Patent Application
20230324153
The present invention is directed to ammunition cartridge casing modifications for improving performance.
In an ammunition cartridge for a firearm, a casing holds a projectile (e.g., a bullet). Retention force is the amount of force that would be necessary to pull the projectile from the casing. Cartridge design may impact cartridge parameters such as retention force, shelf-life, durability, and/or manufacturing processes along with ballistic performance such as reliability, accuracy, and/or muzzle energy, among other aspects.
A cartridge for a firearm comprises a projectile and a case. The case comprises a base configured to hold a primer, a body extending from a first end adjacent the base to a second end, and a two-stage neck adjacent the second end of the body and configured to retain the projectile, the two-stage neck comprising a neck length, an interior, and an exterior. The interior of the two-stage neck comprises an interference band that is adjacent the second end of the body and comprises an interference diameter extending an interference length along the two-stage neck, the interference band configured to provide an interference fit with the projectile resulting in an interference retention force. The interior of the two-stage neck also comprising a clearance band comprising a clearance diameter and extending a clearance length along the two-stage neck, the clearance diameter being greater than the interference diameter, the clearance band configured to provide an interference fit with the projectile resulting in a clearance retention force, and a transition portion located between and adjoining the interference band and the clearance band. The interference retention force is greater than the clearance retention force, both the interference band and the clearance band are at least partially coextensive with the projectile, and one or more of the interference length and the clearance length comprise about 25% or more of the two-stage neck length.
The above summary of the various representative embodiments of the invention is not intended to describe each illustrated embodiment or every implementation of the invention. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices of the invention. The Figures in the detailed description that follow more particularly exemplify these embodiments.
The invention can be completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
While the invention is amenable to various modifications and alternative forms, specifics thereof have been depicted by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Relevant to all of the figures disclosed herein, certain features of the present invention may be exaggerated for clarity and illustrative purposes only. Generally, many applicable standard cartridges have an exterior neck diameter less than 0.5000″, including diameters as low as of 0.220″ or less. Some embodiments of the present disclosure relate to modifications to the interior and/or exterior diameter of a cartridge neck, such as, for example, modifications that are in the range of approximately 0.0001″-0.0010″. As such, the modifications may be difficult to see with the naked eye and/or inside the range of conventional manufacturing tolerances. As one example,
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In certain embodiments, the interference band 58 comprises an interference diameter 64 of an interior surface 66 and extends for an interference length 68 along the two-stage neck 32. An exterior surface 70 of the interference band 58 comprises an exterior diameter 72. In some embodiments, the interference band 58 may provide an interference fit when the projectile 100 engages the interior surface 66 to be positively held in the case 22, resulting in an interference retention force. In these embodiments, the interference band 58 is at least partially coextensive with the projectile 100 and is not positioned entirely behind the projectile when the projectile is seated in the case.
The design of the interference band 58 may be tuned to a desired interference retention force that precludes or reduces the need for crimping after the projectile 100 is seated. In other words, the number of crimps and/or the degree of crimping may be reduced or eliminated for any one or more crimps along the two-stage neck 32 and/or at the terminal edge 50. For example, the interference retention force may be tuned by changing the interference length 68, the interference diameter 64, selecting a case material with different rigidity, changing the thickness of the two-stage neck 32 at the interference band 58, changing the angle of the interference band 58 to be an increasing or decreasing diameter towards the clearance band 60, changing geometry of the clearance band 60, or the like.
In some embodiments, the interference retention force may be increased by one or more crimps (not shown) pressing the interference band 58 radially inwardly into the projectile 100 and/or pressing the clearance band 60 radially inwardly into the projectile (for example, a mouth crimp). However, as discussed further below, other embodiments of the present disclosure provide a desired retention force without the need for any crimping, interfitting parts, or the like.
In some embodiments, the clearance band 60 comprises a clearance diameter 80 of an interior surface 82 and extends a clearance length 84 along the two-stage neck 32. In certain embodiments, the clearance diameter is greater than the interference diameter 64. An exterior surface 86 of the clearance band 60 comprises an exterior diameter 88. In various embodiments, the clearance band 60 may provide different fits with a projectile 100 including an interference fit with the clearance diameter 80 less than the projectile diameter and providing some retention force, a line-to-line fit with the clearance diameter 80 substantially equal to the projectile diameter and providing minimal retention force relative to the retention force provided by the interference band 58, or a clearance fit with the interior surface 82 radially spaced from the projectile 100.
The fit of the clearance band 60 with the projectile 100 results in a clearance retention force. In embodiments with a clearance fit, the clearance retention force may be 0%, or substantially zero percent, or about 0%-5%, about 5%-15%, about 15%-25%, about 25%-35%, about 35%-45%, about 45%-55%, about 55%-65%, about 65%-75%, about 75%-85%, between 85%-75%, and ranges therebetween. In any disclosed embodiments, the clearance band 60 is at least partially coextensive with the projectile when the projectile is seated in the case, in order to provide the fit and other benefits disclosed herein; therefore, the clearance band is not positioned entirely behind or in front of the projectile 100 when the projectile is seated in the case.
In certain embodiments, the two-stage neck 32 may provide an overall retention force on a projectile 100 that may be either a combination of the clearance and interference retention forces or may be equivalent to the interference retention force alone. In some embodiments, the interference retention force constitutes the entire or substantially the entire overall retention force of the two-stage neck 32 on the projectile. In some embodiments, the clearance diameter 80 is greater than or equal to the interference diameter 64 and the clearance retention force is less than the interference retention force. In certain embodiments, the clearance diameter is greater than the interference diameter by a range of about 0.0001-0.0050″, about 0.0001-0.0040″, about 0.0001-0.0030″, about 0.0001-0.0020″, about 0.0001-0.0010″, about 0.0001-0.0005″, and ranges therebetween. In embodiments, the interior surface 82 of the clearance band 60 (or the entire interior 54 of the two-stage neck 32) comprises clearance portions that have a diameter greater than the interference diameter, for example axially-extending grooves, concave dimples, or the like, resulting in the clearance band 60 providing relatively less contact with the projectile 100 than the interference band 58 or a conventional neck of the same material. In embodiments, the clearance band 60 comprises a material with lower strength and/or rigidity than a material that comprises the interference band 58.
The neck length 52 is a combination of the interference length 68 and the clearance length 84 and also may include a length of the transition 62 and/or a mouth 90 if present. In embodiments, the interference length 68 comprises about 10% of the neck length 52; in other embodiments, the interference length comprises about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, or about 75% of the neck length, and ranges that include combinations of any such interference lengths. As such, in embodiments, the clearance length 84 comprises about 90% of the neck length 52; in other embodiments, the clearance length comprises about 85%, about 80%, about 75%, about 70%, about 65%, about 60%, about 55%, about 50%, about 45%, about 40%, about 35%, about 30%, or about 25% of the neck length, and ranges that include combinations of any such clearance lengths. In another sense, embodiments of the present disclosure provide both the interference length 68 and the clearance length 84 comprising at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, and at least 40% of the neck length 52, and ranges that include combinations of any such lengths. In still another sense, embodiments of the present disclose provide one or more of the interference length 68 and the clearance length 84 comprising about 10-90%, about 15-85%, about 20-80%, about 25-75%, about 30-70%, or about 35-65% of the neck length 52. In one embodiment, a two-stage neck 32 comprises a neck length 52 of about 0.300″ and the interference length 68 is about 15% or about 0.050″ and the clearance length 84 is about 85% or about 0.250″.
It will be appreciated that the disclosed embodiments of the interference band 58 are distinct from a conventional crimp, an abutting seat, other retention enhancements, or other incidental features of a case. A conventional case crimp forms a projection in an interior neck surface toward the projectile, but the interior neck surface then continues on both sides of the crimp at a consistent diameter. Therefore a crimp necessarily has two transitions: one inward from the surface and one outward back to the surface. By contrast, embodiments of the present disclosure provide only a single transition 62 between surfaces of different diameters. Additionally, in certain embodiments, the projectile 100 does not have any complementary features or shapes relative to the transition 62 and is not penetrated by, and does not otherwise mirror, the transition 62.
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In certain embodiments, the interior diameter (e.g., interference diameter 64) of the interference band 58 is the same as or less than the diameter of the projectile 100, causing the interference fit. Interference fit, as used herein, is known term of art, sometimes also referred to as press fits and/or shrink fits, referring to a traditional method for joining cylindrical parts. Generally, in an interference fit, the inner part, such as a shaft, bearing, bushing, or in our case a projectile, is machined to be bigger (e.g., have a larger width, diameter, etc.) than the mating opening (e.g., interference diameter) of the outer part, such as a housing, or casing 22. The larger part is then forced (e.g., pressed) into the smaller part, causing both parts deform slightly and fit together. This method of joining creates extremely high friction between two parts (e.g., larger part and smaller part) that can withstand large amounts of torque without separation of the parts.
In certain embodiments, the interference diameter 64 is about 0.0010″ less than the projectile diameter, more generally about 0.0005″-0.0015″, more generally the interference diameter 64 is smaller than the projectile diameter by about 0.0020″ or less. In some embodiments, the clearance band 560 is at least partially coextensive with the ogive portion 102, thereby accommodating a longer ogive length 104 than would otherwise fit in a conventional neck having only the interference diameter 64.
In any of the disclosed embodiments, at least a portion of the projectile 100 is coextensive with both the interference band 58 and the clearance band 60, 560. In certain embodiments, the projectile 100 is not in contact with the clearance band 60, 560 (i.e., clearance fit). In embodiments, the projectile 100 comprises the exterior surface 114 that does not conform in shape to the clearance band 60, 560. In other embodiments, the exterior surface partially conforms to the clearance band 60, 560 and/or the transition 62, but does not touch the entire length 68 of clearance band 60.
In certain embodiments, the mouth 90 is spaced from the exterior surface 114 of the projectile 100 to form a mouth gap 94. In such embodiments, a sealant 98 may be provided between the mouth 90 and the projectile 100. Applicable sealants include UV-cured sealants, or anaerobic sealants, other wicking sealants, or other waterproofing sealants, and any other sealant used for this purpose in the cartridge field.
In embodiments with a clearance fit for the clearance band 60, 560, a radial gap 96 is formed between the interior surface 582 of the clearance band 560 and the exterior surface 114 of the projectile 100. In certain embodiments, the radial gap is about 0.001-0.005″. In embodiments with or without a mouth 90, a sealant may be provided at the radial gap 96 between the clearance band 60, 560 and the projectile 100 in the same manner as sealant 98.
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In some embodiments, the cartridge 20 conforms to standardized dimensions, for example dimensions established by the Sporting Arms and Ammunition Manufacturers' Institute, Inc. (SAAMI). The standardized dimensions cover both a cartridge and corresponding firearm with acceptable tolerance ranges, for example a neck diameter and a chamber diameter. It will be appreciated that embodiments of the two-stage neck 32 of the present disclosure will provide the exterior clearance diameter 88 that is less than the smallest possible chamber diameter of the tolerance range for a given standardized cartridge. Accordingly, in embodiments, the case 22 is configured for a cartridge of standardized cartridge dimensions comprising a predetermined projectile diameter and the interference diameter 64 of the interference band 58 is less than the predetermined projectile diameter and the clearance diameter 80 of the clearance band 60 is slightly less than, equal to, or greater than the predetermined projectile diameter, but the exterior diameter 88 of the clearance band 60 must remain smaller than the chamber diameter. As one example, the SAAMI specifications for a 308 Winchester include maximum cartridge neck diameter of 0.3435″ at the mouth while the minimum chamber diameter is 0.3442″ at the mouth, therefore corresponding clearance band 60 will have an exterior diameter 88 that must be less than 0.3442″ but may be greater than 0.3435″. In embodiments, the neck length 52 remains in conformance with the standardized cartridge dimensions.
Embodiments of the present disclose provide a method for forming a case 22 (e.g., an ammunition case). In embodiments, the method comprises drawing and forming a body, a base at one end of the body, and a neck at an opposite end of the body, the neck comprising: a neck length extending from the body to a terminal edge, an exterior surface, and an interior surface comprising an interference diameter; and increasing the interior surface of the neck to form a clearance band comprising a clearance diameter greater than the interference diameter, wherein the expanding is performed along about 15% to about 85% of the neck length.
In certain embodiments, the increasing step is performed by punching the neck with a die. For example, after the neck is formed with an inner diameter equal to the interference diameter 64, a punch having an outer diameter equal to the clearance diameter 80 is driven axially into the neck. The depth of the punch provides the clearance length 84 of the clearance band 60. In other embodiments, the increasing step is performed by boring out the two-stage neck 32 in the desired location of the clearance band 60.
Case materials applicable to the present disclosure include metals and non-metals. Some embodiments of the case 22 are formed from a high-strength metal such as brass, steel, steel alloys, steel-boron alloys, high-strength aluminum, and the like. In embodiments, the case 22 is formed of a steel-boron alloy comprising about 0.001%-0.500% boron by weight, other steel-boron alloys comprise less than about 0.500% boron by weight, less than about 0.400% boron by weight, less than about 0.300% boron by weight, less than about 0.200% boron by weight, less than about 0.100% boron by weight, about 0.001-0.100%, about 0.001-0.050%, about 0.001-0.010%, and about 0.001-0.005%. Various other case materials are also contemplated herein, such as, for example, as disclosed in U.S. Patent Application Publication No. 2022/0097124, filed Sep. 24, 2021, entitled BORON STEEL HIGH-PRESSURE CARTRIDGE CASE, which is hereby incorporated by reference herein in its entirety.
In some embodiments, relative to a conventional brass case, the greater rigidity and modulus of elasticity in high-strength metals may provide functional benefits but may also have a significant impact on retention force. Many conventional arrangements of a cylindrical neck for a brass case rifle cartridge yield retention forces that are less than or equal to about 150 pounds of force (1bf), whereas a steel alloy case with the same design (including the same neck design) can yield retention forces that are 3-4× greater and significantly higher muzzle energy. By contrast, embodiments of the present disclosure provide the benefits of a high-strength case with comparable retention force to brass. In embodiments of the present disclose comprising a case 22 formed of a high-strength metal, e.g., steel or boron-steel, the two-stage neck 32 provides a retention force comparable to brass, in particular a retention force of about 25-150 1bf on the projectile, less than or equal to about 150 1bf, less than or equal to about 200 1bf, or less than or equal to about 250 1bf.
The disclosed embodiments may be beneficial for using steel or other relatively high-strength materials for the case 22 with retention forces that are comparable to brass. Such high-strength case materials may offer strength, cost, and manufacturability benefits as compared to conventional configurations and materials, particularly for modern military applications. Nonetheless, applicable embodiments of case materials also include brass or other relatively low-strength materials.
As discussed above, in certain embodiments, the clearance band 60 may preclude the need for a mouth 90 or reduce the amount of mouth flare required for proper assembly and seating of the projectile 100. This may provide various benefits, such as utilizing less ductile metals and/or simpler manufacturing processes. In a similar manner, the design of the interference band 58 may be tuned to a desired interference retention force that precludes or reduces the need for crimping after the projectile is seated. Because forming a mouth and/or crimp strain the metallic material and damage the integrity of the surface (for example, a plated surface), embodiments of the present disclose provide improved surface integrity for the interior and exterior surfaces of the two-stage neck 32. As a result, the two-stage neck 32 may be less susceptible to corrosion than conventional designs, which may obviate the need for costly material choices or corrosion mitigation manufacturing steps
Various modifications to the above examples are contemplated to be within the scope of the present disclosure. The various angled or curved surfaces of the transition 62, interior surface 82 of the clearance band 60, mouth 90 may be varied without departing from the scope of the disclosure. The case 22 may have various modifications in the body 24, shoulder 34, and/or base 36.
Embodiments of the present disclosure are applicable to various types, sizes, and uses of ammunition cartridges. For example, the two-stage neck 32 may be implemented for casings of typical military cartridges such as 5.56 mm NATO, 6.5 mm, 6.8 mm, 7.62 mm NATO, 338 cal., and .50 BMG. In embodiments, projectiles may be lead, lead-free, jacketed, or non-jacketed. The present disclosure may also be applicable to centerfire as well as rimfire cartridges, as well as various types of firearms including handguns, rifles, semiautomatics, automatics, combinations thereof, and the like. Applicable rifles may include match, sporting, and shotgun styles.
All of the features disclosed, claimed, and incorporated by reference herein, and all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is an example only of a generic series of equivalent or similar features. Inventive aspects of this disclosure are not restricted to the details of the foregoing embodiments, but rather extend to any novel embodiment, or any novel combination of embodiments, of the features presented in this disclosure, and to any novel embodiment, or any novel combination of embodiments, of the steps of any method or process so disclosed.
Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose could be substituted for the specific examples disclosed. This application is intended to cover adaptations or variations of the present subject matter. Therefore, it is intended that the invention be defined by the attached claims and their legal equivalents, as well as the illustrative aspects. The above described embodiments are merely descriptive of its principles and are not to be considered limiting. Further modifications of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the inventive aspects.
This application claims the benefit of U.S. Provisional Patent Application No. 63/329,870, filed Apr. 11, 2022, entitled REDUCED TENSION CARTRIDGE CASE WITH TWO-STAGE NECK, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63329870 | Apr 2022 | US |
