GB1605360A - Propellent charge body for caseless ammunition - Google Patents

Description

(54) PROPELLENT CHARGE BODY FOR CASELESS AMMUNlON VWe DAMrr NOBEL AxiTENGEsELLsasAFr, a German Company, of 521 Troisdorf, Near Cologne, Germany, do hereby declare the invention, for which Vwe pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a propellent charge body for use in caseless ammunition.

Propellent charges for caseless ammunition are usually formed from such secondary explosives as nitrocellulose. Unfortunately, these propellent charges possess the following disadvantages: their self-ignition temperature at approximately 1 750C is so low that the propellent powder of a cartridge newly introduced into a cartridge chamber may undergo spontaneous ignition as a result of the heat present in the chamber from previous firings. This applies in particular to machine guns operated with a high firing rale. With machine guns, the cartridge chamber becomes very hot after only a shon time on account of the high firing rate.This results in irregularities or increases in the gas pressure and hence in an unacceptable, incontrollable effecl upon the internal ballistics of the powder and affects the automatic functioning of the weapon. Hence, there is an increased risk of accidents.

In order to overcome these problems, attempts have hitherto been made to use secondary explosive substances having a higher self-ignition temperature than nitrocellulose together with desensitising binders as propellent powders.Examples of explosives of this type are for example, hexogen, guanidine nitrate, hexanitrodiphenylamine, dipicryl sulphone, hexanitrostilbene and tetranitrobenz 1 ,3a4 ,6a tetm-aia-pentalene. All of these explosives characleristically have self-ignition temperatures of at least 230"C. Unfortunately, mixlures of these explosives with binders possess the disadvantage that they only bum up completely in very high pressure ranges, generally at pressures exceeding 5000 bars. Bum-up is incomplete in lower pressure ranges, al which the cartridge chamber becomes soiled and the velocity of the bum-up reaction tends to vary over a fairly wide range.

The residues obtained in the lowcr pressure ranges consisl largely of sunburnt reaction products, because the calorific valuc and oxygcn value of the secondary explosive are reduced very considerably by the binder. However, the binder content cannot be reduced at will because, in the presence of very small quantities of binder, tlle combustion process leads to detonation-like reactions in crystalline subregions of the explosive substance.

According to the present invention, there is provided a propellent charge body for caseless ammunition, which body comprises an outer layer of a propellent charge composition comprising a secondary explosive having a selfignition point of at least 230"C and a binder present in an amount of from 2 to 40% by weight of the outer layer, the outer layer surrounding an inner propellent charge core which is formed of an explosive substance or composition having a self-ignition temperature lower than that of the outer layer, with the proviso that when a-octogen is the sole explosive component of said core, it is not a sole explosive component of the outer layer.

A propellent charge embodying this invention has the characteristic advantages of not igniting spontaneously at temperatures of up to around 200 C, and while containing hitherto described explosive substance binder mixtures whose explosive components self-ignite only above 230"C, i.e. at high temperature, does not leave any unburnt residues. In addition, the intemal ballistic of these propellent charges are at least equivalent to those of nitrocellulose powder.

In order to build up a propellent charge body having the desired ignition and combustion behaviour, it is possible to include one or more equidistant propellent charge inner layers disposed between the core and the outer layer, the or each inner layer being formed of an explosive substance or composition which has a self-igr.ition temperature lower than that of the outer layer and which is the same explosive substance or composition or a different explosive substance or composition to that of the core.

The propellent of which the propellent charge core is formed and of which the or each inner layer which may be present may be formed, is preferably a p.opellent charge based on nitrocwlluiose which can be used alone.

However, it is also possible to use powder-form a-oclogen suitably desensitised by means of a binder for this purpose.

By the expression "equidistant" as used herein is meant an arrangement of one or more inner layers of which all positions on the outer and inner surface of a particular layer are always respectively at the same shortest distance from the outer surface of the propellent body as a whole. Accordingly, the individual layers must have a uniform thickness. For example, the layers may be arranged concentrically around a projectile axis, or an imaginary extension thereof, or about the centre point of the propellent charge core.

When distinct inner charge layer(s) is/are present and it/they and the propellent charge core have the same composition, the equidistant layer(s) may be considered to be in an arrangement in which the outer layer of the propellent body comprising secondary explosive of high self-ignition temperature uniformly surrounds the entire inner charge i.e. the inner charge core and the inner layer(s) surrounding it and only burns up after the inner charge has bumt up. in this case, therefore, the entire outer layer is at a uniform distance from an igniting charge for the inner charge.

Even when several inner charges formed of different explosive substances/compositions are present between the outer layer and a propellent charge core, the outer layer uniformly surrounds the entire inner charge. Accordingly, only the outer layer comes into contact with the cartridge chamber.

The ratio by weight of the outer layer to the inner charge(s) therewithin, that is inner layer or layers, if present, the core preferably amounts to from 1.2:1 to 0.1:1. Accordingly, the outer layer may be heavier by at most about 20% than the inner charge(s). The minimum weight of the outer layer preferably amounts to 10% of the weight of the inner charge(s).

Propcllent charge bodies formed according to this invention do not possess the disadvantages of either pure nitrocellulose charges or the disadvantages of binders based on binder and secondary explosive. When a propellent charge body according to this invention is ignited by an igniting mixture, optionally followed by an ignition intensifying mixture, it is the inner charge(s) core formed prefcrably of nitrocellulose or of a-octogen desensitised by a binder which is the first to react. The entire energy of the inner charge(s) then activate(s) the inside of the surrounding propellant based on secondary explosive of high self-ignition temperature and binder.In this way, this propellant can undergo complete reaction in the cartridge chamber.

Propellent compositions which may be used for forming the outer layer are compositions of the type hitherto cmployed, inner alia, as propcllants for caseless ammunition for boltsetting apparatus. They contain crystalline secondary explosive substances having a sclfignition temperature of at least 230"C for example, the above-mentioned explosive substances hexogen, guanidine nitrate, hexanitrodiphenylamine, dipicryl sulphone, hexanitrostilbene and tetranitrobenzo-1,3aX,6a- tetra-aza-pentalene; other explosive substances which may be used are octogen, pentaerythritol tetranitrate, diarninonitrobenzene, triaminonitrobenzene and 2,4 ,6trinitrophenyl methyl nitramine (tetryl).These explosives are desensitised by binders; a large number of synthetic resins may be used as binders, including for example polyesters, polyamides, polyurethanes, polymethacrylates and polyvinyl butyral. The amount of binder in these outer propellent charges varies from 2 to 40% by weight, although it preferably amounts to from 14 to 22% by weight.

When formed of a conventional nitrocellulose propellant, the inner charge(s) is/ are formed either by pressing, by bonding or by extrusion. A shell of the propellant based on secondary explosive of high self-ignition temperature and a binder may then be bonded around this core of nitrocellulose propellant Another method of forming a propellent body according to this invention involves the simultaneous pressing of the explosive substance or composition of the inner charge(s) with the propellant charge composition of the outer layer. This method of production may be applied particularly well to two-piece ammunition which is subsequently bonded.

The following Examples illustrate this invention.

EXAMPLE 1 Ammunition was produced by a pressing technique. The ammunition consisted of two semi-cylindcrs which were bonded togethcr to form a cylinder after a projectile and a booster had been juxtaposed with respect thereto. Each semi-cylinder comprised an outer half shell and an inner cylindrical half shell placed therein.

Each half shell forming an outer layer consisted of 1.1 g of a mixture of octogen (87% by weight) and polyvinyl bulyral (13% by weight) which was initially introduced into a mould cavity. The inner semi-cylinder forming the inner layer of each of the semi-cylinders consisted of a more rcactive propellant of the following composition: 20% by weight of octogen, 60% by weight of triaminoguanidine nitrate (TAGN) and 20% by weight of polyvinyl butyral (PVB). These explosives were in finely divided form. The quantity of mixture forming the inner cylinder also amounted to 1.1 g.

The ignition temperature of the ammunition thus formed was above 215"C. The ignition temperature of ammunition produced for comparative purposes in the same way, but consisting cntircly of the above mentioned mixture of octogen, TAGN and PVB, was between 205 and 208do.

When the ammunition formed from the two compositions was fired in a weapon with an empty volume of 2600 mm3, the following intemal and extemal ballistic values were obtained: P,: 3522 + 175, -214 bar ED: 1.37 +0.15,-0.08ms V, : 1000 + 4, - 9 m/s.

EXAMPLE 2 Caseless ammunition was produced in the same way as in Example 1, its outer shell again consisting of 87% by weight octogen, 13% by weight polyvinyl butyral. The inner layer consisted of nitrocellulose. The ammunition was again produced by pressing. The outer shell contributed to 33% of the weight of the shell and the inner shell contributed 66% of the shell weight. The ballistic data obtained were the same as set out in Example 1.

The ignition temperature of this ammunition was 260"C, whereas the ignition temperature of comparison ammunition consisting solely of nitrocellulose was 1800C.

In both the foregoing Examples, the resinbonded propellent charges were produced by kneading the respective explosive substances in a kneader with the polyvinyl butyral dissolved in methyl acetate. The thoroughly kneaded mass was granulated, measured out and pressed.

For a better understanding of this invention and to show further how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, wherein: Figure 1 is a cross-section through a cylindrical propellent charge body of the type produced in Example 1; Figure 2 is a cross-section through a variant of the propellent charge body of Figure 1; and Figure 3 is a cross-section through a substantially rectangular propellent charge body.

The propellent charge body shown in Figure 1 comprises two halves which are bonded to one another in the region of a rectangular interface 3. Each half comprises an outer layer 1 of a charge of low temperature sensitivity and an inner layer 2, which in this case forms thc core of the propellent charge and which is more temperature-sensitive. The circular crosssectional form illustrated could of course be replaced by other cross-sectional forms. For example, the propellent charge body could even be formed with an elliplical or oval crosssection.

In the variant illustrated in Figure 2, additional inner layers 4, 5 and 6 consisting of charges of different composition are arranged between the outer layer 1 and the inner propellent charge core 2. Although the individual layers each have a uniform thickness, they may also differ from one another in thickness, as illustrated. In this casc, in addition, the propellent charge body is again made up to two halves produced by pressing which are bonded lo one another in the region of the interface 3.

Finally, Figure 3, in which like reference numerals represent like features in Figure 1, shows a propellent charge body having a substantially rectangular cross-section. Instead of this substantially rectangular cross-section, however, it would even be possible for example to select a square or other polygonal crosssection. The layer 1 shown in Figure 3 has substantially constant thickness throughout its cross-section.

WHAT WE CLAIM IS: 1. A propellent charge body for caseless ammunition, which body comprises an outer layer of a propellent charge composition comprising a secondary explosive having a selfignition point of at least 230"C and a binder present in an amount of from 2 to 40% by weight of the outer layer, the outer layer surrounding an inner propellent charge core which is formed of an explosive substance or composition having a self-ignition temperature lower than that of the outer layer, with the proviso that when a-octogen is the sole explosive component of said core, it is not a sole explosive component of the outer layer.

2. A propellent charge body as claimed in claim 1, which additionally comprises one or more equidistant, as hereinbefore defined, propellent charge inner layers disposed between the core and the outer layer, the or each inner layer being formed of an explosive substance or composition which has a self-ignition temperature lower than that of the outer layer and which is the same explosive substance or composition or a different explosive substance or composition to that of said core.

3. A propellent charge body as claimed in claim 1 or 2, wherein said core is formed of nitrocellulose.

4. A propellent charge body as claimed in claim 1, wherein said core is formed of an explosive composition comprising a -octogen desensitised by means of a binder.

5. A propellent charge body as claimed in any one of the preceding claims, wherein the outer layer is formed of hexogen, guanidine nitrate, hexanitrodiphenylamine, dipicryl sulphone, hexanitrostilbene or tetranitrobenz 1,3aX,6a-tctraza-pcntalene and a said binder.

6. A propellent charge body as claimed in any one of claims 1 to 4, wherein the outer layer is formed of octogen, pentacrytaritol tetranitrate, diaminonitrobenzene or tetryl and a said binder.

7. A propellent charge body as claimed in any one of the preceding claims, wherein the outer layer conlains from 14 lo 22% by weight of binder.

8. A propellent charge body, wherein the ratio by weight of the outer layer to the weight of said core or the total weight of said core and inner laycr(s) is from 1.2:1 to 0.1:1.

9. A propcllent charge body as claimed in claim 1, substantially as described in either of the foregoing Examples.

10. A propellent charge body, substantially

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. empty volume of 2600 mm3, the following intemal and extemal ballistic values were obtained: P,: 3522 + 175, -214 bar ED: 1.37 +0.15,-0.08ms V, : 1000 + 4, - 9 m/s. EXAMPLE 2 Caseless ammunition was produced in the same way as in Example 1, its outer shell again consisting of 87% by weight octogen, 13% by weight polyvinyl butyral. The inner layer consisted of nitrocellulose. The ammunition was again produced by pressing. The outer shell contributed to 33% of the weight of the shell and the inner shell contributed 66% of the shell weight. The ballistic data obtained were the same as set out in Example 1. The ignition temperature of this ammunition was 260"C, whereas the ignition temperature of comparison ammunition consisting solely of nitrocellulose was 1800C. In both the foregoing Examples, the resinbonded propellent charges were produced by kneading the respective explosive substances in a kneader with the polyvinyl butyral dissolved in methyl acetate. The thoroughly kneaded mass was granulated, measured out and pressed. For a better understanding of this invention and to show further how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, wherein: Figure 1 is a cross-section through a cylindrical propellent charge body of the type produced in Example 1; Figure 2 is a cross-section through a variant of the propellent charge body of Figure 1; and Figure 3 is a cross-section through a substantially rectangular propellent charge body. The propellent charge body shown in Figure 1 comprises two halves which are bonded to one another in the region of a rectangular interface 3. Each half comprises an outer layer 1 of a charge of low temperature sensitivity and an inner layer 2, which in this case forms thc core of the propellent charge and which is more temperature-sensitive. The circular crosssectional form illustrated could of course be replaced by other cross-sectional forms. For example, the propellent charge body could even be formed with an elliplical or oval crosssection. In the variant illustrated in Figure 2, additional inner layers 4, 5 and 6 consisting of charges of different composition are arranged between the outer layer 1 and the inner propellent charge core 2. Although the individual layers each have a uniform thickness, they may also differ from one another in thickness, as illustrated. In this casc, in addition, the propellent charge body is again made up to two halves produced by pressing which are bonded lo one another in the region of the interface 3. Finally, Figure 3, in which like reference numerals represent like features in Figure 1, shows a propellent charge body having a substantially rectangular cross-section. Instead of this substantially rectangular cross-section, however, it would even be possible for example to select a square or other polygonal crosssection. The layer 1 shown in Figure 3 has substantially constant thickness throughout its cross-section. WHAT WE CLAIM IS:

1. A propellent charge body for caseless ammunition, which body comprises an outer layer of a propellent charge composition comprising a secondary explosive having a selfignition point of at least 230"C and a binder present in an amount of from 2 to 40% by weight of the outer layer, the outer layer surrounding an inner propellent charge core which is formed of an explosive substance or composition having a self-ignition temperature lower than that of the outer layer, with the proviso that when a-octogen is the sole explosive component of said core, it is not a sole explosive component of the outer layer.

2. A propellent charge body as claimed in claim 1, which additionally comprises one or more equidistant, as hereinbefore defined, propellent charge inner layers disposed between the core and the outer layer, the or each inner layer being formed of an explosive substance or composition which has a self-ignition temperature lower than that of the outer layer and which is the same explosive substance or composition or a different explosive substance or composition to that of said core.

3. A propellent charge body as claimed in claim 1 or 2, wherein said core is formed of nitrocellulose.

4. A propellent charge body as claimed in claim 1, wherein said core is formed of an explosive composition comprising a -octogen desensitised by means of a binder.

5. A propellent charge body as claimed in any one of the preceding claims, wherein the outer layer is formed of hexogen, guanidine nitrate, hexanitrodiphenylamine, dipicryl sulphone, hexanitrostilbene or tetranitrobenz 1,3aX,6a-tctraza-pcntalene and a said binder.

6. A propellent charge body as claimed in any one of claims 1 to 4, wherein the outer layer is formed of octogen, pentacrytaritol tetranitrate, diaminonitrobenzene or tetryl and a said binder.

7. A propellent charge body as claimed in any one of the preceding claims, wherein the outer layer conlains from 14 lo 22% by weight of binder.

8. A propellent charge body, wherein the ratio by weight of the outer layer to the weight of said core or the total weight of said core and inner laycr(s) is from 1.2:1 to 0.1:1.

9. A propcllent charge body as claimed in claim 1, substantially as described in either of the foregoing Examples.

10. A propellent charge body, substantially

as hereinbefore described with reference to, and as shown in, any one of the Figures of the accompanying drawings.