EP2633263A2

EP2633263A2 - A method of bonding cores and jackets of bullets designed for special applications

Info

Publication number: EP2633263A2
Application number: EP11813862.7A
Authority: EP
Inventors: Jirí NESVEDA; Ladislav BENÁCAN; Jaroslav Vadkerti; Stanislav Sysel; Jirí JANOUS
Original assignee: Sellier and Bellot AS
Current assignee: Sellier and Bellot AS
Priority date: 2010-10-27
Filing date: 2011-10-26
Publication date: 2013-09-04
Also published as: CZ2010783A3; WO2012055381A2; CZ306513B6; WO2012055381A3

Abstract

The solution according to the invention consists in a method of bonding cores and jackets of bullets where the solder and at the same time the base material forming the bullet core are lead alloys or pure Pb and the suitable non-corrosive flux is a gum rosin type flux or some solid organic acids, both in the mixture with gum rosin and alone, applied in powdered state onto the bullet cores using a specifically developed technology. The bonding of the both bullet parts is non-corrosive and its strength is fully comparable to all the other bonding methods. No significant adverse effect on the working or living environment occurs in the series production. The method is suitable for mass production of a variety of types and calibres of jacketed bullets, which are designed for loading into all sorts of hunting ammunition and civilian ammunition designed for special applications.

Description

A Method of Bonding Cores and Jackets of Bullets Designed for Special Applications Field of the Invention

The invention applies to the method of bonding cores and jackets of bullets of a variety of types and calibres of hunting rifle ammunition and ammunition for special civilian applications.

Background of the Invention

Ever since about 18 century, generations of researchers in the field of ballistics as well as practical shooters have beeri dealing" in determining ^ principles of bullet effects on living organisms - i.e. humans and animals. Throughout the time, a number of theories concerning bullet effects on a living organism came into existence. One of the examples is the erroneous view of the bullet's stopping power resulting from its "knockout index", which is a result of transferring the bullet momentum to a human or animal body. This theory was perfected in 1930's and the RSP - Relative Stopping Power was determined, expressed mathematically as a product of the bullet mass, velocity, cross-section and shape factor. Another effectiveness criterion defined around the same time is based on the bullet energy, and StP - Stopping Power was expressed as a product of the bullet impact energy, cross section and shape factor. However, neither the bullet momentum nor its energy can serve as a measure of the bullet effect on an organism. Bullet "effectiveness" has to be defined, which is the effective potential that should be understood as a capacity for "effect", which might or might not occur. The interaction of the bullet and target must be taken into account when evaluating the effects. Weigel, a German ballistician, was the first person to use the volume of the channel produced by firing into simulant as a measure of the effectiveness. In the USA, a new effectiveness criterion was defined in 1970's - RII - Relative Incapacitation Index, which gave rise to a number of disputes. The French experts Caranta and Legrain focused on practical shooting into wet clay; however, this simulant differs considerably from the living tissue due to its heterogeneous nature. The American expert Matunas published his own criterion - PIR - Power Index Rating, expressed by a product of energy, energy transfer coefficient and diameter value, dividing the well-known calibres from 5.06 to 12.69 mm into six groups. In 1970's, an attempt to finally resolve this issue was made in the USA. It involved both practical firing into a newly selected simulant - gelatine, which resembles most the living tissue, and creation of a complex computer model of a human body with organs divided into zones according to their vulnerability, VI - Vulnerability Index. However, neither this method nor the method based on examination of real cases of firearm uses - "street results" - produced the expected results, due to excessive spread of the values.

It ensues from the above-said that even the most perfect computer models are not able to take into account some other factors, such as physical and mental state of the victim, actual situation in the combat area or the crime scene, etc. In spite of that, the known types of bullets can be categorized roughly into several basic groups in terms of their wounding effect: the bullets with the smallest wounding effect are those that do not alter their direction as they

caliHrds Having the length-to-calibre ^'ratio^' i df 3 to 3v¼, which are Kabl tb the roih^ mothent as they pass through the tissue - they rotate and fragmentize, such as the feared bullets .223 Remington; used in¹ the^; ammunition ^;of ^'¾¾ ¹16 rifles in the Vietnam War, as Weil as^: all the

and special civilian applications. ^■ - ^{■■' , | ; s 1} ··^■ . ^ ^{; ;} - ^{; ¾} ^{i ;} In principle, there are three¹ t pes ' of bullets at present - military, hunting arid¹ civilian, including law enforcement arid spbrtirig bullets, in tens' of calibres and hutidreds of Variants. Different requirements are placed on each group of bullets - while hunting bullets have to be able to kill the game animal as quickly as possible, militar ^' bullets have to^disable the eneri y from combat with the maximum efficiency, at best until the end of the war conflict: Full- jacketed bullets, which comply with the requirements of the Haag Conference, leave clean penetration wounds in soft tissues. However, they do not meet the current demands on the wounding effect, and thus- maitiufactuf ers collectively switch to productiori of ammunition ldaded with the above-mentioned high-velocity bullets of small calibres, which also do not contradict the Haag Conference, aria* moreover they enhance the accuracy of fire in the fully automatic mode due to recoil reduction. The severity of crimes and increasing incidence of terrorist attacks have to be considered in case of civilian bullets designed for police forces, special units, etc. Here, it is necessary to eliminate the offender with maximum efficiency, arid thus disable the offender from continuation of criminal activity. At the same time, however, an unpredictable threat to the surroundings or injury of non-interested people present in the place of action must be avoided. One of the solutions is to use hollow point bullets, which exhibit controlled disintegration upon impact, causing extreme nerve shock and subsequent immediate disabling of the offender.

Firing into suitable simulants is conducted in order to evaluate the wounding effect. The measure of the wounding effect is as perfect as possible and highly reproducible bullet disintegration, when the bullet reshapes to resemble a "mushroom" - a process called mushrooming, along with the shape and depth of the wound channel. Gelatine and glycerine soap are exclusively used as simulants. Transparency is an advantage of gelatine while elasticity is its disadvantage as; it disables more specific determination of the course of the bullet energy transfer during me penetration, for the wounc? channel closes. It is vice versa in case of glycerine soap. , f < _;

The design of jacketed bullets, which have been used for over 100 years, is generally known and is based on encasing the core made of lead or lead alloys into a jacket made most commonly of brass, tombac or so called tombac plate. The encasing is performed mechanically by pressing the core into the jacket and subsequently by securing the core to prevent it from dropping out, e.g. by hemming. In some special bullets where emphasis is placed on the maximum reduction of harmful product emissions, lead vapours, the bullet rear part is jacketed as well. If hollow cavities are formed in these bullets, which bullets are designated as HP - hollow point bullets, an undesirable phenomenon occurs as these bullets pass through the tissue or simulant. By virtue of a significantly higher inertial mass, the core separates from the jacket, which can be accompanied also by fragmentation of both components. As a result, undesirable dispersion of the bullet energy occurs. Ammunition manufacturers have been dealing with this problem for about past 15 years. Several; basic technical solutions are available - gluing, soldering or electroplating. The general; term "bonding" has come into use in the military industry for all these joining methods.

Extensive gluing tests conducted for instance by a Brazilian company CBC with the Use of top quality Loctite type curable adhesives did not bring positive results. The probable cause is insufficient impact strength of joints. Electroplating, which was applied for instance in the Gold Dot bullet, requires special equipment and the method is demanding in technical and financial terms, because an extremely powerful equipment is required for applying metal layers having the thickness in the order of several tenths of mm. Therefore, soldering appears to be the most promising method of joining the bullet cores and jackets.

Soldering is one of the oldest and at the same time most efficient methods of joining two identical or different metal materials - called base materials, with the use of another metal - solder, whose composition can be significantly different from the base material, unlike welding. A joint strength that is close to the base material strength can be achieved by appropriately selecting the base material and solder composition and by optimizing soldering conditions. Both physical-chemical and metallurgical processes can operate in soldering, which processes involve for instance the solder material diffusion into the base material and vice versa, mutual dissolution of both materials resulting in formation of solid solutions, or even reactions of both materials that produce intermetallic compounds. A sufficient solder adhesion to the base material as well as the solder spread factor and capillarity ; are a prerequisite of solderability bf both rnaterials. Applicable solders include both pure metals, whose range of choice for soldering up to 450 °C is considerably limited to metals with 'a very low melting point such as Bi or Sn, and tens of known alloys of Pb/Sn/Bi/Sb/Ag etc.

Every substance in melted state tends to protect itself against operation of external forces by means of its cohesion forces - surface tension, and therefore it assumes the shape of a solid having the least surface area', which is a sphere. If these forces are overridden by adhesion forces in interaction with another substance, both materials can be considered as sol ferable and the degree of solderability can be determined by measuring the angle between the solder surface and the base material in the point of contact. Solderability of two pure metals can be easily estimated from binary¹ equilibrium diagrams, where three basic cases may occur - the metals are absolutely non-wettable, or the metals form interrnetallic compounds, or the metals form eutectic, which is the optirnum precondition for solderability. From this point of view, Pb has to be considered as non-soldefable in respect of Cu and Zn or Cu/Zn alloys.

Solderability can of course be significantly enhanced by alloying with other metals, tens of types of "lead" solders are known today, and particularly by using flux, which is necessary in all cases when soldering is conducted without protective atmosphere. The main functions of flux include elimination of metal oxides, considerable reduction of solder surface tension, and thus increasing the solder wettability and spread factor and protection of soldered joint against further oxidation. Theoretically, any inorganic or organic compound that is able to dissolve the microscopic layer of oxides sufficiently quickly can serve as flux. These are inorganic, hon-oxidizing acidis, most commonly HCI, inorganic halide salts ZnCl₂, SnCl₂, organic halide compounds - aniline, hydrazine and diethylamine hydrochlorides" etc;, arid further a numerous group of organic acids, the most known and most efficient of whom is the natural mixture of abietic acid and dextropimaric acid, obtained as a distillation residue from distillation of pine resin and known under the designation of gum rosin or "colofony". \ All fluxes can then be divided into two basic groups: corrosive, including all halogen compounds - chlorides, and non-corrosive - organic acids.

If we generally designate a divalent metal as Me (metal) and the oxide thereof as MeO, then the oxide dissolution mechanism can be expressed by simple equations:

2 HC1 + MeO = MeCl₂ + H₂0 ' ' ^■"

ZnC12 + MeO = MeCl₂ + ZnO

If we generally express a monobasic organic acid by a formula RCOOH, where R is an organic residue, the oxide dissolution by organic acids can be described by the following equations: ^{■ ■ "!}!^{^ " ' " ' '}

2 RCOOH + MeO = (RCOO)₂ Me + H₂0. j

An analogous equation can be us for dibasic or gafti^ · R(COOH)₂ + MeO = (RCOO)₂Mc + H₂0 i

The above-said equations suggest that if highly corrosive halogen compounds, including organic compounds which remove HC1 by thermal decomposition, are used as flux, a metal chloride will always be the product; in case of soldering, Cu - CuCl₂ will be the product, which is a hygroscopic corhpound exhibiting a strongly acidic reaction by influence of hydrolysis: ^{! '}

CuCl₂ + 2 H₂0 = 2 HC1 + Cu(OH)₂.

The initial ZnCl₂ reacts in a similar fashion. If these- compounds cannot be quantitatively eliminated from the joint, they can cause the joint corrosion, and thus deterioration; of its mechanical properties. Therefore, corrosive fluxes are not recommended for soldering deep or capillary joints. To the contrary; e:g. Cu or Zn salts o organic acids, such as gum rosihs, are non-hygroscopic, insoluble and non-corrosive compounds.

When using highly corrosive and toxic fluxes based on ZnCl₂ + HC1, ZnCl₂ + NH₄C1 + HC1, where the melting point of ZnCl₂ is decreased by addition of salmiac through the formation of eutectic at T 186°C, or when using similar mixtures, with addition of organic chloro compounds in the form of solutions, pastes or gels, then gaseous HC1, hydrochloric acid vapours, free Cl₂, the vapours of NH₄C1 subliming at 350 °C as well as ZnCl₂ vapours liberate in the soldering process. In mass production, this represents not only a burden on the environment but it places extreme demands on occupational hygiene and safety. Workers must use special protective devices, the manufacturing plants must be equipped with efficient exhaustion with an absorber arid all the equipment, tools and instruments must be made of acid-resistant materials. Considering the extreme toxicity of these compounds to all aquatic organisms, any dropping must be collected in special pits or acid sewer and waste water disposal must be addressed.

Despite the indisputable benefits of using the non-corrosive fluxes of the gum rosin type, which is a non-toxic compound, inert in the solid state and qualified as an irritant only according to the most recent categorization, which means that a standard type of gloves and a respirator suffice for protection, the ' ammunition manufacturers involved in the "bonding" process use exclusively ZnCl₂ based corrosive fluxes; This can be caused by a lack of mastery or lack of knowledge of the technology of applying powdered fluxes in mass production compared to the seemingly simple technology of using solutions or suspensions of the said highly corrosive and toxic compounds. ;

Disclosure of the Invention ¹ -

The solution according to the invention describes a simple and very efficient bullet soldering technology, using a specifically developed method of application of non-toxic powder gum ri>sin type fluxes, which method is incomparably friendlier to the environment and places only minimum demands on the occupational hygiene and safety; The modification of the soldering process lies in the fact that during this process joining of two base materials with conventional solder does take place. But joining two base materials with a conventional solder instead it involves joining only two materials of which one fulfils the role of the solder and base rriaterial proceeds at the same time. The said material is the proper bullet core, which must meet three essential requirements for this purpose:

1. Its density must be as close as possible to the density of pure Pb;

2. It must exhibit as high flowability as possible in the melted state to ensure efficient degassing; ¹ -

3. A sufficiently strong bonding ,with the jacket material must occur with the help of a suitable flux even if the said bonding is an adhesion joint only, i.e. a joint where the other above- mentioned metallurgical phenomena have not been applied. I Three basic types of materials can thus be applied, i.e. piire metal Pb, eutectic alloys having the least possible content of the alloying agent - Pb / Ag 2.5 % or alloys of very close composition - Pb / Ag 0.3 - 215 ⁶λ, and non-eutectic alloys having a composition close to pure metals - Pb / Sn 0.1 - 7 %, where the amount of Sn of approximately 7 % proved to^: be the limit amount in terms of undesirable increase in hardness and decrease in flow. According to the equilibrium diagram of Pb/Sn alloy, higher contents of Sn occur in the extended area of so called slush state between liquid and solid. Pb/Sb alloys, which are frequently us6d for production of Pb bullets or cores, are not too suitable for soldering purposes, except for very small amounts of Sb, for the reason of the capacity of Sb to form brittle intermetallic compounds with Zn in the bullet jacket.

The above-mentioned metal materials were processed in the standard fashion, by drawing a wire of a suitable diameter, of which wire cores were manufactured, the weight of the cores being such that a bullet of the specified weight category is formed together with the jacket. Extensive testing conducted by the development department of our company proved clearly that the above-mentioned materials including pure Pb can be bonded, with the use of a suitable non-corrosive gum rosin t^e fiujc applied on bullet cores using the method according to the : invention, to jacket' by ^¾ Jttini^' Of^' s^:uch'-^{; ''}strength that the bullets subsequently manufactured from the semi-finished products fabricated in such fashion meet all the specified tests. " ^{' ;:}\ ^""; ^: · ^{■ ' <} - ^{■■■ ■ '} ,^:

Flux application is performed by the method according' to the invention in rotating drums made' bf any material, but best made of a metal material, resistant to the temperatures of up to approximately 300°C. The drams a e bf a cylindrical shape with smooth inner surface and they are riot fitted with any inner partitions or projections. The cores, preheated to the temperature of approximately 200 - 250°C, are poured into the rotating drum and a calculated dose of powder flux is immediately added. The flux particles adhere to and melt on the surface of the cores and form a thin uniform layer on the cores by influence of the drum rotation. If the optimum inclination and rotation speed aire set, the cores cool down belbw the flux melting point within several minutes, depending on the thermal capacity of the batch and the drum thermal conductivity, arid the cores can be poured onto a metal sieve, where t ey are spread and left to cool down to the ambient temperature.

Applicable fluxes include Various types of gum rbsin, including its hydrogenated or polymerized form, as well as sorne kinds of solid organic acids, both in the mixture with gum rbsin and alone. These compounds must meet several fundamental conditions: th melting point should range from 100 to 250 °C and the melting must not be accompanied by decomposition to toxic products or by decarboxylation. If a mixture of two or more substances is used, their melting points should be as close as possible and the constituents must not exhibit any adverse reaction in the melted state. Some of aliphatic saturated dicarboxylic acids such as gtataric acid, adipic acid, pimelic acid, azelaic acid, sebacib acid etc. can be recommended from organic acids. !

The cores that have been coated with a suitable flux in this fashion are subsequently mechanically loaded into the bullet jackets, whereby the semi-finished product is ready for soldering. As the resin layer on the core acts as a sealantj the cores are, after having been

^'. : · ^{" ■ ■} - ^'-^{' ■}, ^'. · · . ί loaded into the jackets, sufficiently fixed and thus protected against dropping out without it being necessary to apply pressing under higher pressures. However, a sufficient gap is formed between the jacket and the core to allow escape of gaseous products originating in the soldering process, whereby undesirable melt ejection or ejection of partially melted cores is prevented. Also, these semi-finished products can be stored in any position prior to soldering, which is impossible in the technology using liquid fluxes.

The proper soldering can' be performed by standard methods, for instance in preheated metal blocks, in electric furnaces, using electromagnetic induction, etc. After soldering pure Pb cores, a regular conical shape of the core is formed¹ by influence of high shrinkage of Pb, which shape serves as a visual proof of a perfect soldered joint. Due to the extremely low hardness of unalloyed Pb, bullets having these cores exhibit maximum disintegration - "mushrooming". By adding any of the above-mentioned alloying agents, which increase alloy hardness and strength, the process of the bullet controlled disintegration can be regulated in a wide range. ¹ · _¾

Soldering is followed by the firial mounting of the bullet into the cartridge using known mechanical methods. ^! "

Examples

In an applying drum, comprisin a steel cylindrical vessel having the volume of 5 1, driven by an electric motor through a transmission mechanism* having a speed control option and inclination angle adjustment option and equipped with a dumping mechanism, an inclination angle of approximately 30 ° and rotation speed of approximately 60 rpm are set. In the course of the rotation, 200 - 300 cores for manufacture of 9 mm Luger JHP bullets are poured into the drum, which cores are preheated to approximately 200°C, and a calculated dose of rosin gum powder flux is immediately added so that the consumption is approximately 2.5 - 3 mg per 1 square centimetre of the surface area, that is 2 - 2.5 g per 200 cores. Uniform wetting of all cores with the melted flux occurs immediately. Within several seconds, the batch temperature decreases to such value that the flux adhesion to the cores is enhanced, and the cores start mix up in the drum rotation direction. This phase lasts for several minutes and depends on the thermal conductivity and thermal capacity of both the drum and the batch. Pb alloys have different thermal conductivity and specific heat. As soon as the adhesion of the cooling down flux increases to the value when the cores, start to conglomerate, the operation is interrupted and the cores are poured, onto a prepared metal sieve, where they are uniformly spread and left to cool down to the ambient temperature. After cooling down, the cores are ready for the subsequent, above-said operations.

Industrial application

The solution according to present invention can be utilized for mass production of a variety of types and calibres of jacketed bullets, which are suitable for loading into all sorts of hunting ammunition and civilian ammunition designed for special applications.

Claims

1. A method of bonding cores and jackets of bullets designed for special applications characterized in that it is performed by soldering technology, where the spider and at the same time the base material forming the bullet core are lead alloys or pure Pb and the suitable non-corrosive flux is a gum rosin type flux and/or some of the types of solid organic acids, both in the mixture with gum rosin and alone, applied in powder state onto the bullet cores using a specifically developed technology.

2. A method of bonding cores and jackets of bullets according to the Claim 1 characterized in that the solder and at the same time the base material of the i j bullet cores are eutectic alloys having the least possible content of the alloying agent, Pb/Ag 2.5 %, or alloys of very close composition Pb/Ag 0.3 - 2.5 %.

3. A method of bonding _; cores;^, and jackets of bullets according to the Claim _: 1 c h a r a c t e r i z e d i n t h a t the. solder and at the same time the base material of, the bullet; cores are non-eutectic alloys having the, composition close to pure , metals Pb/Sn O.l -7.0%. ^^,, ;ι,¾_: ^. _ι; ^' v li j-c _:i .^ ah,,,..:. .:;.,>!:, .= γ. π ; yi;i<;. · .

4. A method of bonding cores and jackets of bullets according to the Claim 1

ch aractcri zed in t hat the spider and at the same time the base material of the i

• i bullet cores is, with an advantage, pure Pb. j , _ai . ; ._;

5. A method according to the Claim 1 char a c t e r.i z e d, in that suitable non-corrosive fluxes of gum rosin type have been selected from the group of solid organic acids, both alone and in mixtures. , . ₅ J :y;;k

6. A method according to the Claim 5 ch aracter i z e d in t h a t the flux from the group of saturated dicarboxylic acids are glutaric acid, adipic acid, pimelic acid, azelaic acid and sebacic acid.

7. A method according to the, Claim 5 h a r a c t e r i ze d in t h a t a mixture of abietic acid and dextropimaric acid, known under the designation of gum rosin, including its hydrogenated or polymerized form, is used as a flux, with an advantage.

8. A method according to the Claim 1 characterized in that coating of the preheated bullet cores with powder flux is performed using" a specifically developed technology in cylindrically shaped rotating drums having a smooth inner surface.

9. A method according to the Claim 8 c h a r a c t e r i z e d in that the bullet, cores, preheated to the temperature of approximately 200 - 250°C, are poured into the rotating drum and a precisely weighted dose of powdered flux is immediately added, the flux particles adhere to and melt on the surface of the cores and, if the optimum inclination and rotation speed of the drum are set, the flux particles form a thin uniform and continuous layer on the cores.

10. A method according to the Claim 5 c h a r a c t e r i z e d in that the suitable fluxes selected from the group of sqhd organic acids guarantee non-corrosivity of joints and protect the joints against further corrosion.,

11. A method according to the Claim I characte i_;z e d in that it is applicable for mass production of a variety of ; types and calibres of jacketed bullets, which are suitable for loading into all sorts of hunting ammunition and civilian ammunition designed for special applications.

12. A method according to the Claim 1 characterized in that no significant burden on the working or living environment occurs in the series production of bullets.