A shotgun cartridge

Abstract

A shotgun cartridge 1 comprising a casing 2 with, propellant 5, wadding 4 and projectile 3 housed within the casing, with the wadding being housed between the propellant and the projectile separating

Description

The present application relates to a shotgun cartridge, wadding for a shotgun cartridge and processes for manufacturing the same. 5 Background Shotgun ammunition, known as shotgun cartridges, typically comprise a projectile of lead shot. When fired, shot contacts the wall of the gun barrel causing a small amount of wear. Because lead is softer than the metals used for manufacturing gun barrels, this 10 wear remains at an acceptable level. However, in recent years there has been a move toward non-toxic projectile variants for the shooting of game and other forms of sporting shooting. Non-toxic projectiles are typically harder than lead and include steel shot. This increased hardness significantly increases the wear rate of gun barrels and is a particular problem for owners of valuable older guns, where the metal used is 15 relatively soft. Summary According to one aspect of the invention, there is disclosed a shotgun cartridge comprising: 20 a casing, propellant, wadding and a projectile; the propellant, wadding and projectile being received within the casing with the wadding disposed between the propellant and the projectile to separate the propellant from the projectile; wherein the wadding comprises a cylindrical wall forming a tube and an end wall closing one end of the tube, 25 wherein the wadding is provided with a lubricant located on an outwardly facing surface of the cylindrical wall, and wherein the lubricant is a food grade fluid or grease lubricant. The projectile may be within the cylindrical wall of the wadding. 30 The projectile may be entirely within the cylindrical wall of the wadding. The lubricant may be a food grade grease. 35 The food grade grease may be a silicone grease. The lubricant maybe provided on the outwardly facing surface in an amount between 40 pg / mm2and 200 pg / mm2; or between 50 pg / mm2 and 150 pg / mm2; or between 90 pg / mm2 and 140 pg / mm2. 5 The wadding may be formed from a fibre-based material. The projectile may comprises pellets. The projectile may comprise steel pellets. 10 According to another aspect of the invention, there is disclosed wadding for a shotgun cartridge, the wadding being configured to separate the propellant from a projectile within a casing of a shotgun cartridge, wherein the wadding comprises a cylindrical wall forming a tube and an end wall closing one end of the tube, wherein the wadding is 15 provided with lubricant located on an outwardly facing surface of the cylindrical wall, and wherein the lubricant is a food grade fluid or grease lubricant. The lubricant may be a food grade grease. 20 The food grade grease may be a silicone grease. The lubricant may be provided on the outwardly facing surface in an amount between 40 pg / mm2 and 200 pg / mm2; or between 50 pg / mm2 and 150 pg / mm2; or between 90 pg / mm2 and 140 pg / mm2. 25 The wadding maybe formed from a fibre-based material. According to another aspect of the invention, there is disclosed a process of manufacturing wadding for a shotgun cartridge, the process comprising: 30 providing wadding comprising a cylindrical wall forming a tube and an end wall closing one end of the tube, providing the wadding with a lubricant on an outwardly facing surface of the cylindrical wall, wherein the lubricant is a food grade fluid or grease lubricant. 35 Providing the wadding with a lubricant may comprise rolling the wadding across a surface provided with the lubricant. According to another aspect of the invention, there is disclosed a process of manufacturing a shotgun cartridge, the process comprising: providing wadding comprising a cylindrical wall forming a tube and an end wall 5 closing one end of the tube, providing the wadding with a lubricant on an outwardly facing surface of the cylindrical wall, wherein the lubricant is a food grade fluid or grease lubricant; and incorporating the wadding into a case of the cartridge. i o Brief Description of the Drawings Fig.i illustrates a cartridge in accordance with an example of the invention. Detailed Description In embodiments of the present invention, there is provided wadding 4 for a shotgun 15 cartridge comprising a food grade fluid or grease lubricant 18. Also, in accordance with embodiments of the invention, there is provided a shotgun cartridge 1 comprising the wadding 4. Fig. 1 illustrates the shotgun cartridge 1 in cross section according to an embodiment of 20 the invention. The cartridge 1 comprises a casing 2 which houses a projectile 3, the wadding 4 and a propellant 5. The casing 2 has a cylindrical wall 6 forming a tube that is closed at one end by a cap 7 containing a primer 8 and at the other by disc shaped lid 9 secured by an inwardly turned crimped end 10 of the cylindrical wall 6. The wadding 4 divides an interior of the casing 2 in two, separating the propellant 5 from the 25 projectile 3 - the propellant 5 is provided adjacent the cap 7, while the projectile 3 is provided the other side of the wadding 4. In use, the shotgun cartridge 1 is loaded and fired in the conventional way. The primer 8 is set into the cap 7 and is configured to ignite the propellent 5 when contacted by a firing pin to displace the wadding 4 and discharge the projectile 3 down a barrel of a shot gun. The wadding 4 seals the gasses 30 generated by ignition of the propellant 5 and ensures that energy in the gas is not wasted by leakage between the projectile 3 and the cylindrical wall 6 of the casing 2 and, thereafter, between the projectile 3 and the barrel. In the example of Fig. 1, the wadding 4 is cup-shaped wadding 4, comprising a cylindrical wall 12 forming a tube and an end wall 13 closing one end of the tube. The cylindrical wall 12 has a diameter 35 substantially equal to or slightly less than the diameter of the cylindrical wall 6 of the casing 2 so that the wadding tightly fits within the cylindrical wall 6 of the casing 2. A nitro card 20 is provided between the wadding 4 and the propellant 5. The nitro card is a thin treated disc of fire-resistant card that acts to prevent burning propellant 5 igniting the wadding 4. 5 The end wall 13 may be formed as a disc shaped plug 14 within the cylindrical wall 12, as illustrated, or, alternatively, may be formed from cut and folded ends of the cylindrical wall 12. The end wall 13 is provided adjacent the propellant 5 and separates an interior 15 of the wadding 4 from the propellant. The projectile 3 is provided within the interior 15 of the wadding 4 - that is to say, within the cylindrical wall 12 of the 10 wadding 4. When the cartridge of Fig. 1 is fired, the wadding 4 and the projectile 3 are driven down the barrel together with the projectile 3 retained within the interior 15 of the wadding 4. In this way, the projectile 3 is kept separate from the barrel’s inner surface by the cylindrical wall 12 of the wadding 4, protecting the barrel from abrasion that would otherwise be caused by the projectile 3 contacting the barrel. This reduces 15 wear to the barrel that would otherwise result from contact between the projectile 3 and the barrel. As mentioned, the wadding 4 helps to seal the gasses generated by ignition of the propellant 5. This sealing effect of the wadding 4 may be assisted by an optional skirt 16. The skirt 16 is a relatively short extension of the cylindrical wall 12 beyond the end wall 13. In this example, the skirt 16 comprises crimped ends that secure the nitro 20 card 20 up against the end wall 13 of the wadding 4. Alternatively, the nitro card 20 can also be loaded resting on top of the propellant 5 without the need for crimping. Both options can be implemented for ease of manufacturing. The illustrated projectile of the above-described example cartridge 1 comprises pellets 25 of steel 17. The pellets 17 are spherical for optimal flight characteristics. While steel pellets 17 are used in the illustrated example, other projectiles 3 maybe swapped out as appropriate and depending on the intended use of the cartridge 1. For example, the pellets 17 maybe formed from other metals. Slugs and flechettes are just two further unillustrated examples that will be familiar to the skilled person and it will be 30 appreciated that the invention is not to be limited by projectile type. The wadding 4 of the above-described example cartridge 1 may be made from any suitable material such as plastic, cork or a fibre-based material such as paper. Additionally, the fibre-based material may be biodegradable. It is to be appreciated that 35 any suitable grammage of fibre-based material may be selected for use as the wadding material. Typically, a fibre-based material with a grammage between too gsm and 400 gsm may be used. The food grade fluid or grease lubricant 18 (hereinafter ‘lubricant 18’) is located on an 5 outwardly facing surface of the cylindrical wall 12 of the wadding 4. It will be appreciated that the wadding 4 of the present invention is produced separately and can be provided as such for combination with the remaining features of the cartridge 1 in any suitable way. Details of manufacture of the cartridge 1 will be 10 omitted for being within the purview of a skilled person presented with the wadding 4 manufactured according to the example described herein. In one example, the lubricant 18 is applied to the cylindrical wall 12 of the wadding 4 by rolling the wadding across a surface provided with the lubricant 18. In this way, the 15 external surface of the cylindrical wall 12 of the wadding 4 is coated in the lubricant 18. In one example, the lubricant 18 has a flash point greater than 100 Celcius or, more preferably, 150 Celcius. The lubricant 18 is thereby prevented from burning off as a result of ignition of the propellant 5, allowing at least a portion of the lubricant to serve 20 the advantages identified herein. In one example, the lubricant 18 is a grease. A grease has the advantage of being relatively more viscous than a fluid lubricant when not subject to mechanical shear. In such examples, the wadding 4 is provided with a longer shelf-life as the grease more 25 readily persists on the surface of the wadding 4, particularly where the wadding 4 is made of a fibrous material. In one example, the lubricant 18 is a grease with a NLGI number of between 1 and 3. In one example, the NLGI number is 2. The NLGI number is a measure of consistency and, therefore, the stability of the lubricant at an ambient temperature (25 Celcius). 30 An example grease that accords with the requirements established herein is provide by Brit-Lube under their part number BL-10512. The identified grease is a chemically inert, high temperature silicone grease that is food safe. It will be appreciated that equivalent food safe greases or silicone greases may provide the advantages identified 35 herein. In some examples, the lubricant 18 may be applied to the exterior of the cylindrical wall 12 of the wadding 4 in an amount between 40 pg / mm2 and 200 pg / mm2. Preferably, the amount of lubricant 18 applied maybe between 50 pg / mm2 and 150 pg / mm2. More preferably, the amount of lubricant 18 applied maybe between 90 pg / mm2 and 140 5 pg / mm2. In such examples, the wadding 4 may be formed of a fibrous material such as paperboard and maintain the advantages set out herein. In such examples, the wadding 4 maintains the advantages set out herein irrespective of whether a grease or fluid lubricant 18 is used. 10 In one example, wadding 4 for a 0.410 shotgun cartridge is provided. The cylindrical wall 12 of the wadding 4 of the present example comprises an external surface area of about 1100mm2 and is evenly loaded with 0.15g of grease, resulting in a lubricant loading of 136±io pg / mm2. The wadding 4 of this example may be made of a fibrous material such as paperboard. 15 In another example, wadding 4 for a 10-bore shotgun cartridge is provided. The cylindrical wall 12 of the wadding 4 of the present example comprises an external surface area of about 2900mm2 and is evenly loaded with 0.25g of grease, resulting in a lubricant loading of 86±io pg / mm2. The wadding 4 of this example may be made of a 20 fibrous material such as paperboard. In the examples described herein, due to the lubricant 18 being provided on the exterior surface of the cylindrical wall 12 of the wadding 4, the lubricant 18 lubricates the exterior surface of the wadding 4 contacting the barrel when the cartridge 1 is 25 discharged in use. Providing the wadding 4 with lubricant 18 has a number of advantages. Two example advantages are: 1) Improved ballistic performance of the cartridge; and 2) reduced wear to the barrel of the gun, particularly when using steel shot or other relatively hard 30 projectiles 3. 1) Improved ballistic performance: Providing the wadding 4 with a lubricant 18 reduces the friction between the wadding 4 and the barrel of the gun through which it is discharged. As the wadding 4 travels down 35 the barrel, the wadding 4 tends to remain in contact with the internal surface of the barrel over substantially the full length of the barrel. Reducing the friction between the wadding 4 and the internal surface of the barrel significantly decreases the proportion of the propellant’s 5 energy spent overcoming this friction, allowing a larger proportion of the energy to be converted to the kinetic energy of the projectile 3. This in turn allows the projectile 3 to retain more momentum down range for a better effect on target. 5 Practically speaking, in the case of shooting game, this retention of momentum increases the chance of a clean kill at ranges beyond that usually achieved for ‘conventional’ cartridges - that is to say, cartridges having wadding without lubricant 18. The coefficient of friction between the wadding 4 and the barrel using the lubricant 18 in accordance with the examples of the invention is between 0.09 and 0.19, 10 depending on the metallurgy of the barrel. This is a significant improvement over wadding without lubricant, particularly traditional fibrous wad cups, which can have a coefficient of friction as high as 0.57. 2) Reduced wear to the gun barrel 15 Small amounts of the lubricant 18 will be deposited on the internal surface of the barrel by the wadding 4 following discharge of the cartridge. These deposits help to mitigate wear caused by the projectile 3 contacting the internal surface of the barrel by acting as a barrier between the projectile 3 and the barrel. This prevents direct contact of the projectile 3 and barrel as the projectile 3 traverses the barrel when fired, reducing the 20 abrasive wear that would otherwise result. Another wear mechanism associated with the use of conventional cartridges is the deposition of microscopic particles of projectile in the barrel between shots acting as an abrasive during subsequent shots. In particular, subsequently fired wadding adheres to 25 these microscopic deposits and drags them down the barrel. This will cause gradual wear to the barrel and choke tubes as well as making shots less effective due to reduced velocity of the projectile caused by the increased friction between the wadding and the internal surface of the barrel. This is particularly problematic where steel shot is used due to its hardness and high abrasiveness. This wear mechanism is mitigated by the use 30 of the lubricated wadding 4 described herein. The deposits of lubricant 18 that collect in the barrel when discharging the cartridge 1 act as a barrier to these abrasive particles to prevent their contact with the barrel. Furthermore, with each subsequent shot, the abrasive particles and deposits of lubricant 18 are wiped away by the transit of wadding 4 down the barrel and a fresh layer of lubricant 18 laid in its stead. Therefore, use of 35 such a cartridge 1 negates the negative effects of such build-up of abrasive particles, particularly where steel shot and other hardened projectiles are used. Furthermore, the wadding 4 described herein ensures that the cartridge can be used for the shooting of game which is to be sold to game dealers as the lubricant i8is food grade and non-toxic and can thus be present in the food chain. -9-

Claims

1. A shotgun cartridge comprising:a casing, propellant, wadding and a projectile; the propellant, wadding and projectile5 being received within the casing with the wadding disposed between the propellant and the projectile to separate the propellant from the projectile;wherein the wadding comprises a cylindrical wall forming a tube and an end wall closing one end of the tube,wherein the wadding is provided with a lubricant located on an outwardly facingio surface of the cylindrical wall, andwherein the lubricant is a food grade fluid or grease lubricant.

2. A shotgun cartridge according to claim 1, wherein the projectile is within the cylindrical wall of the wadding; and, optionally, wherein the projectile is entirely within 15 the cylindrical wall of the wadding.

3. A shotgun cartridge according to claim 1 or claim 2, wherein the lubricant is a food grade grease and, optionally, wherein the food grade grease is a silicone grease.20 4. A shotgun cartridge according to any of claims 1 to 3, wherein the lubricant isprovided on the outwardly facing surface in an amount between 40 pg / mm2 and 200 pg / mm2, or between 50 pg / mm2 and 150 pg / mm2, or between 90 pg / mm2 and 140 pg / mm2.25 5. A shotgun cartridge according to any of claims 1 to 4, wherein the wadding isformed from a fibre-based material.

6. A shotgun cartridge according to any preceding claim, wherein the projectile comprises pellets.

307. A shotgun cartridge according to claim 6, wherein the projectile comprises steel pellets.

8. Wadding for a shotgun cartridge, the wadding being configured to separate the 35 propellant from a projectile within a casing of a shotgun cartridge, wherein the wadding comprises a cylindrical wall forming a tube and an end wall closing one end of the tube,wherein and the wadding is provided with lubricant located on an outwardly facing surface of the cylindrical wall, and wherein the lubricant is a food grade fluid or grease lubricant.5 9. Wadding according to claim 8, wherein the lubricant is a food grade grease and,optionally, wherein the food grade grease is a silicone grease.

10. Wadding according to claim 8 or claim 9, wherein the lubricant is provided on the outwardly facing surface in an amount between 40 pg / mm2 and 200 pg / mm2, or 10 between 50 pg / mm2 and 150 pg / mm2, or between 90 pg / mm2 and 140 pg / mm2.

11. Wadding according to any of claims 8 to 10, wherein the wadding is formed from a fibre-based material.15 12. A process of manufacturing wadding for a shotgun cartridge, the processcomprising:providing wadding comprising a cylindrical wall forming a tube and an end wall closing one end of the tube,providing the wadding with a lubricant on an outwardly facing surface of the 20 cylindrical wall, wherein the lubricant is a food grade fluid or grease lubricant.

13. A process according to claim 12, wherein providing the wadding with a lubricant comprises rolling the wadding across a surface provided with the lubricant.25 14. A process of manufacturing a shotgun cartridge, the process comprising:providing wadding comprising a cylindrical wall forming a tube and an end wall closing one end of the tube, providing the wadding with a lubricant on an outwardly facing surface of the cylindrical wall, wherein the lubricant is a food grade fluid or grease lubricant; and30 incorporating the wadding into a case of the cartridge.

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