Neckless cartridge

Abstract

A cartridge with a composite cartridge case includes a projectile with an ogee-shaped tip and a bottom end ending in a base, a flangeless tubular case delimiting a chamber accommodating a propulsive powder, closed at a first longitudinal end by a base with a primer and at the second end opposite to the first, by the base of the projectile, a part of the flangeless tubular case fitting snugly around part of the projectile and having itself, at least in part, a frustoconical external shape, the cartridge being characterized in that: the chamber accommodating the propulsive powder includes, at the projectile end, a reduction in its diameter over all or part of the periphery thereof down to the diameter of the base of the projectile, the ratio between the length of the tip of the projectile and the maximum diameter thereof is greater than or equal to 2.9.

Claims

1. A cartridge comprising: a projectile with an ogival-shaped nose and a base ending with a head; and a polymer neckless tubular case defining a propellant powder receiving chamber closed at a first longitudinal end by a head with a primer and at a second longitudinal end that is opposite to the first longitudinal end by the head of the projectile, with a portion of the neckless tubular case enclosing a portion of the projectile and the portion of the neckless tubular case enclosing a portion of the projectile having, at least in part, a frustoconical external shape, wherein the propellant powder receiving chamber has, on the projectile side, a reduction of the diameter of the propellant powder receiving chamber over at least part of the periphery of the propellant powder receiving chamber up to the diameter of the head of the projectile, the ratio between the length of the nose of the projectile and the maximum diameter of the projectile is greater than or equal to 2.9, the projectile has a base having, at least in part, a gradual reduction of the diameter of the base up to the head of the base, and the case has, at the second longitudinal end of the case and in the head-projectile direction, a first portion having, over at least part of the perimeter of the first portion, a gradual reduction of the internal diameter of the first portion up to the head of the projectile, a second portion of an external diameter equal to the diameter of the first portion and of an increasing internal diameter conforming to a portion of the base of the projectile and then a terminal portion constituted by a shoulder, an inner face of the shoulder being in contact with the projectile.

2. The cartridge according to claim 1, wherein the ratio between the length of the nose of the projectile and the diameter of the projectile is between 2.9 and 4.1.

3. The cartridge according to claim 1, wherein the reduction of the diameter of the combustion chamber up to the diameter of the head of the projectile corresponds to a gradual reduction of the internal diameter of the case, the case having, at this level, a frustoconical shape with a half-angle between 20 and 40 degrees.

4. The cartridge according to claim 1, wherein the length of the second portion is at least equal to a third of the length of the terminal portion.

5. The cartridge according to claim 1, wherein the caliber of the cartridge is 5.56 mm.

6. The cartridge according to claim 5, wherein the caliber of the cartridge is 5.56 mm and the maximum length of the cartridge is 57.4 mm (2.26 in).

7. The cartridge according to claim 1, wherein the ratio between the length of the nose of the projectile and the diameter of the projectile is about 3.5.

8. The cartridge according to claim 1, wherein the caliber of the cartridge is 7.62 mm.

9. The cartridge according to claim 1, wherein the caliber of the cartridge is 12.7 mm.

10. The cartridge according to claim 8, wherein the caliber of the cartridge is 7.62 mm and the maximum length of the cartridge is 71.9 mm (2.83 in).

11. The cartridge according to claim 9, wherein the caliber of the cartridge is 12.7 mm and the maximum length of the cartridge is 140.8 mm (5.545 in).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and features will become apparent from the description of several embodiments of the invention, with reference to the appended figures in which:

(2) FIG. 1 shows a metal case cartridge with a bottle shape and a center fire,

(3) FIG. 2 shows a cartridge comprising a polymer tubular case,

(4) FIG. 3a shows a diagram of a longitudinal section of a cartridge according to a first embodiment of the invention with respect to a cartridge according to FIG. 1,

(5) FIG. 3b shows an enlarged portion of FIG. 3a, in this case of the portion of the end of the case located on the projectile side,

(6) FIG. 4a shows a diagram of a longitudinal section of a cartridge according to a second embodiment of the invention,

(7) FIG. 4b shows an enlarged portion of FIG. 4a, in this case of the portion of the end of the case located on the projectile side.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) FIG. 3a shows a diagram of a longitudinal section of a cartridge according to a first embodiment of the invention with respect to a cartridge according to FIG. 1.

(9) This cartridge 20, of a 7.62 mm caliber, comprises, on the one hand, a projectile 29 with an ogival-shaped nose 30, and a cylindrical base 31 ending with a head 32 and, on the other hand, a bottle-shaped tubular case 21 made of polymer and containing a propellant powder charge 22 and receiving, at a first longitudinal end 23, a head 24 with a primer 25, and comprising, at its second longitudinal end 26, and in the head 24-projectile 29 direction: a first portion 33 with a constant external diameter D1 and a gradual reduction of its internal diameter and then a second portion 34, with an external diameter D1 and a constant thickness, the inner face of which is completely in contact with the projectile and then a terminal portion constituted by a gradual reduction of its external diameter forming an external shoulder 27, the inner face of which is in contact with the projectile 29. The shoulder 27 is intended to cooperate with a part of a weapon adapted to fire this type of cartridge, with this part of the weapon being of a complementary shape and allowing to reproducibly position the cartridge longitudinally.

(10) Thus, the inner face 35 of the shoulder 27 is in contact with the projectile 29 and constitutes the terminal portion of the case 21 on the side of the projectile 29.

(11) The case is made of polymer and fixing the projectile to the case is obtained by overmolding. The head 24 is made of a light metal material, in this case aluminum. It is attached to the rear of the case by bonding or by threading/tapping.

(12) In this embodiment, the ratio between the length of the nose of the projectile and its maximum diameter is equal to 3.5. In addition, the ratio of the length of the second portion to the length of the third portion is about 0.6.

(13) The case body is characterized by an absence of a neck, rendered useless by the overmolding process. The connection between the case and the projectile is now at said second and third portions 31 and 27, thereby ensuring an excellent mechanical strength of the assembly, ensuring the concentricity thereof and using the space freed by removal of the neck to lengthen the nose of the projectile and thus reduce its drag.

(14) Said drag reduction is essential since it allows, while ensuring the required trajectory concordance with existing loads, either to use a lighter projectile fired at the same initial speed, or a projectile with the same mass fired with a reduced initial speed.

(15) In both cases, this allows to reduce the initial kinetic energy which concurs with the required reduction of the propellant charge caused by the use of composite cases and this without reducing the final performance at medium or long distance.

(16) Such a composite ammunition with an added-on light alloy head, assuming the external profile of the 7.6251 mm ammunition, having a case with a capacity of 2.85 cm.sup.3, against 3.5 cm.sup.3 for the brass-cased 7.6251 mm ammunition, and equipped with a lead-free projectile with a mass of 8.4 grams with a reduced drag, propelled at an initial speed of 830 m/s in a 61 cm long tube, essentially provides the same performance at 600 m as the M80-type loading with an ordinary bullet, but with a recoil reduced by an order of about 20%, related to the reduction of the propellant charge and of the projectile mass, and a shot mass reduced by almost 40% thanks to the gains on the case, on the projectile and on the powder mass.

(17) For a machine-gunner using a weapon in that caliber, and having an allocation of 800 cartridges, this represents a gain of almost 8 kg, with the reduction of the recoil of the weapon allowing a significant gain in accuracy, and the reduction of the powder mass allows to limit the warm-up of the weapon at the same practical rate of fire.

(18) Removing the neck releases a side vent of 0.45 mm on either side of the projectile, which must pass an additional leap of 8.16 mm before coming into contact with the forcing cone and taking up the rifling. In order to prevent this leap from causing a loss of accuracy, the foot of the ogive has a tangential profile which allows it to self-center upon arrival on the forcing cone.

(19) The use of a projectile both longer than the original one and made of a material less dense than lead implies an important stress on its gyroscopic stability. In order to maintain a value consistent with military use, the projectile has a recessed base, such as encountered on the so-called Mini bullets or on the Very High Speed-type projectiles marketed by the company SFM in the early 80s.

(20) This recess remains of a small diameter to prevent any expansion or fragmentation risk of this hollow base, even after a 180 tilt on its axis, which may occur in the event of an impact in a semi-liquid medium.

(21) If the given example focuses on the comparison with the 7.6251 mm cartridge, it is of course applicable to any conventional bottle-type ammunition for a long weapon, with equivalent gains such as, for example, a reduction of the mass of the shot and a reduction of the recoil at iso-performance.

(22) FIG. 4 shows a cartridge 40 according to a first embodiment of the invention.

(23) This cartridge 50 comprises, on the one hand, a projectile 49 with an ogival-shaped nose 40 and a base 51 having a gradual reduction of its diameter up to its head 52 and, on the other hand, a bottle-shaped tubular case 41 made of polymer, containing a propellant powder charge 42, and receiving at a first longitudinal end 43 a head 44 with a primer 45, and comprising, at its second longitudinal end 46, and in the head 44-projectile 49 direction, a first portion with a constant external diameter D1 and a gradual reduction of its internal diameter, a second portion 54 of an external diameter D1 and an increasing internal diameter conforming to a corresponding portion of the projectile base and then a terminal portion constituted by a gradual reduction of its external diameter forming an external shoulder 47, the inner face of which is in contact with the projectile.

(24) The gradual reduction of the internal diameter of the case is such that it has, at this level, a frustoconical internal shape, and preferably I.

(25) Thus, the inner face 55 of the shoulder 47 is in contact with the projectile 49 and constitutes the terminal portion of the case 41 on the side of the projectile 49.

(26) The case is made of polymer and fixing the projectile to the case is obtained by overmolding. The head is made of a light metal material, in this case aluminum. It is attached to the rear of the case according to the embodiment shown in U.S. Pat. No. 2,862,446.

(27) In this embodiment, the ratio between the length of the nose of the projectile and its maximum diameter is equal to 3. This curtailed head projectile profile type allows a significant drag reduction, mainly in the subsonic range, and therefore at long distances, with a slight decrease in performance at short and medium distance, due to the instabilities at the exit of the mouth.

(28) Of course, without departing from the scope of the invention, a nozzle could be made even with a projectile according to FIG. 3a by making a tubular case comprising, on the projectile side, a gradual reduction of its internal diameter up to a diameter smaller than that of the head of the projectile and then an increase of this internal diameter up to that of the head of the projectile.