belts (15). These decompression grooves facilitate the passage of the ball into the barrel of the weapon after firing the load. The precise dimensions of the necking (6) at the back of the bullet body are determined by the overall aerodynamic study of the ball, according to the known techniques.

The Figure 2 shows the position of the ball in contact with the target (16) before penetration into it.

At the impact on the target (16), the head of the internal arrow (3) first hits the target and then slid into the hole (8) at the same time as the bullet enters the target. drilling a channel around the ogival head (4), by hydrodynamic effect, before any deformation of the head (4) itself.

In this first phase, the hydrodynamic pressure is exerted practically only on the front face (9) of the inner boom (3). When the latter sinks into the hole (8) the distance x separating the front face (9) of the internal arrow (3) of the front face (10) of the ogival head (4) decreases until the Hydrodynamic pressure is also exerted on the front face (10) of the ogival head (4).

Thanks to the open conical cavity (11) on the ogival head (4) and the expansion lip (12), the expansion deformation of the ogival head (4) starts in a second phase and increases in size. At the same time the bullet enters the target, creating a large hydrodynamic cavity in its movement in the most vulnerable part of the target.

During this expansion movement of the ogival head (4), then of the central portion (5) of the bullet body (2), the internal deflected boom (3) moves back to abut against the bottom of the hole (8). When the expansion movement continues, the inner end face (8) is then found again and emerges from the bullet body (2), allowing the destruction, if any, of the hard parts of the target can find on the trajectory.

In the terminal phase of the expansion movement of the bullet body (2), the internal arrow (3) may eventually separate from the bullet body (2). The end of the expansion is reached when the hydrodynamic forces become lower than the resistance of the bullet body.

The Figure 3 shows the shape of the impression obtained by firing a 30-caliber ammunition according to the invention in a block of Plastiline®.

The ball used conforms to that of the Figure 1 . The boom has a length of 16 mm for a diameter of 2.5 mm, is inserted in an axial hole of 17 mm, and protrudes 3 mm on the front. The mass of the ball in flight order is 9 g and its impact velocity on the target, perpendicular to it, is about 770 m / s.

The bullet has formed a cavity in the target block, and an impression has been cast in this volume, which makes it possible to visualize the effects of the internal arrow (3) on the one hand, and the bullet body (2) on the other hand.

The Figure 3 shows that a channel (17) of about 3.5 cm in diameter (a) and 3.5 cm in length (b) was formed in the target (16). The channel (17) is extended by the main cavity (18) formed by hydrodynamic cavitation phenomenon resulting from the progressive expansion of the ogival head (4) and the central portion (5) of the bullet body (2), while that the channel (17) corresponds to the first phase following the impact on the target, where the front face (10) of the ogival head (4) is not yet in contact with the target due to the hydrodynamic effect . The cavity (18) has a maximum diameter (c) of 10.5 cm, and its height (d) is 18.5 cm. Its diameter (e) in its extreme part is 2.1 cm, that is to say substantially equal to that of the ball body (2) expanded. The total depth of penetration of the bullet is 24.5 cm and the total volume of the cavity is 1.15 1. The helical cracks (19) on the entire wall of the cavity (18) reflect the work developed by the expansion of the ball.

For comparison, the Figure 4 illustrates the result of a shot obtained with a bimetallic bullet of the same mass, same impact velocity, at the same angle, in the same reference target, but provided with a fixed arrow whose point is set back by 3 mm from the front of the ogival head.

The Figure 4 shows that the impression obtained under the same conditions is "bottle" shape, that is to say without input channel. The cavity (20) formed in the target has a volume of 1.20 l, its maximum diameter (g) is 11.5 cm and this value is observed as soon as it enters the target, and its depth (h) is 19.5 cm.

This comparison of Figures 3 and 4 shows the difference in results obtained with a ball according to the invention, on the one hand, and a ball according to a known technique, on the other hand. It is also noted that the volume of the cavity formed by hydrodynamic cavitation is substantially identical in both cases, but that the total penetration of the ball is 25% greater in the case of the invention.

As shown in Fig. 5 , a sub-calibrated bullet (21) is equipped with a stabilizer (22) at its rear portion, and comprises a lead-free metal bullet body (23) carrying an inner arrow (24) projecting from the front portion. This bullet is housed in a throwing shoe (25), the assembly being placed in a usual way in a primed and loaded sleeve.

The bullet body (23) is monobloc, and has a nose (26) in its front part. The outer surface of the central portion has adents (27) cooperating with grooves (28) formed in the inner face of the throwing shoe (25). Longitudinal ribs (29) are formed on the surface of the inner shaft (24) which is partially inserted into a hole (30) drilled in the axis of the bale and opening on the end face (31) of the bale through the ogive (26).

An open conical cavity (32) is provided in the front face of the nose (26), forming with it an expansion lip (33).

The under-calibrated bullet represented on the Figure 5 can be advantageously used in a shotgun with a smooth or weakly scratched gun, for firing distances not exceeding 100 m.

Because of the relatively low initial velocity, of the order of 400 to 600 m / s, for this type of hunting weapon, the dimensioning of the nose (26), the conical cavity (32), the expansion lip (33), and the boom (24) is adapted according to the usual aerodynamic and ballistic techniques, as well as the mechanical characteristics of the metal alloy used for the bullet body and the internal arrow.

The Figure 6 represents an alternative embodiment of the hunting ball of the Figure 1 . The axial hole drilled in the ogival head (34) and partly in the central portion (35) of the bullet body has a narrowing. The front portion (36) of the hole has a diameter equal to that of the internal boom (37) to allow the sliding of the latter to the impact on the target. The rear portion of the hole (38) has a smaller diameter, thus forming a shoulder (39) at the junction of the two parts of the hole, which serves as a stop limiting the recoil of the inner boom (37).

The respective lengths of the two front (36) and rear (38) portions of the axial hole may be chosen according to the conditions provided for firing, in particular as a function of the hardness of the target to be treated. Thus, an advanced locking of the recoil of the internal boom (37) can be obtained by a shorter front portion (36) and a longer rear portion (38), and the hydrodynamic channel produced by the internal boom (37) will then be longer, for example for very hard and very resistant targets. Conversely, a delayed blocking of the deflection (37) will produce a shorter hydrodynamic channel, for the treatment of less hard and less resistant targets.

The Figure 7 represents another variant of the invention comprising two internal arrows (40) and (41) mounted one behind the other in the axial hole and separated by a distance (1).

The locking of the front internal arrow (40) is obtained when it slides until it comes into contact with the rear internal arrow (41). As in the previous example, the setting of the distance (1) separating the two arrows can be adjusted for very hard targets, if this distance (1) is reduced, or less hard targets, if this distance (1) is longer, thus contributing to a modulated expansion effect depending on the target.

Until the total expansion of the bullet body (42), the hard parts that may be encountered in the target are taken into account firstly by the front internal deflection (40) and then by the rear internal deflection ( 41) after ejection of the front internal deflection (40).

In the variant shown on the Figure 8 the internal arrow (43) has frustoconical ends (44) and (45). The frustoconical shape of the front end (44) facilitates the beginning of the expansion movement of the ogival head (46), especially for firing at targets of average or low resistance.

This frustoconical shape (44) cooperates with the open frustoconical cavity (47) surrounding the internal deflection (43) and makes it possible to reduce the length of the hydrodynamic channel produced by the penetration of the arrow into the target by reducing the hydrodynamic pressure.

Tests carried out using ammunition according to the present invention, drawn on blocks of inert material (Plastiline®), have demonstrated an excellent efficiency, and in particular a deformation by controlled and delayed expansion of the bullet on impact. on the target, as shown by Figures 3 and 4 . The invention is applicable to arrow ammunition for all weapons, especially hunting weapons of all calibers, smooth or striped barrel.

Claims (15)

1. A round for small, medium and large caliber guns, consisting of a full-caliber or subcaliber bullet, of the type comprising a bullet body (2) comprising an ogival head (4) and able to carry fins, and a supported internal dart (3) inserted into an axial hole (8), the internal dart (3) being disposed such that it protrudes with respect to the front face (10) of the bullet body, and characterized in that the internal dart can slide on impact with the target, and penetrates an open conical cavity (11) formed in the front face (10) of the ogival head (4).
2. The round as claimed in claim 1, characterized in that the cross section of the internal dart is, over the whole of its length, less than or equal to the diameter of the axial hole (8).
3. The round as claimed in claim 2, characterized in that the conical cavity (11) is combined with an expansion lip (12) formed at the junction between the conical cavity and the transverse face (10) of the ogival head.
4. The round as claimed in any one of claims 1 to 3, characterized in that the open conical cavity (11) has a shape such that the angle between its generatrix and the axis of the dart (3) is between 10 and 50°.
5. The round as claimed in any one of claims 1 and 2, characterized in that the internal dart (3) is constituted by a single homogeneous element.
6. The round as claimed in any one of claims 1 and 2, characterized in that the internal dart (3) is constituted by at least two consecutive elements disposed in an adjoining manner on the same axis.
7. The round as claimed in any one of claims 1 and 2, characterized in that the internal dart is constituted by at least two consecutive elements (40, 41) disposed on the same axis and separated by a gap.
8. The round as claimed in any one of the preceding claims, characterized in that the internal dart comprises frustoconical ends (44, 45).
9. The round as claimed in any one of the preceding claims, characterized in that it comprises a limiter of the backward movement of the internal dart.
10. The round as claimed in claim 9, characterized in that the backward movement limiter is constituted by a reduction in the diameter of the rear part (38) of the hole (8) receiving the dart.
11. The round as claimed in claim 9, characterized in that the backward movement limiter is constituted by a second dart (41) placed at the bottom of the hole receiving the darts.
12. The round as claimed in any one of the preceding claims, characterized in that the internal dart (3) is constituted by rod which is a solid of revolution comprising longitudinal ribs (7) on part of its surface.
13. The round as claimed in claim 12, characterized in that the front part of the body of the bullet comprises fracture initiators.
14. The round as claimed in any one of the preceding claims, characterized in that the internal dart (3) is made of steel, titanium, brass, copper, aluminum alloy or an engineering plastic of very high rigidity.
15. The round as claimed in any one of the preceding claims, characterized in that the body of the bullet (2) is made of copper or of brass containing 5 to 40% zinc, or of a composite based on tungsten or bismuth.

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