AMMUNITION

Abstract: Ammunition for firing from the barrel of a gun, for example a tank gun, comprises a canister (2) containing layers of pellets (13). The body (8) of the canister (2) remains intact while passing through the barrel and breaks up shortly after leaving the barrel such that the pellets are discharged over a conical zone. Break up of the body (8) is achieved by buildup of internal gas pressure during firing, the body (8) having predetermined zones of weakness to ensure a predetermined pattern of breakup.

Description: AMMUNITION The present invention relates to ammunition and more particularly, but not exclusively, to ammunition for tanks. There has been proposed ammunition for tank guns or other large calibre ordnance comprising a canister filled with pellets or other fragmentary matter -which is dispersed over a wide area when the ε-mmunition is fired. The primary purpose of this ammunition is as anti-personnel ammunition, but it also has effectiveness in clearing barbed wire or foliage, or against light skinned vehicles. With the previously proposed ammunition, the canister tends to break up whilst it is moving through the barrel during discharge thereby releasing the pellets or other fragmentary matter within the barrel, ■ which results in significant wear and damage to the inner surface of the barrel. According to the present invention there is provided ammunition for firing from the barrel of a gun, comprising a canister containing pellets or other fragmentary material, and means for admitting propellant gas into the casing during firing whereby to permit a build-up of internal pressure within the canister during passage along the barrel, said canister having predetermined zones of weakness, the configuration being such that the structural integrity of the canister is maintained whilst moving through the barrel and after leaving the barrel the canister starts to break up at the zones of weakness under the internal gas pressure whereby to effect dispersal of the fragmentary material. Advantageously the ammunition includes a sealing ring rotatably mounted on the canister in order to provide a gas seal with the surface of the barrel without inducing substantial spin to the canister. In a preferred embodiment the canister is formed by a tubular body closed at its forward end by a cap and at its rear end by a base, the base preferably including orifices to permit propellant gas to bleed into the interior of the body. The body is formed with zones of weakness which permit the body to separate into discrete longitudinal strips on breaking up. A connection between the cap and the body defines a zone of weakness which is designed to ensure that the cap breaks away from the body at the start of break-up of the canister, followed by breaking up of the body by separation and dispersal of the discrete longitudinal strips. This configuration provides dispersal of the fragmentary material in a concentrated cone starting at a position forwardly of the barrel. An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:- Figure 1 is a side elevation partially in section showing ammunition in accordance with the preferred embodiment and consisting of a canister attached to the forward end of a propellant case; Figure 2 is a side elevation partially in section of the canister; Figure 3 is a longitudinal section through the canister but showing the canister at a stage during manufacture -while it is open at its front end prior to loading with pellets; and Figure 4 is a transverse section through the body of the canister prior to loading with pellets. The ammunition in accordance with the preferred embodiment of the invention is designed for use in a tank gun or other large calibre ordnance and comprises a canister 2 packed with pellets such as cylindrical metal pellets. As will be explained in detail hereinafter, the canister 2 is designed to remain intact whilst moving through the barrel and does not start to break up until shortly after the canister 2 has left the barrel. The construction of the canister ensures that the pellets are dispersed in a concentrated conical formation starting from approximately 5 metres in front of the barrel. More particularly as shown in Figures 1 and 2 the ammunition comprises the canister 2 mounted at the forward end of a standard case or cartridge 4 containing a primer 6, and a propellant charge. The canister 2 comprises a tubular metal body 8 closed at its forward end by a cap 10 and at its rear end by a base 12. The body 8 is filled with cylindrical metal pellets 13 arranged in layers. The manner in which the body 8 cooperates with the base 12 is shown in detail in Figure 2. The base 12, which is preferably of steel, has at its forward end an annular rebate -which receives the rear end of the tubular body 8 so that the external surface of the tubular body 8 is flush with the external surface of the base 12. The rear end of the tubular body 8 is secured within the annular rebate by welding, preferably by electron beam welding for reasons which will be discussed hereinafter. A shallow annular groove 14 is provided towards the rear end of the base 12 to permit attachment of the canister 2 to the case 4 by swaging of the forward end of the case 4 into the annular groove 14. A larger annular groove 16 of rectangular section forwardly of the swaging groove 14 serves to receive an obturator ring 18 ■ which provides a gas seal against the interior surface of the barrel. The base 12 is of cup-like configuration open towards the rear. The forward wall of the cup-shaped base 12 is pierced by a series of orifices 20 (three orifices in the example shown) in order to permit bleeding of propellant gas through the base 12 into the interior of the canister on firing in order to permit a build-up of internal pressure within the canister which facilitates breaking up of the canister after it has left the barrel. The obturator ring 18 which fits within the rectangular section groove 16 is, as explained above, provided in order to form a gas seal with the interior surface of the barrel in order to prevent propellant gas from escaping around the exterior of the canister on firing. In a conventional shell, a similar sealing function is provided by a band of soft metal which, on firing, deforms into the rifling on the interior of the barrel to form a driving connection between the rifling and the shell whereby to cause the shell to spin at high velocity. This of course requires there to be a firm connection between the band and the shell. In the present embodiment, the obturator ring 18 is able to spin within the groove 16. The ring 18 is formed of a material which is capable of providing a gas seal but is such that it does not bind within the annular groove 16. On firing, the ring 18 will engage within the rifling but will spin within the groove. Although friction between the ring 18 and the groove 16 will cause some spinning of the canister, the spin rate will be comparatively low, typically around 2,500 r.p.m. The ring 18 is applied to the base 12 after assembly of the canister and is formed as a split ring with an oblique split in order to ensure that a gas seal is established even in the zone of the split. The avoidance of a high spin rate by use of the ring -which spins within the groove 16 contributes to the maintenance of the structural integrity of the canister during its passage through the barrel, by avoiding the consequent generation of high centrifugal forces which could cause breakage of the canister within the barrel. Typically the spin rate of the canister would be of the order of 2,500 r.p.m. in contrast to a spin rate of around 25,000 r.p.m. or more for a conventional shell fired from a tank gun. In this respect, the canister of the preferred embodiment of the invention is intended for short range use with dispersion over a relatively wide area and hence does not require a high spin rate which would be necessary for long range accuracy for a conventional shell. Although no spinning of the canister is actually required, nevertheless some spinning does occur due to frictional forces between the rapidly spinning obturator ring 18 and the wall of the groove 16 in which it is mounted. In order to minimise the spin rate of the canister, the material from which the ring 18 is made should be a low friction material. The ring must also have stability in size over a long period of time and over a wide temperature and humidity range. The specific material must also not become brittle with age. The material must also be such that it does not extrude onto the surface of the barrel under the heat and pressures generated on firing of the propellant charge. Ammunition of this type may be kept in storage over a period of years and it is essential that the characteristics of the ring are maintained throughout the specified storage life of the amm * unitiόn. Grades of nylon have been found suitable for the ring. Nylon 11 produced by Aquitaine Total Organo under the trade mark "RILSAN BMN P20" has been found to be particularly satisfactory. It is envisaged, however, that there may also be other plastics materials which will possess the required characteristics. The forward end of the body 8 is closed by the cap 10 which may be fabricated from a suitable plastics material such as nylon, the forward end of the body 8 being received within an annular rebate at the rear end of the cap 10 so that the body 8 is flush with the circumferential surface of the cap 10. The construction of the canister is such that its structural integrity is maintained whilst within the barrel, but shortly after leaving the barrel the canister starts to break up under the internal gas pressure to effect dispersion of the pellets. The breaking up of the canister occurs in a relatively controlled manner and is achieved by incorporating zones of weakness within the tubular body 8 itself and also at the areas of connection of the body 8 to the cap 10 and the base 12. A welded connection of the body 8 to the base 12 by electron beam welding as described previously provides a welded connection of a determined and repeatable strength and -which can therefore be set to provide a strength of connection -which can be controlled in order to form a zone of weakness at the rear end of the body 8. The connection between the body 8 and the cap 10 is provided by mechanical fasteners in the form of blind rivets 24 circumferentially arranged around the forward end of the body 8. This form of riveted connection also provides a zone of relative weakness at the forward end of the body 8. The strength of the connection at the forward end of the body 8 is such as to withstand the build-up of internal gas pressure while the canister is within the barrel, but it starts to break shortly after the canister leaves the barrel to permit removal of the cap 10 and hence dispersal of the pellets. The construction of the cap 10 and its method of attachment to the body 8 is capable of variation ■ within the scope of the invention. In order to permit the build-up of internal gas pressure, a seal is provided between the cap 10 and the body 8. As shown in Figure 2, the seal is in the form of a sealing disk assembly 26 having a forward end face abutting against the base wall of the cap 10 and a peripheral edge in contact -with the internal surface of the body 8. The sealing disk assembly 26 is of sandwich construction comprising two outer disks 26a of metal and an inner disk 26b of a suitable synthetic rubber or plastics sealing material such as neoprene. The sealing disk assembly 26 is interposed between the base wall of the cap 10 and the packing of pellets 13 within the body 8. The pellets 13 are packed within the body in layers and the construction of the sealing disk assembly 26 provides a degree of compressibility axially of the body 8. This compressibility can be used to compensate for slight variations in pellet length when loading in order to ensure that the pellets are tightly held within the body 8 and also that a substantial gas seal is provided at the forward end of the body 8 between the body 8 and the cap 10. Apart from the zones of weakness in the connections of the body 8 to the cap 10 and base 12, the body 8 itself is also constructed with specific zones of weakness in order to achieve breaking up of the body in a relatively controlled manner shortly after discharge from the barrel. In the embodiment shown, the zones of weakness in the body are provided by constructing the body from a number of part-cylindrical abutting segments 8a (Figures 3 and 4) ■ which are connected by internal metal strips 8b which overlap the zone of each abutting joint and which are spot welded to the segments 8a at each side of the abutting joint. In the particular form shown, the body 8 is composed of three part-cylindrical segments 8a but this is not critical and the body could be composed of four or more such segments in order to vary the manner in -which the body breaks up after discharge from the barrel. The strength of the spot welded connection between each connecting strip 8b and the part cylindrical segments is an important factor in determining the overall strength of the body. The strength of the connection is a factor of the number of spot welds and also the spacing between spot welds and the strength of the body can be relatively easily controlled and, if necessary varied, simply by altering these factors and this does permit relatively straightforward "fine tuning" in design in order to provide the required dispersal characteristics of the pellets. This form of construction is able to provide consistency in the predictability of the break¬ up characteristics of the body so that consistent pellet dispersal characteristics can be obtained for the ammunition. The necessary strength can be obtained by fabricating the part-cylindrical segments 8a and also the connecting strips 8b from mild steel. Although other means of construction could be used for the body, the above means is of advantage as it provides a relatively inexpensive means of construction with zones of weakness which will permit break-up in a predictable way and with the facility for relatively easy variation of the strength of the zones of weakness. As previously explained, the structural integrity of the canister is maintained while the canister is moving through the barrel after firing. During this phase, internal gas pressure builds up within the canister by bleeding of the propellant gas through the orifices 20 in the base 12. After discharge from the barrel, the canister starts to break up under the effects of the gas pressure. In order to obtain the required dispersal characteristics of the pellets in the form of a relatively dense cone it is desirable that breaking up of the canister commences at the front end of the canister by separation of the cap 10 from the body 8. The circumferential zone of weakness created at the front end of the canister by means of the riveted connection between the cap 10 and the body 8 and which is significantly weaker than the connection between the body 8 and the base 12 ensures that this occurs. The individual part-cylindrical segments 8a forming the body 8 then start to fold or peel in an outwards direction and then separate at their rear ends from the base 12. The separation of the segments 8a from the base 12 is of importance because the maintenance of a connection between the segments 8a and the base 12 would result in the segments 8a confining the pellets 13 and hence impeding the dispersion of the pellets 13 over a sufficient cone angle. The connection of the segments 8a to the base 12 by electron beam welding provides a dete-rminable strength of the connection between the segments 8a and the base 12 and which is repeatable from canister to canister. This welding technique also avoids distortion of the components during welding and hence avoids the necessity of any subsequent machining. In practice, an effective anti-personnel ammunition can be obtained by designing the strength characteristics of the canister to effect dispersion of the pellets in a cone ∞mmencing about five metres beyond the barrel and over a cone angle of around 10 °. Ammunition in accordance with the invention designed for use with a 105mm tank gun has been found to be effective at up to 300 metres. The ammunition provides a very effective anti-personnel function and can be used to protect tanks against massed infantry attack as discharge of the ammunition towards a friendly tank will not penetrate the armour of the tank itself. The ammunition would however be effective against soft skinned vehicles such as trucks. The ammunition is also effective in clearing barbed wire to provide a path through the wire- for tanks or infantry and is effective against foliage in order to defoliate an area of dense foliage. The retention of canister integrity within the barrel and also the relatively low spin rate of the canister within the barrel results in relatively low barrel wear. The embodiment has been described by way of example only and modifications are possible within the scope of the invention.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. Ammunition for firing from the barrel of a gun, comprising a canister containing pellets or other fragmentary material, and means for admitting propellant gas into the casing during firing -whereby to permit a build-up of internal pressure within the canister during passage along the barrel, said canister having predetermined zones of weakness, the configuration being such that the structural integrity of the canister is maintained whilst moving through the barrel and after leaving the barrel the canister starts to break up at the zones of weakness under the internal gas pressure ■ whereby to effect dispersal of the fragmentary material. 2. Ammunition according to claim 1, further comprising a sealing ring rotatably mounted on the canister to provide a gas seal with the barrel without inducing substantial spin to the canister. 3. Ammunition according to claim 2, wherein the sealing ring is composed of a low friction plastics material which retains its integrity upon firing of the ammunition. 4. Ammunition according to any one of claims 1 to 3, -wherein the canister comprises a tubular body closed at its forward end by a cap and closed at its rear end by a base. 5. Ammunition according to claim 4, -wherein the body includes zones of weakness which permit the body break up by separation into discrete longitudinal strips, and the cap is connected to the body by a connection which enables separation of the cap prior to breaking up of the body. 6. Ammunition according to claim 5, -wherein the strength of the connection between the cap and the body is substantially less than that between the base and the body whereby during break-up of the body the longitudin- strips fold in an outwards direction and then separate at their rear ends from the base. 7. Ammunition according to claim 6, -wherein the connection between the body and base is formed by electron beam welding. 8. Ammunition according to any one of claims 5 to 7, wherein the connection between the cap and body is formed by a series of mechanical fastening means. 9. Ammunition according to any one of claims 4 to 8, -wherein the body is defined by an array of part-cylindrical strips with adjacent edges of adjacent strips being in abutting relation, and adjacent strips are connected by a connecting strip internally of the body and overlapping the adjacent edges of the part-cylindrical strips. 10. Ammunition according to claim 9, wherein the connecting strips are spot welded to the part-cylindrical strips. 11. Ammunition according to any one of claims 4 to 10, wherein the means for admitting propellant gas into the casing during firing comprises at least one orifice in the base to permit propellant gas to bleed into the interior of the body. 12. Ammunition according to any one of claims 4 to 11, wherein the pellets are packed in layers within the body between the cap and base. 13. Ammunition according to claim 12, further comprising a sealing disk interposed between the cap and the adjacent layer of pellets, said disk providing a gas seal between the cap and body and said disk being compressible axially of the body by the layers of pellets whereby the pellets are held tightly within the body.

Inventors: SCOLARO ANTHONY JOHN, THOMSON CAMERON, SCOLARO, ANTHONY, JOHN, THOMSON, CAMERON
Applicants: AUSTRALIAN DEFENCE IND LTD, AUSTRALIAN DEFENCE INDUSTRIES LTD.
Application year: 1992
Main classification: F41H11
IPC codes: F42B12