Cartridge with an embedded deflagrating explosive cord for propellant ignition

Abstract

The present disclosure relates to a cartridge (100) comprising a casing (110) arranged to house a propellant (120), a propellant ignition system (101) and at least part of a projectile (180); the propellant (120) arranged to, upon ignition, generate gas and heat in the casing (110), thereby applying force to the projectile (180); the propellant ignition system (101) comprising a rapid deflagration cord (140), RDC, wherein the RDC (140) extends through the propellant (120) and is arranged to, upon ignition, undergo deflagration and inject high temperature particles and / or gas into the propellant (120), thereby igniting at least part of the propellant (120) around the RDC (140); and the projectile (180) arranged to be launched from the cartridge (100) upon ignition of the propellant (120).

Description

[0001] Cartridge with an embedded deflagrating explosive cord for propellant ignition

[0002] TECHNICAL FIELD

[0003] Ammunition, cartridges, propellant ignition, rapid deflagration cords, propellant igniters, detonators, primers, and casing base plate design.

[0004] BACKGROUND

[0005] Cartridges are self-contained units of ammunition that consist of a projectile or bullet, a propellant, and a casing that holds them together. The design of cartridges varies depending on the weapon system they are used in. For example, the Carl Gustaf anti-tank weapon fires an 84 x 245 mm rimmed recoilless, 84x245R RCL, cartridge with a blowout base for propellant gas ventilation. The cartridge is recoilless, single-shot, breech-loaded, and laterally percussion fired.

[0006] Artillery pieces use a variety of cartridges depending on the calibre of the gun. For example, the M109A6 Paladin self-propelled howitzer uses a 155mm M107 high-explosive projectile that is loaded into a brass cartridge casing filled with propellant. The propellant is ignited by an igniter arranged at the base of the cartridge.

[0007] The initiator in a cartridge performs a critical step in the firing process. An initiator, such as a detonator, is typically located at the base of the cartridge and contains a small amount of impactsensitive explosive that is designed to activate the igniter, for example when struck by the firing pin. The initiator may then ignite an igniter that in turn ignites the propellant, which burns rapidly and produces hot gases that expands and applies pressure to the base of the projectile. For a cartridge in a weapon system, the forces generated by the burning propellant typically accelerates the projectile down a barrel of the weapon system. In small arms ammunition a primer typically serves as both the initiator and the igniter, whereas in larger cartridges the initiator and the igniter may be two components.

[0008] The techniques used to facilitate rapid propellant ignition use of an igniter comprising an explosive, such as a container housing explosive arranged to explode and burn adjacent propellant. The igniter needs to be designed to ignite the propellant reliably and consistently when the cartridge is activated, such as when struck by the firing pin. The propellant also needs to be formulated to burn completely and at a desired rate, producing an amount of gas that results in a desired pressure during the acceleration of the projectile. The shape and size of the propellant grains may also affect how the propellant burns and how much gas is produced.

[0009] There is a need to provide cartridges with improved propellant ignition and projectile ejection.

[0010] SUMMARY OF THE INVENTION

[0011] The invention relates to improving the design of cartridges by utilizing a rapid deflagration cord for propellant ignition.

[0012] One object of the invention is to provide a cartridge with improved propellant ignition by utilizing a propellant ignition system comprising a rapid deflagration cord.

[0013] This has in accordance with the present disclosure been achieved by means of a cartridge comprising:

[0014] - a casing arranged to house a propellant, a propellant ignition system and at least part of a projectile,

[0015] - the propellant arranged to, upon ignition, generate gas and heat in the casing, thereby applying force to the projectile,

[0016] - the propellant ignition system comprising a rapid deflagration cord, RDC, wherein the RDC paths through the propellant and is arranged to, upon ignition, undergo deflagration and inject high temperature particles and / or gas into the propellant, thereby igniting at least part of the propellant around the RDC, and

[0017] - the projectile arranged to be launched from the cartridge upon ignition of the propellant.

[0018] This has the advantage of allowing for an improved ignition of the propellant. This further allows more freedom in designing the cartridge, such as removing the space previously occupied by a traditional propellant ignition system, such as a container housing explosive, or to design the base plate of the casing without the restrictions of traditional propellant ignition systems with container housing explosive arranged at the base plate.

[0019] In some embodiments, the propellant ignition system comprises an initiator being arranged to, upon activation by external stimulation, ignite the RDC.

[0020] In some embodiments, the initiator comprises a detonator, an electro-explosive device, an electro- pyrotechnic initiator, a percussion primer, a blasting cap, or a length of RDC.

[0021] This has the advantage of allowing for a dedicated initiator arranged to ignite the RDC and may improve the reliability of the activation of the propellant ignition system compared to embodiments in which an external agent attempts to directly ignite the RDC. In some embodiments, the casing comprises a propellant support arranged to hold the propellant in position inside the casing.

[0022] This has the advantage of allowing for better control of the propellant and RDC position inside the casing, which leads to a more reliable ignition of propellant.

[0023] In some embodiments, the RDC comprises a metal sheath encasing the explosive material of the RDC.

[0024] This has the advantage of allowing for increased deflagration speeds along the RDC. This further has the advantage of allowing the ejection of particles and gas from the deflagrating RDC to be tailored based on the properties of the selected metal sheath.

[0025] In some embodiments, the casing comprises a cylindrical part that is sealed at one end by a base plate, and initially sealed by the projectile at the other end, wherein the base plate is arranged to break open and / or be ejected backwards upon ignition of the propellant.

[0026] This has the advantage of allowing for improved cartridge designs for recoilless rifles and other weapon systems where the base plate is arranged to undergo a process of breaking open or being ejected backwards.

[0027] In some embodiments, the propellant ignition system comprises the RDC and an auxiliary igniter, wherein the RDC is arranged to ignite the auxiliary igniter, and wherein the auxiliary igniter is arranged to, upon ignition, undergo deflagration and inject high temperature particles into the propellant, thereby igniting at least part of the propellant.

[0028] This has the advantage of allowing for the initial ignition of one RDC to spread in multiple directions through the casing by utilizing auxiliary igniters. This further allows for improved control of the burning of propellant throughout the casing over time.

[0029] In some embodiments, the casing comprises a base plate, and said auxiliary igniter comprises a container housing explosive that is arranged at at least an axial distance of half the diameter of the casing away from the base plate.

[0030] This has the advantage of allowing for an increased design freedom of the casing by moving the igniter(s) away from the base plate of the casing.

[0031] The present disclosure further relates to a method for igniting propellant in a cartridge. The method comprises

[0032] - providing a cartridge comprising a projectile and a casing comprising a propellant, a propellant ignition system, wherein the propellant is arranged to, upon ignition, generate gas and heat, and apply force to the projectile, wherein the propellant ignition system comprises a rapid deflagration cord, RDC, and wherein the RDC extends through the propellant and is arranged to, upon being ignited, ignite at least part of the propellant;

[0033] - providing external stimulation of the propellant ignition system, wherein said external stimulation is arranged to activate the propellant ignition system; and

[0034] - igniting the propellant, wherein igniting the propellant comprises igniting and deflagrating the RDC based on the external stimulation, thereby ejecting particles and / or heated gas from the deflagrating RDC and igniting the propellant at the RDC.

[0035] This has the advantage of allowing for reliable propellant ignition with an improved control over which parts of the propellant is ignited over time.

[0036] The present disclosure further relates to a method for producing a cartridge with a propellant ignition system comprising a rapid deflagration cord, RDC, the method comprises

[0037] - providing a casing;

[0038] - adding the propellant ignition system in the casing, wherein the propellant ignition system comprises at least one RDC;

[0039] - adding propellant into the casing; and

[0040] - placing and securing a projectile to the casing.

[0041] This has the advantage of allowing for increased flexibility in designing and positioning the propellant ignition system, thereby improving ignition performance and / or reducing weight.

[0042] BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figs, la-b schematically depict cartridges with and without a rapid deflagration cord.

[0044] Figs. 2a-c schematically depict cartridges comprising a rapid deflagration cord.

[0045] Fig. 3 shows a method for igniting propellant utilizing a rapid deflagration cord.

[0046] Figs. 4a-b schematically depict cartridges comprising auxiliary branching rapid deflagration cords.

[0047] Figs. 5a-c show activation of a propellant ignition system comprising rapid deflagration cords.

[0048] Fig. 6 shows a method for producing cartridges comprising a rapid deflagration cord.

[0049] DETAILED DESCRIPTION Throughout the figures, the same reference numerals refer to the same parts, concepts, and / or structures. Consequently, what will be said regarding a reference numeral in one figure applies equally well to the same reference numeral in other figures unless explicitly stated otherwise.

[0050] Terms and expressions

[0051] The term cartridge relates to a device comprising the components needed to fire a projectile from a weapon. Typically, a cartridge comprises a casing with a projectile, a propellant and an igniter, wherein, upon the igniter igniting the propellant, the projectile is separated and / or launched from the casing. Typically, a cartridge is designed to be inside a weapon system upon propellant ignition.

[0052] The term projectile relates to an object arranged to be launched from the cartridge, such as a bullet or a grenade.

[0053] The term base plate relates to the bottom of the casing of the cartridge. Typically, the base plate is arranged at the opposite side of the projectile in the cartridge. Depending on cartridge design the base plate may, upon igniting the propellant, remain intact, or be ruptured and / or ejected backwards, such as for recoilless rifles.

[0054] The term propellant ignition system relates to the parts of the cartridge involved in igniting the propellant upon an external stimulation. For example, the propellant ignition system may comprise an igniter arranged to ignite the propellant, and an initiator arranged to, upon external stimulation, ignite the igniter.

[0055] The term initiator relates to a device arranged to, upon activation, ignite an igniter. For example, a detonator or a blasting cap. Typically, the initiator is activated by mechanical force, heat, or electricity. Typically, the initiator ignites the igniter by providing heat to the igniter. In some examples, the initiator and igniter are comprised in the same device. In some examples, the same component serves the purpose of both initiator and igniter.

[0056] The term activation point relates to a defined location on or adjacent to the initiator (130) that is configured to receive the external stimulation and transmit it into the initiator. The activation point provides a physical and / or electrical interface, such as the surface struck by a firing mechanism, a terminal for an electrical signal, or a thermally exposed contact, through which the initiator is activated. In the figures, reference numeral 131 indicates this interface so that the place where the propellant ignition sequence originates is unambiguous.

[0057] The term external stimulation relates to a stimulus applied to the propellant ignition system to activate it, for example a mechanical impact, such as from a firing mechanism, an electrical current or signal, or a heat input, such as from a heated element. In some implementations, the external stimulation may also be provided by the deflagration of a rapid deflagration cord arranged outside the casing and coupled to the ignition system. The expression covers the form, source, and pathway by which the stimulus is delivered, without limiting the specific mechanism used to apply it. In the figures, reference numeral 132 designates such stimulation.

[0058] The term igniter relates to a device arranged to ignite propellant in firearms ammunition, fixed ammunition for artillery, or other explosive devices. Igniters typically comprise an explosive such as lead styphnate, lead azide, or tetrazene. Traditionally, the igniter is typically a container housing explosive arranged inside the cartridge at the base plate of the casing and is arranged to ignite the propellant from the base plate side of the propellant, such as a container housing boron and potassium nitrate.

[0059] The term rapid deflagration cord, RDC, relates to an explosive cord with a combustion configured to propagate through the explosive at a rate slower than the speed of mechanical waves through the explosive. Deflagration is a type of explosion that is, typically, driven by the transfer of heat. The RDC may be utilized as an igniter and / or an initiator. In some examples, an RDC may serve as both the initiator and the igniter, such as the propellant ignition system being initiated by directly igniting said RDC.

[0060] The term container housing explosive relates to, in the context of igniters, containers with explosive arranged to ignite propellant upon exploding. Typically, the container housing explosive comprises an outer structure and an explosive, wherein the outer structure fully or partially encloses the explosive. Herein, the term container housing explosive does not include rapid deflagration cords as the outer structure of an RDC is seen as an outer layer of a cord which does not resemble a traditional box-style container. In some examples, a portion of the casing of the cartridge at least partially makes up the container housing the explosive. In some examples, the container housing explosive is arranged within the casing of the cartridge.

[0061] The expression "axial distance ... from the base plate" relates to the linear separation measured parallel to the longitudinal axis of the casing between the inner face of the base plate and the closest point of the referenced feature. For example, linear separation measured parallel to the longitudinal axis between the surface bounding the propellant chamber and an auxiliary igniter or container housing explosive. This distance excludes any radial or circumferential components and is taken in the pre-ignition, unpressurised state of the cartridge. For casings with a concave or stepped base plate, the reference is typically the plane of the innermost surface that interfaces with the propellant; for tapered or shouldered casings, the measurement follows the central axis of symmetry. When expressed relative to the casing diameter, such as "at least half the internal diameter", the ratio is calculated using the internal bore diameter at the region where the feature is located, thereby ensuring an unambiguous, purely axial separation from the base plate.

[0062] The term auxiliary igniter relates to an igniter arranged to ignite propellant, and is also arranged to be ignited by the ignition of another igniter. For example, the auxiliary igniter may be an explosive coating at the rapid deflagration cord, a container housing explosives arranged to be ignited by the rapid deflagration cord, or another adjacent rapid deflagration cord arranged to be ignited by the rapid deflagration cord. Herein, the term "container housing explosives" does not include RDC unless expressly stated. The term auxiliary igniter also relates to an explosive arranged to ignite propellant that is ignited by another auxiliary igniter. Typically, the use of an auxiliary igniter serves to initially ignite more of the propellant, or to tailor the propellant burnt over time. The term auxiliary initiator relates to an initiator being arranged to ignite a corresponding auxiliary igniter, and being arranged to be activated by the ignition of an igniter.

[0063] The term high temperature particles relates to particles ejected from an igniter, such as an ignited rapid deflagration cord or an ignited container housing explosive. Typically, the high temperature particles are arranged to ignite propellant and / or an auxiliary igniter.

[0064] The expression "directly ignite propellant" relates to being the cause of an initial ignition, in contrast to subsequent ignition of propellant by adjacent propellant burning.

[0065] It is to be understood that in figures depicting cartridges, such as figs, la-b, 2a-c, and 4a-b, the example casings are filled with propellant, however, for illustrative purposes said propellant is not depicted as blocking the view of other features of the example cartridges.

[0066] Figs, la-b illustrate example cartridges 100 with different propellant ignition systems 101. Fig. la represents an example prior art solution utilizing an igniter comprising a container 170 with explosive to ignite propellant 120 arranged at the base plate 111 of the casing 110. Fig. lb schematically shows an example cartridges 100 utilizing a rapid deflagration cord, RDC, 140 as the igniter to ignite propellant 120.

[0067] Fig. la schematically shows an example state of the art cartridge comprising:

[0068] - a casing 110 arranged to house the propellant, the propellant ignition system 101 and part of a projectile 180, comprising a base plate 111,

[0069] - the propellant 120 arranged to, upon ignition, generate gas and heat, thereby applying force to the projectile 180, wherein the propellant 120 is held in position by a propellant support 160,

[0070] - the propellant ignition system 101 comprising an initiator 130 and an igniter comprising a container 170 housing explosive, wherein the initiator 130 is arranged to, upon external stimulation at an activation point 131, ignite the igniter, and wherein the igniter is arranged to, upon ignition, explode and inject high temperature particles and / or gas into the propellant 120, thereby igniting at least part of the propellant 120, and

[0071] - the projectile 180 arranged to be launched from the cartridge 100 upon ignition of the propellant 120.

[0072] Typically, container 170 housing explosive is a plastic container 170 housing explosives arranged at the base plate of the cartridge 100. A drawback with this type of igniter is that it takes up a large volume and is prone to break in an irreproducible fashion. Furthermore, design freedom of the casing 110 and base plate 111 of the cartridge 100 may be limited when in close proximity to the container 170 arranged to explode.

[0073] Typically, a cartridge 100 comprises an initiator 130 arranged to ignite an igniter 140, however, the technical effect provided by the initiator may instead be provided by the external stimulation, such as a small explosion to directly ignite an igniter of the cartridge. Therefore, the initiator is not a required component in at least some embodiments of the invention. Initiators are despite this included in the example figures, in part, to highlight where in the cartridge the activation is initiated.

[0074] In the examples shown in figs, la-b the projectile 180 comprises fins 181 arranged to fold out and stabilize the projectile 180 after exiting the casing 110, such as upon leaving the barrel of a weapon system. It is to be understood that the invention primarily relates to the ignition of propellant and that this versatile ignition solution is compatible with many different types of cartridge 100 and projectile 180 combinations.

[0075] Fig. lb schematically shows an example cartridge utilizing a rapid deflagration cord, the cartridge 100 comprising:

[0076] - a casing 110 arranged to house the propellant, the propellant ignition system and at least part of a projectile 180, and comprising a base plate 111,

[0077] - the propellant 120 arranged to, upon ignition, generate gas and heat, thereby applying force to the projectile, wherein the propellant 120 is held in position by a propellant support 160,

[0078] - the propellant ignition system 101 comprising an initiator 130 and the rapid deflagration cord 140, RDC, wherein the initiator 130 is arranged to, upon external stimulation at an activation point 131, ignite the RDC 140, and wherein the RDC 140 extends through the propellant 120 and is arranged to, upon ignition, undergo deflagration and inject high temperature particles and / or gas into the propellant 120, thereby burning at least part of the propellant 120 around the RDC 140, and - the projectile 180 arranged to be launched from the cartridge 100 upon burning of the propellant

[0079] 120.

[0080] Utilizing a propellant ignition system 101 comprising an RDC 140 instead of a traditional container 170 housing explosive may allow the volume inside the cartridge 100 to be designed more freely. The use of an RDC 140 pathing through the propellant may further allow a larger portion of the propellant to be ignited at an initial stage compared to utilizing a container 170 with explosive that is located on one side of the propellant 120, and / or may allow improved control of the burn rate of the propellant 120 over time. That is to say, the distance between propellant and igniter(s) may better be controlled when designing a cartridge 100 with a propellant ignition system 101 comprising an RDC 140 as an igniter.

[0081] One difference between the RDC 140 compared to an elongated container housing explosives is that the RDC 140, typically, propagates faster and the particles ejected from the RDC 140 are spread more predictably compared to the fragments of such exploding containers. Furthermore, the RDC 140 would typically be more easily pathed through desired regions of the casing compared to an elongated container housing explosives.

[0082] Typically, the shape of the casing 110 relates to a cylinder, and the cross-section of the casing 110 is circular. In some examples, the casing 110 cross-section is at least 20 mm in diameter. In some of these examples, the casing 110 cross-section is at least 30 mm, at least 40 mm, at least 60 mm, at least 80 mm, or at least 100 mm. Utilizing RDC 140 for igniting propellant is expected to provide an increased advantage as cartridges increase in size, providing a significant advantage for large calibre ammunition such as fixed ammunition for artillery and ammunition for recoilless rifles.

[0083] In some examples, the projectile 180 has a cross-section of at least 20 mm in diameter. In some of these examples, the projectile 180 cross-section is at least 30 mm, at least 40 mm, at least 60 mm, at least 80 mm, or at least 100 mm. Typically, the diameter of the projectile 180 corresponds to the bore diameter of the weapon system using the cartridge 100.

[0084] In some examples, the casing 110 comprises a substantially cylindrical part that is sealed at one end by the base plate 111, and, prior to propellant ignition, sealed by the projectile 180 at the other end. In some of these examples, the base plate 111 is arranged to break open and / or be ejected backwards upon ignition of the propellant 120. Typically, recoilless weapon systems are based on gas from burning propellant being ejected in a direction opposite to the direction of movement of the projectile. For recoilless rifles this is typically achieved by mounting the cartridge 100 between a forward facing opening and a backwards facing opening, such as in a tube, and wherein gas from igniting propellant 120 exits the backwards facing opening, either by moving through or past the base plate 111, and the projectile 180 exits via the forward facing opening. In some examples, the casing is arranged to become perforated upon propellant burning, and the generated gas is guided through the perforations, and if in a weapon system, gas is guided to exit via the backwards facing opening.

[0085] In some examples, the propellant 120 comprises gunpowder. In some examples, the propellant 120 is packaged in a plurality of propellant charges (not shown), and the propellant support 160 is arranged to hold said propellant charges in place inside the casing 110. In some examples, the RDC 140 is secured to the propellant support 160.

[0086] In some examples, the initiator 130 is arranged to be activated by external stimulation comprising

[0087] - impact at the activation point 131 by mechanical impact, such as from a firing pin;

[0088] - electrical current, such as from an electrical wire; and / or

[0089] - heat, such as from a hot wire.

[0090] In some examples, the initiator 130 is arranged at the casing 110. In some of these examples, the initiator 130 is integrated into the casing 110. In some examples, the initiator 130 is arranged at an end of the RDC 140.

[0091] In some examples, the RDC 140 comprises explosive material comprising at least one of cyclotrimethylene-trinitramine, hexanitrostilbene, triaminotrinitrobenzene, hexanitro-hexaazaisowurtzitane, 1,3,3-trinitroazetidine, aluminium, polyurethane, nitrocellulose, ZrBijOa, ammonium perchlorate and pentaerythritol-tetranitrate. In some examples, the explosive material comprises zirconium, calcium stearate, graphite, and polyisobutylene.

[0092] In some examples, the RDC 140 comprises a metal sheath (not shown). In some of these examples, the metal sheath comprises lead, tin, aluminium, and / or silver. A metal sheath may be arranged around the RDC 140 to increase the propagation speed of the deflagration along the RDC 140. In some of these examples, the metal sheath has a thickness in the range of 200pm to 5 mm. A metal sheath may provide a level of mechanical protection, thereby allowing an increased degree of freedom in pathing the RDC 140 through the casing 110.

[0093] In some examples, the initiator 130 comprises an electro-explosive device, an electro-pyrotechnic initiator, a percussion primer, a military grade percussion primer, a blasting cap, and / or another length of RDC.

[0094] It is to be understood that in some weapon systems the external stimulation to activate the propellant ignition system of a cartridge is the deflagration of a length of RDC outside the cartridge. In some examples, the RDC of the propellant ignition system is pathed through the propellant and further extends outside the casing of the cartridge, whereby igniting a part of said RDC outside the casing is arranged to cause the propellant to be ignited.

[0095] In some examples, the RDC 140 extends vertically along substantially the full length of the region in the casing 110 holding the propellant 120. In some examples, the RDC 140 extends vertically along at least 40% of the full length of the region of the casing 110 holding the propellant 120. In some of these examples, the RDC 140 extends vertically along at least 60%, at least 80%, or at least 90% of the full length of the region of the casing 110 holding the propellant 120.

[0096] It is to be understood that the expression "the full length of the region of the casing 110 holding the propellant 120" relates to the volume inside the casing 110, and more specifically said region includes the parts of said volume containing significant amounts of propellant 120. For example, in fig. lb, if assuming that the volume between base plate 111 and projectile 180 is filled with propellant 120, then the example RDC 140 extends vertically along at least 80% of the full length of the region of the casing 110 holding the propellant 120.

[0097] In some examples, the RDC 140 diameter is in the range of 0.2 mm to 20 mm. In some of these examples, the RDC 140 diameter is in the range of 0.4 mm to 10 mm, in the range of 0.7 mm to 5 mm, or in the range of 1 mm to 3 mm.

[0098] In some examples, cartridge 100 comprises a total length of RDC(s) 140 that is at least 20 mm. In some of these examples, said total length of RDC(s) 140 is at least 30 mm, at least 40 mm, at least 50 mm, at least 70 mm, or at least 100 mm.

[0099] In some examples, cartridge 100 comprises a total length of RDC(s) 140 that is greater than the diameter of the casing 110. In some of these examples, said total length is greater than twice the diameter of the casing 110, or greater than three times the diameter of the casing 110.

[0100] In some examples, the RDC 140 is arranged to, upon ignition, propagate the deflagration along the RDC 140 at a propagation speed of 50 to 800 m / s. In some examples, the propagation along the RDC 140 is at least 100 m / s, at least 200 m / s, or at least 400 m / s. Typically, the cartridge 100 is configured such that the RDC 140 has fully undergone deflagration before the pressure in the cartridge 100 has reached a significant fraction of the maximum pressure. Propagation speed being measured along the cord within the casing at ambient temperature and pressure prior to substantial chamber pressurization.

[0101] In some examples, the RDC 140 is pathed at least partially through and / or against the propellant support 160. In some examples, at least a portion of the RDC 140 is arranged at the propellant support 160. In some of these examples, the RDC 140 is mounted to or attached to the propellant support 160. In some examples, the RDC 140 is arranged to function as a propellant support 160, whereby at least some propellant 120 and / or propellant charges are held in place by the RDC 140. In some examples, the propellant 120, or a portion thereof, is kept in place inside the cartridge 100 by one or more RDCs 140. Utilizing the RDC 140 as a structural support for propellant 120 may allow the weight and / or size of the cartridge 100 to be reduced, alternatively an increased amount of propellant 120 may arranged inside the casing 110. In some examples, the RDC 140 is the propellant support 160, or at least provides a significant contribution to holding the propellant 120 in place. Utilizing the RDC 140 for this secondary support purpose synergizes well with the ignition of the propellant as the RDC 140 preferably extends close to propellant charges both to hold them in place and to be in close proximity to them for ignition.

[0102] In some example, the cartridge 100 does not comprise a propellant support 160. In some example, the cartridge 100 does not comprise a propellant support 160 except for any RDC 140 functioning as a propellant support.

[0103] In some examples, the RDC 140 is at least partially of a flat and wide shape, such as a plate or strip, so as to allow ignition of propellant 120 in a different surrounding region compared to the ignition pattern of a cylindrical RDC 140. In some examples, the RDC 140 comprises at least one plate shaped part, wherein each plate shaped part is arranged to ignite the propellant 120. In some of these examples, one or more of said plate shaped parts are arranged against the side of a propellant charge.

[0104] In some examples, the RDC 140 is arranged to, during ignition, propagate an explosion at at least 50 m / s along the RDC 140. In some of these examples, said ignition is arranged to propagate the explosion at at least 70 m / s, at at least 90 m / s, or at at least 120 m / s. In some examples, the RDC 140 is arranged to, during ignition, propagate at at least twice the speed of the burn rate of the propellant 120. In some of these examples, the RDC 140 is arranged to propagate at at least ten times the speed of the burn rate of the propellant 120, at least one hundred times the speed of the burn rate of the propellant 120, or at least one thousand times the speed of the burn rate of the propellant 120.

[0105] It is to be understood that for typical propellant in ammunition, the burn rate is significantly below supersonic speeds. For example, propellants of the popular smokeless powder type will typically have a burn rate of less than 1 m / s even in the high pressure environment during propellant ignition, with some propellants having a burn rate of approximately 0.1 m / s. How propellant 120 burns in a casing 110 is determined by where the propellant 120 is initially ignited. Therefore, predictably controlling which portion of the propellant 120 becomes directly ignited by the propellant ignition system 101 allows for a predictable gas generation over time in the cartridge 100. In some examples, the propellant ignition system 101 comprises a plurality of RDCs 140, each arranged to be ignited, directly and / or indirectly, by one initiator 130. In some of these examples, said plurality of RDCs 140 are each ignited by at least one initiator 130.

[0106] In some examples, the propellant ignition system 101 comprises at least one RDC 140 that splits into at least two ends. In some examples, at least one RDC 140 forms a closed loop.

[0107] In some examples, the propellant ignition system 101 comprises one or more auxiliary igniter, wherein each auxiliary igniter is ignited directly or indirectly by an igniter, such as being ignited by the RDC 140. It is to be understood that auxiliary igniters are igniters that are not ignited by the initial activation of the initiator 130, but instead are ignited subsequently as a consequence of the ignition of other igniters.

[0108] In some examples, the propellant 120 comprises at least two adjacent propellant charges, wherein gaps exist between said propellant charges, and wherein one or more igniter of the propellant ignition system is arranged in said gaps. In some of these examples, one or more RDCs 140 are arranged in said gaps.

[0109] In some examples, the propellant ignition system 101 comprises the RDC 140 and at least one additional igniter, wherein said additional igniter is arranged to, upon ignition, explode or undergo deflagration and inject high temperature particles into the propellant 120, thereby igniting at least part of the propellant 120. In some of these examples, the RDC 140 is arranged to ignite the additional igniter, wherein said igniter is an auxiliary igniter. In some of these examples, the auxiliary igniter comprises at least one container 170 housing explosive, an explosive coating at the RDC 140, and / or a length of RDC, such as containers 170 housing explosive seen in fig. 2b and branching RDCs 141 seen in figs. 4a-b.

[0110] It is to be understood that the use of the RDC 140 or other igniters to ignite another igniter may further allow improved design freedom, especially in the area inside the cartridge 100 in proximity to the base plate 111 and in distributing propellant 120 inside the casing 110. This freedom of design may be of particular importance for cartridges 100 designed to break open and / or eject the base plate 111 upon burning propellant 120.

[0111] In some of these examples, the propellant ignition system 101 comprises the RDC 140 that extends through the propellant 120 such that, upon activation, the RDC 140 at least partially directly ignites the propellant 120 at multiple different sides and / or regions of the propellant 120. Traditional propellant ignition systems 101 utilizing containers comprising explosive arranged at the base plate 111 would typically predominantly directly ignite propellant 120 in the adjacent region. In some examples, the propellant ignition system 101 comprises the RDC 140 and one or more container 170 housing explosive arranged to, upon ignition, explode and inject high temperature particles into the propellant 120, thereby igniting at least part of the propellant 120. In some of these examples, the one or more container 170 housing explosive is arranged at the RDC 140, and the RDC 140 is arranged to ignite the one or more container 170 housing explosive, whereby said containers 170 housing explosive function as auxiliary igniters.

[0112] In some examples, the propellant ignition system 101 comprises the RDC 140 and an explosive coating (not shown) arranged at at least part of the length of the RDC 140, wherein the explosive coating is arranged to, upon ignition, explode and inject high temperature particles into the propellant 120, thereby igniting at least part of the propellant 120. In some of these examples, the RDC 140 is arranged to ignite the explosive coating. In some of these examples, at least 50%, or at least 80%, of the surface of the RDC 140 is covered with said explosive coating. In some of these examples, the explosive coating is arranged on the RDC 140.

[0113] It is to be understood that the container 170 housing explosive or the explosive coating may be arranged at or in close proximity to the RDC 140 in various configurations, such that the RDC 140 may ignite the container 170 housing explosive or the explosive coating, thereby improving propellant ignition compared to a propellant ignition system 101 comprising only the RDC 140 as an igniter. In some examples, at least some explosive coating is arranged on the propellant 120.

[0114] In some examples, the cartridge 100 comprises a container 170 housing explosive, wherein said container 170 is arranged at least a predetermined axial distance away from the base plate 111. In some examples, the predetermined axial distance away from the base plate 111 is 10 mm, or 20 mm. In some examples, the predetermined distance is half the diameter of the casing 110, or the diameter of the casing 110.

[0115] In some examples, the propellant ignition system 101 comprises at least one igniter and / or auxiliary igniter comprising, boron and potassium nitrate, BPN.

[0116] Figs. 2a-c schematically depict three example cartridges that all comprise a rapid deflagration cord to ignite propellant. Fig. 2a shows a side view of part of an example cartridge 100 comprising a rapid deflagration cord 140, RDC, pathed through the propellant 120. Fig. 2b shows a side view of an example cartridge 100 comprising an RDC 140 and containers 170 housing explosive being arranged at the RDC 140, wherein said containers 170 housing explosive function as auxiliary igniters. Fig. 2c shows a top-down view of an example cartridge 100 comprising an RDC 140 pathed through the propellant

[0117] 120. It is to be understood that the example cartridges schematically depicted in figs. 2a-c and figs. 4a-b serve to illustrate the pathing flexibility of utilizing RDCs and options of combining RDCs with auxiliary igniters. The invention is not limited to the depicted examples. The propellant ignition systems of the depicted examples may not necessarily be to scale.

[0118] Fig. 2a shows the bottom part of the example cartridge 100 comprising a casing 110 filled with propellant 120 and a propellant ignition system comprising an RDC 140 running through the propellant 120 and a connected initiator 130. In this example, the RDC 140 is arranged to be within a predetermined distance of all the propellant 120 in the cartridge 100, whereby the propellant 120 throughout the casing 110 is expected to ignite and burn in a predictable manner after ignition of the RDC 140.

[0119] It is to be understood that the arrangement of the RDC 140 and the propellant 120 in the cartridge 100 is typically selected based on a desired pressure over time upon ignition of the RDC 140. Therefore, the complete ignition of propellant within a predetermined period of time may not be the primary requirement for all cartridge designs. Fig. 2a aims to illustrate the increased design options when utilizing an RDC 140 compared to utilizing one container housing explosive that is arranged at the base plate 111 of the cartridge 100, such as shown in fig. la.

[0120] In some examples, the RDC 140 is known to ignite surrounding propellant 120 within an ignition distance from the RDC 140, and the RDC 140 is pathed through the propellant 120 in the casing 110 such that at least 40% of said propellant 120 is within said ignition distance to a part of the RDC 140. In some of these examples, the RDC 140 is pathed such that at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of said propellant 120 is within said ignition distance.

[0121] In some examples, the igniters of the propellant ignition system are known to ignite surrounding propellant 120 within an ignition distance, and the one or more igniter is arranged at the propellant 120 in the casing 110 such that at least 40% of said propellant 120 is within the corresponding ignition distance of any of said igniters. In some of these examples, said igniter is arranged such that at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of said propellant 120 is within the corresponding ignition distance of igniter. In some of these examples, said igniter comprises at least one container 170 housing explosive, an explosive coating at the RDC 140, and / or a length of RDC.

[0122] Fig. 2b shows the bottom part of the example cartridge 100 comprising a casing 110 filled with propellant 120 and a propellant ignition system comprising the initiator 130, the RDC 140, and two cylindrical containers 170 housing explosive are arranged around the RDC 140. The cylindrical containers 170 are auxiliary igniters arranged to, upon ignition of the RDC 140, be ignited and ignite the propellant 120 in the casing 110.

[0123] In some examples, one or more container 170 housing explosive is arranged at the RDC 140. In some of these examples, said containers 170 housing explosive are arranged at least a predetermined axial distance from the base plate 111 of the casing 110. In some of these examples, said predetermined distance is a quarter of the casing diameter, half the casing diameter, or the casing diameter.

[0124] In some examples, two or more containers 170 housing explosive are arranged at the RDC 140. In some of these examples, three or more containers 170 housing explosive are arranged at the RDC 140.

[0125] In some examples, the RDC 140 is coated or partially coated with an explosive (not shown). In some examples, at least one auxiliary igniter comprises a length of RDC coated or partially coated with an explosive (not shown). In some examples, the container 170 housing explosive is coated or partially coated with an explosive. In some examples, at least part of the propellant is coated or partially coated with an explosive.

[0126] It is to be understood that the propellant ignition system 101 comprising the RDC 140 inside the casing 110 may utilize a combination of one or more igniter arranged to be ignited by the initiator, and one or more auxiliary igniter, such as a container 170 housing explosive, arranged to be ignited by the RDC 140. In some examples, the propellant ignition system 101 comprises an auxiliary initiator arranged to be activated by the RDC 140 and thereby ignite at least one of said container 170 housing explosive.

[0127] Fig. 2c shows a top-down view of an example cartridge 100 comprising an RDC 140 pathed through the propellant 120 with the viewer looking towards the base plate 111 through the casing 110. The RDC 140 of the example cartridge 100 is in the shape of a spiral that is attached at the initiator 130 close to the base plate 111 and extends in a spiral upwards towards the viewer. Note that fig. 2c represents a top-down view wherein, for illustrative purposes, the propellant 120 is transparent, so the RDC 140 that spirals upwards through the propellant 120 is visible.

[0128] Fig. 3 shows a method for igniting propellant in a cartridge. The method 300 comprises

[0129] - providing 310 a cartridge comprising a projectile and a casing comprising a propellant, a propellant ignition system, wherein the propellant is arranged to, upon ignition, generate gas and heat, and apply force to the projectile, wherein the propellant ignition system comprising a rapid deflagration cord, RDC, and wherein the RDC extends through the propellant and is arranged to, upon being ignited, ignite at least part of the propellant,

[0130] - providing 320 external stimulation of the propellant ignition system, wherein said external stimulation is arranged to activate the propellant ignition system, and - igniting 330 the propellant, wherein igniting 330 the propellant comprises igniting and deflagrating

[0131] 332 the RDC based on the external stimulation, thereby ejecting particles and / or heated gas from the deflagrating RDC and igniting 334 the propellant at the RDC.

[0132] In some examples, the provided 310 cartridge comprises the propellant ignition system comprising an initiator arranged to ignite the RDC, and wherein igniting 330 the propellant comprises the initiator being activated 331 by the external stimulation, and igniting the RDC.

[0133] In some examples, igniting 330 propellant comprises igniting 331 one or more auxiliary igniters by deflagrating the RDC, wherein said auxiliary igniters are arranged to, upon ignition, explode or undergo deflagration and burn propellant. In some of these examples, said one or more auxiliary igniters comprise at least one container housing explosive, an explosive coating at the RDC, a branching RDC and / or a length of RDC.

[0134] In some examples, igniting 330 propellant comprises launching 335 the projectile from the casing by forces from gas and heat generated by burning propellant.

[0135] Figs. 4a-b shows example cartridges comprising a propellant ignition system with branching RDCs. Fig. 4a shows an example cartridge 100 comprising a casing 110 filled with propellant 120 and a propellant ignition system comprising an RDC 140 running through the propellant 120, an initiator 130 arranged at one end of the RDC 140 and the casing 110, and four branching RDCs 141 arranged at the propellant 120. The RDC 140 and branching RDCs 141 are arranged such that, upon the initiator 130 igniting the RDC 140, the deflagration of the RDC 140 ignites the branching RDCs 141.

[0136] It is to be understood that utilizing the branching RDCs 141 may allow a large fraction of the propellant to be directly ignited by the propellant ignition system while avoiding an overly serpentine path of the RDC 140 ignited by the initiator 130. The term branching relates to the region being ignited branching off, and does not require a physical branching of one RDC into two directions. Creating an RDC that branch off in two directions may be technically challenging, therefore igniting a separate adjacent RDC may be a favourable option.

[0137] In some examples, the propellant ignition system comprises one or more branching RDC 141 arranged to be ignited by an RDC 140, said branching RDCs 141 being auxiliary igniters. In some examples, the propellant ignition system comprises at least two, at least four, or at least six branching RDCs 141 arranged to be ignited by the RDC 140. In some examples, the one or more branching RDC 141 is kept in close proximity to the RDC 140 that is arranged to be ignited by the initiator 130 utilizing at least one RDC holding part and / or adhesive (not shown).

[0138] In some examples, the propellant 120 comprises at least two adjacent propellant charges, wherein gaps exist between said propellant charges, and wherein one or more branching RDC 141 is arranged in said gaps.

[0139] In some examples, the propellant ignition system comprises one or more branching RDC 141 arranged to extend away from the RDC 140 arranged to be ignited by the initiator 130. Typically, the branching RDCs 141 extend away from the main RDC 140 and do not run parallel to the main RDC 140 for their full length.

[0140] Fig. 4b shows an example cartridge 100 comprising a casing 110 filled with propellant 120 and a propellant ignition system comprising an RDC 140 running through the propellant 120, an initiator 130 arranged at one end of the RDC 140 and the casing 110, and four branching RDCs 141 each with an auxiliary initiator 133. The RDC 140 and branching RDCs 141 are arranged such that, upon the initiator 130 igniting the RDC 140, the deflagration of the RDC 140 activates the auxiliary initiator 133 which ignites the branching RDCs 141.

[0141] It is to be understood that the auxiliary initiator 133 serves to increase the probability of the branching RDC 141 being ignited as a consequence of the RDC 140 ignited by the initiator 130 exploding. In some embodiments with auxiliary initiator(s) 133, the RDC 140 ignited by the initiator 130 may be able to eject particles that directly ignite a branching RDC 141.

[0142] In some of these examples, the propellant ignition system 101 comprises an auxiliary initiator 133 at said branching RDC 141 being arranged to assist in igniting said branching RDC 141. In some embodiments an RDC 140 is arranged to directly ignite adjacent branching RDCs 141. In some embodiments the RDC 140 ignites adjacent branching RDCs 141 via an auxiliary initiator 133, such as a detonator or an explosive material functioning as an initiator for the branching RDCs 141.

[0143] In some examples, the propellant ignition system 101 comprises at least one holding part and / or adhesive (not shown) arranged to hold the RDC 140, an auxiliary igniter 141 and an auxiliary initiator 133 in a position at which igniting said RDC 140 activates the auxiliary initiator 133, thereby igniting the auxiliary igniter 141. Said auxiliary igniter held in position may be a branching RDC 141 and / or a container 170 housing explosive, such as shown in fig. 2b. Figs. 5a-c shows activation of a propellant ignition system comprising rapid deflagration cords. Figs. 5a- c illustrate a time series for the activation of an example propellant ignition system corresponding to the example cartridge in fig. 4a.

[0144] Fig. 5a illustrates an external stimulation 132 of the initiator 130 causing the initiator 130 to ignite the RDC 140. Fig. 5b illustrates the deflagration of the RDC 140. Fig. 5c illustrates the deflagration of four branching RDCs 141, and the volume 121 of burnt and / or burning propellant. It is to be understood that the time series aims to conceptually illustrate the propellant ignition system comprising an igniter and an auxiliary igniter being exploded in a casing filled with propellant 120. The time series is a simplification and may differ from the evolution of a real propellant ignition system upon activation.

[0145] Fig. 5a shows an example cartridge 100 comprising a casing 110 filled with propellant 120 and a propellant ignition system comprising an RDC 140 running through the propellant 120, the initiator 130 arranged at one end of the RDC 140 and the casing 110, and four branching RDCs 141 arranged at the propellant 120. An external stimulation 132, here in the form of a mechanical impact, activates the initiator 130 which causes it to ignite the RDC 140.

[0146] Fig. 5b shows the RDC 140 deflagrating as a consequence of the ignition at the RDC 140 by the initiator 130. The deflagration of the RDC 140 ejects heated particles and gas radially out from the deflagrating RDC 140 towards the surrounding propellant 120 and the four branching RDCs 141.

[0147] Fig. 5c shows the four branching RDCs 141 deflagrating as a consequence of being ignited by the ejected heated particles and gas from the deflagrated RDC 140. Fig. 5c further illustrates a volume 121 of burnt and / or burning propellant ignited by the deflagrated RDC 140, and a front line 122 against the propellant 120. The deflagrating four branching RDCs 141 ejects heated particles and gas into the surrounding propellant 120. Ejected heated particles and gas from the deflagrated four branching RDCs 141 will ignite the surrounding propellant 120 in a manner corresponding to the volume 121 of burnt and / or burning propellant around the deflagrated RDC 140 (not shown).

[0148] In the example time series of figs. 5a-c, the RDC 140 and the four branching RDCs 141 undergo deflagration before the projectile (not shown) of the cartridge separates from the casing 110 due to pressure from burning propellant. For example, the RDC 140 and the four branching RDCs 141 undergo deflagration before half of the propellant 120 is ignited. In some examples, the cartridge 100 is arranged to have all RDCs 140,141 complete deflagration before 60% or 80% of the propellant is burnt.

[0149] Fig. 6 shows a method for producing cartridges comprising a rapid deflagration cord. The method 400 comprises

[0150] - providing 410 a casing; - adding 420 the propellant ignition system in the casing, wherein the propellant ignition system comprises at least one RDC;

[0151] - adding 430 propellant into the casing; and

[0152] - placing 440 and securing a projectile to the casing.

[0153] In some examples, the propellant ignition system and propellant is added together into the casing. In some of these examples, the one or more RDCs are and propellant are integrated before adding to the casing. For example, the propellant may be arranged in satchels held in place by one or more RDCs prior to adding the propellant ignition system and propellant into the casing, alternatively the propellant ignition system and propellant may be one integrated unit.

[0154] In some examples, at least one RDC is inserted into the casing after adding 430 propellant into the casing. In some examples, at least one initiator is inserted into the casing after adding 430 propellant into the casing.

[0155] In some examples, upon adding 430 propellant into the casing and adding 420 the propellant ignition system in the casing, the at least one RDC extends through the propellant.

[0156] In some examples, providing 410 the casing comprises mounting the base plate into the casing.

[0157] In some examples, adding 420 the propellant ignition system comprises positioning said RDC at an initiator, wherein the initiator is arranged to ignite said RDC.

[0158] It is to be understood that adding 420 the propellant ignition system may comprise mounting an initiator at the casing for external access, inserting the remaining propellant ignition system into the casing, and then interfacing an RDC of the propellant ignition system with the initiator inside the casing.

[0159] In some examples, adding 420 the propellant ignition system comprises positioning the initiator at the casing. In some of these examples, the initiator is integrated into the casing.

[0160] In some examples, adding 420 the propellant ignition system comprises positioning the RDC at the casing. In some of these examples, the RDC is integrated into the casing.

Claims

CLAIMS1. A cartridge (100) comprising:- a casing (110) arranged to house a propellant (120), a propellant ignition system (101) and at least part of a projectile (180),-the propellant (120) arranged to, upon ignition, generate gas and heat in the casing (110), thereby applying force to the projectile (180),- the propellant ignition system (101) comprising a rapid deflagration cord (140), RDC, wherein the RDC (140) extends through the propellant (120) and is arranged to, upon ignition, undergo deflagration and inject high temperature particles and / or gas into the propellant (120), thereby igniting at least part of the propellant (120) around the RDC (140), and- the projectile (180) arranged to be launched from the cartridge (100) upon ignition of the propellant (120).

2. The cartridge according to claim 1, wherein the propellant ignition system (101) comprises an initiator (130) being arranged to, upon activation by external stimulation (132), ignite the RDC (140).

3. The cartridge according to claim 2, wherein the initiator (130) comprises a detonator, an electro-explosive device, an electro-pyrotechnic initiator, a percussion primer, a blasting cap, or a length of RDC.

4. The cartridge according to any preceding claim, wherein the casing (110) comprises a propellant support (160) arranged to hold the propellant (120) in position inside the casing (110), wherein at least a portion of the RDC (140) is arranged at the propellant support (160) and / or at least a portion of the RDC (140) is arranged to function as the propellant support (160).

5. The cartridge according to any preceding claim, wherein the casing (110) cross-section is at least 20 mm in diameter.

6. The cartridge according to any preceding claim, wherein the RDC (140) comprises a metal sheath encasing the explosive material of the RDC (140).

7. The cartridge according to any preceding claim, wherein the RDC (140) is arranged to, upon ignition, propagate the deflagration along the RDC (140) at a propagation speed of 50 to 800 m / s, wherein propagation speed is measured along the cord within the casing at ambient temperature and pressure prior to substantial chamber pressurization.

8. The cartridge according to any preceding claim, wherein the RDC (140) comprises explosive material comprising one or more of cyclotrimethylene-trinitramine, hexanitrostilbene, triaminotrinitrobenzene, hexanitrohexaazaisowurtzitane, 1,3,3- trinitroazetidine, aluminium, polyurethane, nitrocellulose, zirconium and bismuth(lll) oxide, ammonium perchlorate, and pentaerythritol-tetranitrate; and / or explosive material comprising calcium stearate, graphite, and polyisobutylene.

9. The cartridge according to any preceding claim, wherein the casing (110) comprises a cylindrical part that is sealed at one end by a base plate (111), and initially sealed by the projectile (180) at the other end, wherein the base plate (111) is arranged to break open and / or be ejected backwards upon ignition of the propellant (120).

10. The cartridge according to any preceding claim, wherein the propellant ignition system (101) comprises the RDC (140) and an auxiliary igniter (141,170), wherein the RDC (140) is arranged to ignite the auxiliary igniter (141,170), and wherein the auxiliary igniter (141,170) is arranged to, upon ignition, explode or undergo deflagration and inject high temperature particles into the propellant (120), thereby igniting at least part of the propellant (120).

11. The cartridge according to claim 10, wherein the casing (110) comprises a base plate (111), and wherein said auxiliary igniter (141,170) comprises a container (170) housing explosive that is arranged at at least an axial distance of half the diameter of the casing (110) away from the base plate (111).

12. A method for igniting propellant in a cartridge, the method (300) comprises- providing (310) a cartridge (100) comprising a projectile (180) and a casing (110) comprising a propellant (120), a propellant ignition system (101), wherein the propellant (120) is arranged to, upon ignition, generate gas and heat, and apply force to theprojectile (180), wherein the propellant ignition system (101) comprises a rapid deflagration cord (140), RDC, and wherein the RDC (140) extends through the propellant (120) and is arranged to, upon being ignited, ignite at least part of the propellant (120);- providing (320) external stimulation (132) of the propellant ignition system (101), wherein said external stimulation (132) is arranged to activate the propellant ignition system (101); and- igniting (330) the propellant (120), wherein igniting (330) the propellant (120) comprises igniting and deflagrating (332) the RDC (140) based on the external stimulation (132), thereby ejecting particles and / or heated gas from the deflagrating RDC (140) and igniting (334) the propellant at the RDC (140).

13. The method according to claim 12, wherein the propellant ignition system (101) of the provided (310) cartridge (100) comprises an initiator (130) arranged to ignite the RDC (140), and wherein igniting (330) the propellant (120) comprises the initiator (130) being activated (331) by the external stimulation (132), and igniting the RDC (140).

14. The method according to claim 12 or 13, wherein igniting (330) propellant (120) comprises deflagrating one or more branching RDC (141), container (170) housing explosive and / or an explosive coating at the RDC (140) by deflagrating the RDC (140), wherein said branching RDC (141), container (170) housing explosive and / or explosive coating is arranged to, upon exploding or deflagrating, burn propellant (120).

15. Method for producing a cartridge (100) with a propellant ignition system (101) comprising a rapid deflagration cord (140), RDC, the method (400) comprises- providing (410) a casing (110);- adding (420) the propellant ignition system (101) in the casing (110), wherein the propellant ignition system (101) comprises at least one RDC (140);- adding (430) propellant (120) into the casing (110); and- placing (440) and securing a projectile (180) to the casing (110).

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