WO2007119037A1

WO2007119037A1 - Primer compositions

Info

Publication number: WO2007119037A1
Application number: PCT/GB2007/000555
Authority: WO
Inventors: Michael Ernest Saxby
Original assignee: Utm Ip Limited
Priority date: 2006-04-13
Filing date: 2007-02-16
Publication date: 2007-10-25
Also published as: GB2437076A; GB0607472D0

Abstract

Primer compositions comprising phosphorus, an oxidising agent, an inert filler and a starch component are provided. The compositions are placed in percussion caps and are useful in training munitions.

Description

Primer Compositions

FIELD OF THE INVENTION

This invention relates to a novel primer composition, and particularly but not exclusively to a priming composition for percussion caps for small arms ammunition (SAA) capable of meeting military standards, its method of manufacture and to percussion caps and cartridges containing the composition. The primer composition of the present invention is particularly useful in the manufacture of training ammunition.

BACKGROUND ART

It is well known that the main propellant charge contained within the cartridge case of a round of ammunition is relatively insensitive and requires a significant amount of energy to ensure that rapid and complete ignition successfully occurs. This energy is conventionally provided by a primer composition located at the rear end of the cartridge case. Such primer compositions typically comprise an energetic material which is sensitive to the input of energy generated through heat, friction or percussion and provides in response thereto a flame and/or hot particulates for activating the propellant charge present in the cartridge.

A percussion primer typically comprises a cap formed of a cup having a priming composition therein. The cup is typically covered with waxed or varnished paper or the like to exclude moisture. The cap is then placed in a pocket in the cartridge case. In a Boxer primer, there is also an anvil pressed into the open end of the cup. For Berdan primers, the casing of the cartridge includes an anvil integrally formed therewith. In each case, ignition of the priming composition is initiated by the impact of the firing pin of a weapon against the central portion of the cup thereby compressing the priming composition between the anvil and the cup. The heat generated by the compressive and/or frictional forces generated within the cup causes the composition to ignite almost instantaneously,

CαNHRMAHOtf COPY and to burn very rapidly. The hot gases and/or particulates generated are forced into contact with the propellant through flash holes in the casing pocket. The energy generated by the burning of the primer/propellant combination typically causes the projectile to be expelled from the barrel of the gun at velocities in excess of 700ft/sec [ 213mtr/sec].

Common priming compositions typically comprise a main energetic ingredient, an oxidant and a sensitiser which increases the susceptibility of the main ingredient to the effect of the impact from the firing pin of the weapon. One or more secondary energetic ingredients and fuels, which modify the output of the primer, by for example providing more heat or producing more gas, hot particles may also be present.

With certain ammunition rounds, depending upon the design of the propellant, the production of a flame or hot gas only can be insufficient to promote efficient ignition of the propellant because the gas only tends to impact and activate the surface region of thereof. Activation of the remaining propellant therefore depends upon the propagation of the primer initiated reaction from the surface region of the propellant throughout the remaining volume. Efficient propagation of the primer initiated reaction can be achieved through the incorporation into the primer of particulate matter, which generates hot particles upon ignition of the primer. The production of hot particles can be beneficial to the subsequent ignition of the propellant, because they can be directed in such a way that they are able to efficiently penetrate the propellant and simultaneously cause activation thereof over a larger volume than would otherwise be the case.

Many priming compositions contain heavy metal elements as their principle components. For example, lead styphnate is typically used as a main energetic component; barium nitrate is a common oxidant and antimony sulphide is a common fuel. The presence of heavy metal elements in priming compositions is undesirable due to environmental concerns and priming mixtures containing strontium nitrate as an oxidant have been proposed (US 4 693 2010) in order to avoid the use of heavy metals.

Although the use of both potassium dinitrobenzofuroxan (KDNBF) and diazodinitrophenol (DDNP) as energetic ingredients (US 4 693 201), is known, the use of KDNBF as the sole energetic ingredient results in primers that are inconsistent or insensitive in their performance.^' Although this problem can be partially overcome through the addition of tetrazene as a sensitiser to the KDNBF or DDNP mixture, the long term stability of the resulting mixtures is poor, leading to an explosives hazard.

Primer mixtures containing KDNBF, tetrazene and strontium nitrate are known. Such mixtures can be formed through either a wet or a dry mixing process. However, a disadvantage with this type of primer is that, in general they are frequently too energetic and cartridges containing these primer compositions often bum too rapidly upon ignition, which is undesirable.

Cartridges used for training munitions are preferably designed to mimic real-life situations as much as possible without the need for extensive safety measures. Such cartridges differ from those used in live ammunition principally in the energy at which the bullets are expelled from the muzzle of the gun. Live ammunition is typically expelled from the barrel of a gun at energies of over 60 ft lbs (81.35 joules) whereas the cartridges of training munitions are typically expelled at 4 ft lbs (5.43 joules). Thus, although it is known to use training cartridges containing both a primer and a propellant, the use of such cartridges is associated with relatively high energy and necessitates the use of bulky and expensive protective clothing, which means that training does not take place under realistic circumstances.

There are several types of training ammunition available. These include Live training ammunition, Live low energy training ammunition and Low energy man on man training ammunition. -A-

Live training ammunition is designed to allow shooting in areas and ranges in which the danger zone is below that of live combat ammunition. These products can still kill but their range is reduced.

Live low energy training ammunition is designed to further reduce the danger zone and risk of fatal injury. It also reduces the damage caused to training areas. These products are still dangerous and cannot be used man on man.

Low energy man on man training ammunition is designed to eliminate the risk of fatal and minor injury during firearms training. The training of man on man is the nearest and most realistic training for real life combat situations. The guns muzzle energy must be kept below 3 ft/lbs and the projectile velocity kept below 400 ft/sec if even minor injury [broken skin] is to be eliminated. Protective clothing is still worn to cover eyes, ears, face, throat and bare skin to further reduce the risk of minor injury such as bruising.

In order to obviate the need for extensive protective clothing in training exercises and to enhance the realism thereof, a double primer propellant free cartridge has been proposed. Such cartridges can be used in live ammunition but find particular application with training ammunition. Cartridges of this type are described in United Kingdom patent application number US 6 422 149. Such cartridges typically comprise a front primer positioned adjacent the bullet to be expelled from the cartridge and a rear primer positioned adjacent the rear end of the cartridge against which the firing pin impacts when the gun is fired. Impact of the firing pin on the rear primer results in ignition of the primer composition present therein and causes a ball (typically plastic or steel) to be driven at high energy against the front primer. Upon impact of the rear primer driven ball against the front primer, ignition of the front primer composition occurs and causes the bullet to be expelled from the barrel of the gun.

The choice of primer compositions used in both the front and rear primers will depend upon the application in which the cartridge is to be used. The primer compositions of the rear primers tend to be relatively energetic to ensure that despite the relatively low energy at which the firing pin impacts the rear primer, efficient ignition of the primer composition occurs and results in the ball being driven at relatively high energy against the front primer. Typically the rear primer provides energies of 10 to 30 ft lbs (13.56 to 40.67 Joules) upon ignition. If the cartridge is to be used for live low energy training ammunition, the priming composition of the front primer is also itself relatively energetic to ensure that the energy at which the bullet is expelled from the barrel of the gun is relatively high. Typically if a double primer propellant free cartridge is to be use for live low energy training ammunition, the front primer suitably provides energies of 5 to 10 ft lbs (6.8 to 13.6 Joules) upon ignition. If the cartridge is to be used for low energy man on man training ammunition, the priming composition of the front primer is less energetic to ensure that the muzzle energy of the bullet expelled does not exceed 3 ft lbs (4.08 Joules).

The use of the double primer propellant free cartridges described above has made it possible to better control muzzle velocities. Using known primer compositions (such as lead styphnate) muzzle velocities not exceeding 2ft/lbs (2.72 Joules) have been observed for Man Marker Rounds (MMR) and for Live Low Energy Reduced Range (LERR) ammunition the muzzle velocities not exceeding 8ft/lbs (10.87 Joules) have been achieved.

However, the use of primer mixtures containing lead styphnate as an energetic component, for example, in double primer propellant free cartridges frequently results in inconsistent and unpredictable results. It is not unusual for a double primer propellant free cartridge either to fail to fire the bullet out of the muzzle or to be expelled at a rate which greatly exceeds the desired muzzle velocities for training munitions due to the rapid and unpredictable burning of the lead styphnate.

There is, therefore, a need for a priming composition that is free of toxic heavy metals, provides consistent and controlled burning on ignition and is suitable for use in both live and training munitions, particularly in double primer propellant free cartridges.

The present invention addresses that need.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a primer composition comprising phosphorus and an oxidising agent. Depending upon the required energenicity of the primer further optional components may also be present. These additional components include one or more of a gritty filler, a starch and a binding agent.

The phosphorus is preferably red phosphorus rather than white or black phosphorus due to its greater stability and reduced toxicity compared to white phosphorus, for example. The phosphorus acts as an energetic agent and the amount of phosphorus present will depend upon a number of factors, which include the particle size of the phosphorus, the method used to initiate ignition of the primer compositions, including the force of impact, whether the primer composition is to be used in live or training ammunition and if it is to be used in a double primer propellant free cartridge, whether it is to be placed in the front or rear primer. The presence or absence of one or more additional components such as a gritty filler, a starch and a binding agent will also influence the amount of phosphorus present. If the composition is to be used in live ammunition or in the rear primer of a double primer propellant free cartridge, for a maximum particle size of 50 μm, the amount of phosphorus suitably comprises 1.1 to 10.0 % of the dry weight of the primer composition. Preferably the phosphorus comprises 4 to 8% of the dry weight of the composition, especially 6% of the dry weight of the composition. Under these conditions energies in the range 10 to 30 ft lbs (13.56 to 40.67 Joules) can be achieved upon ignition. If the particle size of the phosphorus is larger, a smaller amount of phosphorus may be required, depending upon the energies required from the primer and the method of impact. Given these requirements, it will be within the skill of a skilled person to determine the optimum amount of phosphorus required for any particular application. However, for a phosphorus particle size of 75 to 500μm, the amount of phosphorus suitably comprises 0.5 to 7.0 % of the dry weight of the composition, preferably 1,0 .to 6.0% by weight of the composition and especially 2.5% by weight of the composition.

If the composition is to be used in low energy man on man training ammunition, for example in the front primer of a double primer propellant free cartridge, the amount of phosphorus suitably comprises 0.25 to 5 % of the dry weight of the composition. Preferably the phosphorus comprises 0.5 to 3% of the dry weight of the composition, especially 0.5 to 1.0 % of the dry weight of the composition. Under these conditions energies in the range 1.5 to 3.5 ft lbs (2.03 to 4.74 Joules) can be achieved. Energy levels of 1.5 ft lbs (2.03 Joules) have been obtained with double primer propellant free cartridges using either 1.5% by weight of phosphorus having a particle size of 50μm and a steel ball or 2.0% by weight of phosphorus having a particle size of 50μm and a plastic ball. If the particle size of the phosphorus is larger, a smaller amount of phosphorus may be required, depending upon the energies required from the primer and the method of impact. Given these requirements, it will be within the skill of a skilled person to determine the optimum amount of phosphorus required for any particular application. The amount of phosphorus used in the primer compositions will also depend, in part, on the type and presence of any additional components. If a gritty filler is present, the amount of phosphorus required will be less. The amount of phosphorus will also depend upon the particle size of the gritty filler; as the particle size of the gritty filler increases less phosphorus, in general, is needed.

Since some of the further components such as starch or binding agent do in themselves increase the rate of burn and or the amount of gas provided by the primer composition, the amount of phosphorus used will also depend upon the presence and nature of these additional components. If a binding agent or a starch is present, less phosphorus will be required if these components do in themselves increase the rate of burn and or the amount of gas provided by the primer composition. The effect of the additional ingredients on the rate of burn of the primer compositions can be readily determined by comparing the burning properties of the compositions with and without the presence of the additional components and changing the amount of phosphorus present if necessary.

In general phosphorus having a particle size in the range 10 to 500 μm can be used in the preparation of the primer compositions of the present invention. It will be appreciated from the foregoing discussion that if the primer composition is to be used in training ammunition or in the front primer of a double primer propellant free cartridge (for use in live or training ammunition), particle sizes in the range 10 to 200 μm can be used, with particle sizes in the range 10 to 50 μm being preferred. If the primer composition is to be use in live ammunition or in the rear primer of a double primer propellant free cartridge (for use in live or training ammunition), particle sizes in the range 40 to 500 μm can be used, with particle sizes in the range 100 to 500 μm being preferred.

A stabiliser may also be present in the event that the components of the primer composition are found to degrade over a period of time. Potassium carbonate may suitably be used as a stabilising agent. A skilled person will be aware of other stabilising agents that may also be used.

The oxidising agent may be any oxidant that reacts with the other components of the primer composition upon ignition only. The oxidant must be sufficiently stable so that spontaneous ignition of percussion caps containing the primer mixture does not occur in storage. Suitable oxidants include nitrates, bromates, iodates, chlorates, perchlorates, peroxides and oxides. Typical oxidants include potassium chlorate, potassium perchlorate, ammonium chlorate, ammonium perchlorate, calcium chlorate and calcium perchlorate. The use of potassium chlorate is particularly preferred, since it has been found that its presence means that the activation energy required for ignition of a primer composition containing this oxidant is negligible.

The amount of oxidant present will depend upon whether the composition is to be used in live or training ammunition or in a front or a rear primer of a double primer propellant free cartridge. In addition, the amount of oxidant present will depend upon whether any additional components such as a gritty filler, a starch component or a binding agent are present. The oxidant suitably comprises 20.0 to 99.0% by weight of the primer composition if no gritty filler is present, preferably 40.0% to 99.0% of the dry weight of the composition and especially 97.00% by dry weight of the composition. In a particularly preferred embodiment of the first aspect of the invention, the composition comprises 97.00% of potassium chlorate of the dry weight of the composition and no gritty filler. Such compositions find particular application when used in a front primer for a double primer propellant free cartridge.

If the composition includes a gritty filler, the oxidant suitably comprises 20.0 to 60.0% by dry weight of the composition, preferably 40.0 to 60.0% by dry weight of the composition and especially 60.0% by weight of the dry weight of the composition. In a particularly preferred embodiment of the first aspect of the invention, the primer composition comprises 60.0% by weight of potassium chlorate and 29.5 to 33.0% by weight of a gritty filler. Such compositions find particular application use as a rear primer in a double primer propellant free cartridge.

The presence of a gritty filler prevents spontaneous explosion of the active ingredients of the primer and provides sufficient friction on ignition of the primer to ensure that controlled and efficient burning occurs. Examples of suitable fillers include ground stone, glass, talc, feldspar and silicates of feldspar diatomaceous earth minerals, iron oxides and magnesium carbonate. Mixtures of any number of these materials may also serve as suitable inert fillers. Preferably the ground stone has particles in the range 5 to 150μm.

The presence or otherwise of a gritty filler depends upon the desired muzzle velocities required and whether the compositions are to be used in live or training ammunition or in the front or rear primer of a double primer propellant free cartridge (for use in either live or training ammunition). If a composition is to be used in the manufacture of a primer for training purposes such as in the front primer of a double primer propellant free cartridge the composition will suitably either contain no filler at all or will typically contain a filler such that its amount and particle size result in a primer having an energy of 1.5 to 3.5 ft lbs (2.03 to 4.75 Joules) upon ignition.

If the composition is to be used in the manufacture of a primer for live ammunition or in the rear primer of a double primer propellant free cartridge (either for training purposes or otherwise) the composition will suitably contain inert fillers having larger particle sizes. Typically the inert fillers for use in such applications have particle sizes in the range 60 to 120μm. Where an inert filler is present, it suitably comprises 10.00 to 50.00% of the dry weight of the composition, preferably 25.00 to 35.00% of the dry weight of the composition, especially 29.50 to 33.00% of the dry weight of the composition. In a particularly preferred embodiment of -lithe first aspect of the invention, the inert filler comprises 29.5 to 33.00% of the dry weight of the composition of the primer composition.

A starch component may be included in the primer mixture to facilitate the controlled burning of the primer mixture on ignition and thus the controlled generation of gases associated with combustion. It will be appreciated that the rate of combustion of the primer mixture of the present invention depends to a large extent on the amount and the type of the starch component present. The starch component typically comprises between 0.025 and 10.00% by weight of the dry weight of the primer composition. Preferably the starch component comprises 0.75 to 5% by weight of the dry composition, especially 1.00 to 3.00% by weight of the dry composition. It will therefore be appreciated that the presence of a starch component is associated with a higher gas production compared to compositions in which none is present and that primer compositions containing starch will most suitably be used in either in live ammunition or in the rear primer of a double primer propellant free cartridge (either for training purposes or otherwise) where higher energies are required. Although compositions for use in training ammunition (including those used in the front primer of a double primer propellant free cartridge) may contain starch, the amount and type of starch present will depend upon the other components present and desired energenicity.

Suitable starch components include powders derived from sources such as paper, cellulose, corn, rice, wheat, potato, maize and barley. In general it is preferred that when a starch component is present in a composition, the ratio of starch to oxidant is of the order of 1:6. Particularly good results have been achieved through the use of cornflour. In a particularly preferred embodiment of the first aspect of the invention, the primer composition contains 0.025 to 10.00% of cornflour by dry weight of the composition, particularly 0.75 to 5% by dry weight of the composition and especially 0.50 to 4.00% by weight of the dry composition. For preferred compositions including cornflour the ratio of cornflour to potassium chlorate is 1:6. Such compositions find particular application as the rear primer of a double primer propellant free cartridge (either for training purposes or otherwise).

The primer composition of the first aspect of the invention preferably contains one or more binding agents, the presence of which facilitates the formation of the primer composition into a paste and its loading into percussion caps for subsequent insertion into a cartridge. Preferably the binder doesn't burn or requires a very high activation energy in order for burning to occur. Any suitable binding composition that facilitates the formation of a paste can be used, providing the storage stability of the composition is not compromised. Examples of suitable binding compositions include latex emulsions such as BAL, shellac,, resins, glues, lacquers or any of the polysaccharides (such as gels or gums) used for setting or thickening purposes within the food industry or used as adhesives. Synthetic vinyl based polymers can also be used as can wall paper paste. Gelatines, alginates, celluloses, amyloses and other polysaccharides having the desired properties to facilitate the formation of a paste are known to a person skilled in the art. However, preferably the binding agent is a wall paper paste comprising carboxymethylcellulose and sodium hydroxymethylcellulose that has optionally been formaldehyde treated. Preferably the wall paper paste comprises 0.25 to 0.90% of the dry weight of the composition, especially 0.50% of the dry weight of the composition.

In a most preferred embodiment of the first aspect of the invention, the primer composition comprises 6.00% red phosphorus, 60.00% potassium chlorate; 29.5 to 33% inert filler, 0.50 to 4.00% cornflour and 0.5% of wallpaper paste by dry weight of the composition. This composition is suitably used in live ammunition or in the rear primer of a double primer propellant free cartridge (for either live or training purposes).

In a further preferred embodiment of the first aspect of the invention, the primer composition comprises 2.00% by weight red phosphorus, 97.00% by weight potassium chlorate, 0.50% by weight of a wallpaper paste and 0.50% by weight of BAL latex binder. All weights are quoted with reference to the dry weight of the composition. This composition is suitably used in training ammunition, particularly in the front primer of a double primer propellant free cartridge.

It is known that primer compositions can be prepared through the use of either wet mixing or dry mixing techniques. Wet mixing techniques have been found to produce the most homogeneous products but require the use of a drying step. It will be appreciated, however, that the drying of a bulk volume of a primer composition is inherently associated with the risk of explosion. Although dry mixing techniques can be used in the production of primer compositions, the technique is less suited for the production of bulk quantities of the primer composition and the homogeneity of the resulting compositions, generally, is not as good as that achieved through the use of wet mixing techniques.

The compositions of the present invention are, therefore, preferably prepared through the use of a wet mixing technique and a second aspect of the invention provides a method for the preparation of the primer compositions according to the first aspect of the invention. Typically the wet mix comprises 25g of water per lOOg of dry ingredients. To prevent the risk of explosion, the red phosphorus and oxidant are only mixed together in the presence of water.

For the preparation of a composition suitable for use in a front primer of a double primer propellant free cartridge, phosphorus is firstly added to water and thoroughly mixed. Potassium chlorate is then thoroughly incorporated into the mixture and finally the binder (BAL and/or wallpaper paste) is added. The resulting paste is then loaded into primer caps and dried in a drying oven. Potassium carbonate may be added to the mixture to improve its long term stability in the event that the stability of the dry composition is less than optimal. For the preparation of a composition suitable for use in live ammunition or in a rear primer of a double primer propellant free cartridge water is added to a dry mixture of red phosphorus, inert filler and the starch component. The oxidising agent is then added to the wet mixture and thoroughly combined therewith. Finally the binding agent is added to the mixture which results in the formation of a workable paste. The resultant paste is then metered into suitable containers for each application and then dried.

In a preferred embodiment of the second aspect of the invention, water is added to a dry mixture of red phosphorus, inert filler and cornflour to give a liquid slurry. Potassium chlorate is then added to the liquid slurry and mixed thoroughly. Wall paper paste is then added to the resulting mixture to give a paste, which can be readily loaded into the percussion caps used in cartridges.

The compositions are preferably dried at a temperature of between 60⁰C and 100⁰C. If it is desired to dry at 100⁰C, it is preferably to include a BAL latex binder in the composition to prevent shrinkage of the dry composition away from the wall of the cup. Drying at 6O⁰C results in less shrinkage.

It has been found that the primer composition of the present invention reacts with the brass cups typically used in the manufacture of percussion caps and that stainless steel caps should be used instead. A third aspect of the invention provides a percussion cap for use in ammunition comprising a stainless steel cap containing the primer composition according to the first aspect of the invention.

In a further development of the invention, it has now been recognised by the inventor that the primers of the invention, when wet mixed, can be safely incorporated directly into a cartridge casing without need for primer cups. In another aspect, therefore, the present invention provides a cartridge comprising an anterior portion and a posterior portion the posterior portion comprising a piston slideable in a case which case extends rearwardiy from the anterior portion, the piston including a hollow interior and the case defining an expansion chamber with which the hollow interior of the piston connects and characterised by a deposit of primer packed directly into the hollow interior at a position most distal to the anterior portion, the primer comprising red phosphorus and an oxidising agent.

Optionally, the anterior portion is provided with a gas passage which communicates with the expansion chamber, the gas passage being plugged by a deposit of primer, the anterior primer comprising red phosphorus and an oxidising agent. Again, there is no necessity for the primer to be encased in a primer cup.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will now be described with reference to the following non- limiting examples. Variations on these examples falling within the scope of the present invention will be apparent to a person skilled in the art.

Example 1

A primer composition was prepared by adding 36 g of water to a dry mixture containing 6g of red phosphorus, 33g of inert filler and 0.5g of cornflour. 6Og of potassium chlorate was added to the wet mixture and thoroughly combined. 0.5g of wallpaper paste was added to the resulting mixture and stirred until a paste-like consistency was achieved (15 - 30 seconds). The resultant paste-like mixture was metered into a stainless steel cups and placed in a drying oven.

The use of the percussion caps of example 1 in training ammunition resulted in an impact energy of the cartridge projectile of 3 ft/lbs or less. Example 2

A primer composition was prepared by adding 36g of water to a dry mixture containing 6g of red phosphorus, 32.5g of inert filler and 1.Og of cornflour. 6Og of potassium chlorate was added to the wet mixture and thoroughly combined. 0.5g of wallpaper paste was added to the resulting mixture and stirred until a paste-like consistency was achieved (15 - 30 seconds). The resultant paste-like mixture was metered into a stainless steel cup and placed in a drying oven.

Example 3

A primer composition was prepared by adding 36g of water to a dry mixture containing 6g of red phosphorus, 32.75g of inert filler and 0.75g of cornflour. 6Og of potassium chlorate was added to the wet mixture and thoroughly combined. 0.5g of wallpaper paste was added to the resulting mixture and stirred until a paste-like consistency was achieved (15 - 30 seconds). The resultant paste-like mixture was metered into a stainless steel cup and placed in a drying oven.

Example 4

A primer composition was prepared by adding 36g of water to a dry mixture containing 6g of red phosphorus, 30.5g of inert filler and 3.Og of cornflour. 6Og of potassium chlorate was added to the wet mixture and thoroughly combined. 0.5g of wallpaper paste was added to the resulting mixture and stirred until a paste-like consistency was achieved (how long does this take - approximately?). The resultant paste-like mixture was pressed into rimfire primer cases using a small press at 30 psi with an angled punch and placed in a drying oven.

This product was able to cycle the M16 and the G36 OK over repeated rounds of ammunition. Example 5

A primer composition was prepared by adding 36g of water to a dry mixture containing 6g of red phosphorus, 29.5g of inert filler and 4.Og of cornflour. 6Og of potassium chlorate was added to the wet mixture and thoroughly combined. 0.5g of wallpaper paste was added to the resulting mixture and stirred until a paste-like consistency was achieved (15 - 30 seconds}. The resultant paste-like mixture was pressed into a stainless steel cup and the cup and primer dried.

Example 6

The following preferred primer compositions have been successfully and safely incorporated directly into cartridge cases without the use of primer cups and the cartridges have performed satisfactorily in tests. The tested cartridges were double primer cartridges and incorporated both an anterior and posterior primer having the compositions as listed below.

For each primer, a paste was formed from the dry ingredients (10Og) by adding to water (35g) in the order PVA, red phosphorous, corn flour (where present), inert filler, potassium chlorate, wallpaper paste and mixing thoroughly after the addition of each component. The resulting pastes were deposited directly into the casing of a double primer cartridge and then dried at around 60⁰C.

Once cured, assembly of the cartridges was completed and the cartridges fired from conventional weapons.

Claims

1. A primer composition comprising red phosphorus and an oxidising agent.

2. A primer composition according to claim 1, which also comprises one or more components selected from a gritty filler, a starch and a binding agent.

3. A primer composition according to claim 1 or claim 2, wherein the phosphorus comprises 0.25 to 10.00%, particularly 0.50 to 8.00% and especially 1.50 to 6.00% of the dry weight of the composition.

4. A primer composition according to any one of the preceding claims, wherein the oxidising agent is selected from one or more of potassium chlorate, potassium perchlorate, ammonium chlorate, ammonium perchlorate, calcium chlorate and calcium perchlorate.

5. A primer composition according to claim 4, wherein the oxidising agent comprises 20.00 to 99.00%, especially 60.00 to 97.00% of the dry weight of the composition.

6. A composition according to claim 4 or claim 5, wherein the oxidising agent is potassium chlorate.

7. A primer composition according to any one of the preceding claims wherein the inert filler is selected from ground stone, ground glass, talc, feldspar, and silicate minerals of diatomaceous earth elements having a particle size in the range 5 to 150μm.

8. A primer according to claim 7, wherein the inert filler comprises 10.00 to 50.00%, preferably 25.00 to 35.00% and especially 29.5 to 33.00% of the dry weight of the composition.

9. A primer according to claim 8, wherein the inert filler is ground stone.

10. A primer according to any one of the preceding claim^'s, wherein the starch component is selected from one or more of powders derived from paper, cellulose, com, wheat, potato, rice, maize and barley.

11. A primer according to claim 10, wherein the starch component is cornflour.

12. A primer according to claim 10 or claim 11, wherein the starch component comprises 0.025 to 10.00%, preferably 0.75 to 5% and especially 1.00 to 4.00% by weight of the dry weight of the composition.

13. A primer composition according to any one of claims 10 to 12, wherein the ratio of the starch component to the oxidant is 1:6.

14. A primer composition according to any one of the preceding claims, a binding agent selected from BAL latex binder or a wallpaper paste comprising carboxymethylcellulose and sodium hydroxyethylcellulose.

15. A primer according to any one of the preceding claims comprising 6.00% of red phosphorus, 60.00% of potassium chlorate, 29.50 to 33.00% of an inert filler, 0.50 to 4.00% of cornflour and 0.5.0% of wallpaper paste by dry weight of the composition.

16. A primer according to any one of claims 1 to 14 comprising 2.00% of red phosphorus, 97.00% of potassium chlorate, 0.50% of wallpaper paste and 0.50% of a BAL latex binder by dry weight of the composition.

17. A primer as claimed in claim 1 comprising 7% red phosphorous, 70% potassium chlorate, 5% starch, 1% binding agent and 17% inert filler.

18. A primer as claimed in claim 1 comprising 7.9% red phosphorous, 47.4% potassium chlorate, 1.4 % binding agent and 43.3% inert filler.

19. A primer as claimed in claim 17 or 18 wherein the inert filler comprises a mixture containing feldspar, diatomaceous earth, oxides of iron and magnesium carbonate.

20. A primer as claimed in any of claims 17 to 19 wherein the red phosphorous has an average particle size of between 15 and 20 μm, preferably 18 μm.

21. A method of preparing a primer according to any one of the preceding claims comprising the steps of

a. combining water in an amount of 36% of the final weight of the dry composition to a mixture of phosphorus, inert filler and starch component;

b. adding the oxidising agent to the wet mixture and thoroughly combining the resulting mixture of components; and

c. adding the binding agent to the mixture obtained from (b) thereby to give a paste suitable for placement in a cup of a percussion cap.

22. A percussion cap comprising a stainless steel cup and a primer composition according to any one of claims 1 to 20.

23. An ammunition cartridge comprising one or more percussion caps according to claim 22.

24. An ammunition cartridge according to claim 23 which is a double primer propellant free cartridge.

25. An ammunition cartridge according to claim 23 or 24 which further comprises a propellant.

26. A cartridge comprising an anterior portion and a posterior portion the posterior portion comprising a piston slideable in a case which case extends rearwardly from the anterior portion, the piston including a hollow interior and the case defining an expansion chamber with which the hollow interior of the piston connects and characterised by a deposit of primer packed directly into the hollow interior at a position most distal to the anterior portion, the primer comprising a composition according to any one of claims 17.

27. A cartridge as claimed in claim 26 wherein the anterior portion is provided with a gas passage which communicates with the expansion chamber, the gas passage being plugged by a deposit of primer, the anterior primer comprising a composition according to claim 18.